Faculty Profiles - HAYAKAWA Satoshi

Papers - HAYAKAWA Satoshi

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Improvement of caffeine adsorption on octacalcium phosphate through suberate ion incorporation

Takuya Kataoka, Ayumi Koga, Seita Nishiyama, Tomohiko Yoshioka, Satoshi Hayakawa

Materials Letters 385 138188 - 138188 2025.4

Comparative study of the effects of fluoride treatment with cyclic variations in pH on the structures of stoichiometric, calcium-deficient, and carbonated hydroxyapatites

Satoshi Hayakawa, Yu Okada, Tomohiko Yoshioka

Journal of the Ceramic Society of Japan 133 ( 1 ) 15 - 24 2025.1

Electrochemically assisted sol-gel deposition of bioactive gels for biomedical applications Reviewed

Tomohiko Yoshioka, Naoki Miyamoto, Satoshi Hayakawa

Journal of Sol-Gel Science and Technology 112 ( 2 ) 419 - 424 2024.9

Authorship：Last author Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

So far, the sol-gel process has been available to prepare precursor gels of bioactive glasses with various compositions. In this report, we described a novel coating method of bioactive gels on a titanium substrate where the sol-gel transition is controlled by applying external electric fields. The application of a constant current of 10 mA/cm² in an acidic sol containing pre-hydrolyzed tetraethoxysilane, calcium nitrate, and ammonium dihydrogen phosphate led to the deposition of gels on the titanium cathodes due to the generation of OH^– by water electrolysis as a catalyst of the sol-gel transition. The obtained gels, which were characterized to be amorphous and consisted of Si, Ca, and P, covered the titanium substrates as a coating. The bioactivity of the gels deposited was confirmed by soaking in a simulated body fluid (SBF) up to 7 days, suggesting that the electrochemically assisted sol-gel process is promising for providing bioactive coatings on metallic implants.

Graphical Abstract

DOI： 10.1007/s10971-024-06530-6

Other Link： https://link.springer.com/article/10.1007/s10971-024-06530-6/fulltext.html

Synthesis and structural characterization of Sr(II) ion-containing octacalcium phosphate incorporated with both 2,6-pyridinedicarboxylate and succinate ions as a bone defect filler with multiple drug loading capability Reviewed

Takuya Kataoka, Seita Nishiyama, Eiji Fujii, Tomohiko Yoshioka, Satoshi Hayakawa

Colloids and Surfaces A: Physicochemical and Engineering Aspects 134001 - 134001 2024.4

Effect of chitosan content on protein adsorption capacity of Mg(II) ion-containing apatite/chitosan composite particles Reviewed

Takuya Kataoka, Wataru Nishizaki, Yuhi Yasuhira, Eiji Fujii, Tomohiko Yoshioka, Satoshi Hayakawa

Journal of the Ceramic Society of Japan 2024

Incorporation behavior of Mg(II) ion into hydroxyapatite in the presence of chitosan Reviewed

Takuya Kataoka, Yuhi Yasuhira, Eiji Fujii, Tomohiko Yoshioka, Satoshi Hayakawa

Journal of the Ceramic Society of Japan 131 ( 9 ) 569 - 574 2023.9

Functional evaluation of mineral trioxide aggregate cement with choline dihydrogen phosphate. Reviewed

Kazuhisa Tabira, Noboru Kajimoto, Hirogo Minamisawa, Taira Sato, Michito Maruta, Kyoko Oka, Takuya Kataoka, Tomohiko Yoshioka, Satoshi Hayakawa, Kanji Tsuru

Dental materials journal 2023.4

Language：English Publishing type：Research paper (scientific journal)

To improve the cytocompatibility of mineral trioxide aggregate (MTA) cement and its ability for reparative dentin formation, the effect of adding choline dihydrogen phosphate (CDHP), which is reported to be biocompatible, to MTA cement was investigated. The L929 cell proliferation showed that the addition of CDHP improved cell viability. The addition of CDHP shortened the setting time of MTA cement, with a significant decrease in consistency above 0.4 g/mL. Diametral tensile strength of the set cement was improved by the addition of 0.4 g/mL CDHP. Solubility was judged to be within the range of clinical application. The spontaneous precipitation of low crystalline hydroxyapatite was examined by immersing the set cement in phosphate buffer saline, and it was found that the ability of the cement with 0.4 g/mL of CDHP was significantly improved compared with that of the cement without CDHP.

DOI： 10.4012/dmj.2022-283

Effects of the silicon-containing chemical species dissolved from chitosan–siloxane hybrids on nerve cells Reviewed

Kosei Hattori, Satoshi Hayakawa, Yuki Shirosaki

Journal of Sol-Gel Science and Technology 104 ( 3 ) 606 - 616 2022.12

Publishing type：Research paper (scientific journal)

Silicic acid components from bioactive glass activate osteoblasts gene for bone generation. Many studies have been reported on osteoblast compatibility and bone regeneration using composites and hybrids, including silica or siloxane units. We previously synthesized chitosan−siloxane hybrids via a sol-gel method and observed bone and nerve regeneration. However, it is not clear the structure of molecules involving silicon atoms that has a more effective role in the cell activity and their mechanisms of cell activation. In this study, we prepared hybrid materials from chitosan and different types of alkoxysilane, 3-glycidoxypropyltrimethoxysilane (GPTMS), 3-glycidoxypropyldimethoxymethylsilane (GPDMS), and tetraethoxysilane (TEOS), and investigated the structures of the silicon-containing species dissolved from each hybrid and their effect on the proliferation of nerve cells. The silicon-containing species in the extraction were mainly 100–600 molecular weight, indicating they were chitin/chitosan units and monomeric hydrolyzed GPTMS, GPDMS, and TEOS. The nerve cell proliferation was inhibited by the chitosan–GPTMS and GPDMS hybrid extractions. The silicon-containing species were not taken up by the cells. The silicon-containing species dissolved from the hybrids were adsorbed to the cells or they inactivated biomolecules in the culture medium, suppressing cell proliferation. [Figure not available: see fulltext.]

DOI： 10.1007/s10971-022-05814-z

Preparation and Drug Release Profile of Chitosan–Siloxane Hybrid Capsules Coated with Hydroxyapatite Reviewed

Yuki Shirosaki, Yasuyo Tsukatani, Kohei Okamoto, Satoshi Hayakawa, Akiyoshi Osaka

Pharmaceutics 14 ( 5 ) 2022.5

Publishing type：Research paper (scientific journal)

Chitosan is a cationic polymer that forms polymerized membranes upon reaction with anionic polymers. Chitosan−carboxymethyl cellulose (CMC) capsules are drug delivery carrier candidates whose mechanical strength and permeability must be controlled to achieve sustained release. In this study, the capsules were prepared from chitosan−γ-glycidoxypropyltrimethoxysilane (GPTMS)−CMC. The mechanical stability of the capsules was improved by crosslinking the chitosan with GPTMS. The capsules were then coated with hydroxyapatite (HAp) by alternately soaking them in calcium chloride solution and disodium hydrogen phosphate solution to prevent rapid initial drug release. Cytochrome C (CC), as a model drug, was introduced into the capsules via two routes, impregnation and injection, and then the CC released from the capsules was examined. HAp was found to be deposited on the internal and external surfaces of the capsules. The amount of CC introduced, and the release rate were reduced by the HAp coating. The injection method was found to result in the greatest CC loading.

DOI： 10.3390/pharmaceutics14051111

Antibacterial Chitosan Nanofiber Thin Films with Bacitracin Zinc Salt. Reviewed International journal

Kazutaka Kumamoto, Toshinari Maeda, Satoshi Hayakawa, Nurul Asyifah Binti Mustapha, Meng-Jiy Wang, Yuki Shirosaki

Polymers 13 ( 7 ) 2021.3

Language：English Publishing type：Research paper (scientific journal)

Chitosan nanofiber has a highly uniform structure of 20-50 nm in diameter and shows high dispersibility in water due to its submicron size and high surface-to-volume ratio. The stacked nanofibers film is useful for breathability because it has a gap with a size of several tens of nm or more. However, the chemical bonds between the nanofibers cannot be broken during use. In this study, the thin films were obtained by filtration of chitosan nanofibers and 3-glycidoxypropyltrimethoxysilane (GPTMS) mixture. The addition of GPTMS changed the wettability, mechanical property and stability in water of the thin films. Bacitracin zinc salt (BZ) has been used for the localized dermatological medicines and loaded in the films. BZ interacted electrostatically with the thin films matrix and the release of BZ was controlled by the amount of GPTMS. A higher released amount of BZ showed higher antibacterial effects toward S. aureus. The film was also tested their toxicity by L929 fibroblasts. The release of less than 11.9 μg of BZ showed antibacterial effects, but were not toxic for fibroblast cells.

DOI： 10.3390/polym13071104

Blood-compatible ceramic particles, coating layers, and macrospheres for blood purification and related applications

Takuji Asano, Tomohiko Yoshioka, Yuki Shirosaki, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Bioceramics 195 - 243 2021

Three-dimensional observation and analysis of remineralization in dentinal caries lesions Reviewed

Kumiko Yoshihara, Noriyuki Nagaoka, Akiko Nakamura, Toru Hara, Satoshi Hayakawa, Yasuhiro Yoshida, Bart Van Meerbeek

Scientific Reports 10 ( 1 ) 2020.12

Conversion of sub-µm calcium carbonate (calcite) particles to hollow hydroxyapatite agglomerates in K2HPO4 solutions Reviewed

Sun Yanyan, Wang Guangxin, Li Wuhui, Wang Yaming, Satoshi Hayakawa, Akiyoshi Osaka

Nanotechnology Reviews 9 ( 1 ) 945 - 960 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Walter de Gruyter GmbH

<title>Abstract</title>
Sub-µm CaCO₃ (calcite; CC) particles were converted to calcium monohydrogenphosphate dihydrate (DCPD) and hydroxyapatite (HAp) via soaking treatments in K₂HPO₄ solutions with varied pH (3–12) and concentrations (0.1–1.5 M) at 37°C for up to 10 days. DCPD was derived from the solutions with pH ≤ 6; while hollow HAp was yielded when pH ≥ 7 in assemblies of petal-like crystallites. Results of magic angle spinning (MAS) and cross-polarization magic angle spinning (CP-MAS) NMR studies have shown that the HAp lattice has only PO₄
²⁻ but no HPO₄
²⁻ at B (phosphate) sites. Trace amounts of CO₃
²⁻ have occupied both A (OH) and B (PO₄) sites, and H₂O is adsorbed on surface crystallites. The primary crystallite size of HAp derived from Scherrer equation increases quickly in a 12 h period and becomes gradually stable afterward. Samples of particles soaked within 3 h in a temperature range of 20–80°C were analyzed by X-ray diffraction. It is shown that the rate constant of 1 M solution is about an order of magnitude greater than that of 0.1 M solution and the apparent activation energy is 33 kJ/mol. In this work, the conversion of CC to HAp can be quantitatively controlled to solve the problem of slow degradation of HAp.

DOI： 10.1515/ntrev-2020-0070

Other Link： https://www.degruyter.com/document/doi/10.1515/ntrev-2020-0070/xml

Comparative study of in vitro apatite-forming abilities of highly ordered rutile nanorod arrays fabricated on cpTi and Ti6Al4V alloys Reviewed

Xingzhu Liu, Tomohiko Yoshioka, Satoshi Hayakawa

Journal of Asian Ceramic Societies 8 ( 1 ) 29 - 38 2020.1

Cytocompatible and antibacterial properties of chitosan−siloxane hybrid spheres Reviewed

Yuki Shirosaki, Manato Nakatsukasa, Saki Yasutomi, Susana Cruz-Neves, Satoshi Hayakawa, Akiyoshi Osaka, Toshinari Maeda, Toshiki Miyazaki

Polymers 11 1676 - 1686 2019.10

Effect of titanyl sulfate concentration on growth of nanometer-scale rutile rod arrays on the surface of titanium substrate Reviewed

Xing-zhu LIU, Tomohiko YOSHIOKA, Satoshi HAYAKAWA

Journal of the Ceramic Society of Japan 127 ( 8 ) 545 - 550 2019.8

The fabrication of nanostructured titania polymorphs layer with high crystallinity and its apatite-forming ability Reviewed

Xingzhu Liu, Fan Xiao, Satoshi Hayakawa, Akiyoshi Osaka

Surface and Coatings Technology 363 338 - 343 2019.4

© 2019 Elsevier B.V. High crystallinity anatase/rutile layers are prepared on the surface of commercially pure titanium (cpTi) by hydrothermal method at 160 °C for 3 h. The surface morphology of titania layers is changed by adjusting the pH value and Ti 4+ concentration of treating solution (TS). Obtained nanorods on all TS samples are composed of pure rutile and the anatase co-deposited with rutile is found in the dense bottom layer. The possible co-deposition mechanism of polymorphs layers is given in this study. In this study, the rutile nanorods array with high energy (101) facet exposed is found on the TS 3 sample. In vitro apatite forming ability of the TS samples are confirmed by soaking them in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 °C) for 1 and 3 days. Results show that apatite particles could be obtained on all TS samples within 1 d. After 3 days' immersion in SBF, TS 3 sample shows strongest apatite X-ray diffraction. These results indicate that the ability in inducing apatite on cpTi with TS 3 treatment is excellent. Such excellent apatite-forming ability is ascribed to the existence of thick titania layer with high energy (101) facet exposed on the TS 3 sample.

DOI： 10.1016/j.surfcoat.2019.02.063

Accelerated induction of in vitro apatite formation by parallel alignment of hydrothermally oxidized titanium substrates separated by sub-millimeter gaps Reviewed

Satoshi Hayakawa, Keigo Okamoto, Tomohiko Yoshioka

Journal of Asian Ceramic Societies 7 ( 1 ) 90 - 100 2019.1

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Informa UK Limited

© 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of The Korean Ceramic Society and The Ceramic Society of Japan. Although autoclaving is a common sterilization method for biomedical devices, the ability to induce deposition of apatite particles on hydrothermally treated titanium is still not fully realized. This is because the induction ability is too weak to be evaluated via in vitro apatite formation in Kokubo’s simulated body fluid (SBF) by the conventional immersion method, i.e. using samples with open and smooth surface. This study reports on the surface structure of hydrothermally treated titanium and the ability to induce deposition of apatite particles on the surface of parallel confined spaces separated by sub-millimeter gaps in Kokubo’s SBF. Thin-film X-ray diffraction and analyses using Fourier transform infra-red (FT-IR) spectroscopy and Raman spectroscopy revealed that a nano-crystalline anatase-type titanium oxide layer was formed on titanium substrates after hydrothermal treatment at 150°C for 2 h. When growth of the titanium oxide layer was moderately suppressed, the hydrothermally treated titanium surface exhibited a characteristic interference color, silver or gold, which does not impair the esthetic appearance of the titanium-based implant. The ability to induce deposition of apatite particles on hydrothermally treated titanium was remarkably amplified by parallel alignment of substrates separated by sub-millimeter gaps.

DOI： 10.1080/21870764.2019.1572690

Atomic level observation and structural analysis of phosphoric-acid ester interaction at dentin Reviewed International journal

Kumiko Yoshihara, Noriyuki Nagaoka, Yasuhiro Yoshida, Bart Van Meerbeek, Satoshi Hayakawa

Acta Biomaterialia 97 544 - 556 2019.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 Acta Materialia Inc. The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), used in many dental adhesives, self-assembles in nano-layers at adhesive-tooth interfaces. Recently, several states of the P[sbnd]OH groups of 10-MDP_Ca salts were suggested, while their actual status has not been elucidated yet. We mechanistically investigated 10-MDP_Ca-salt nano-layering at adhesive-dentin interfaces, correlatively using scanning transmission electron microscopy with energy-dispersive X-ray spectrometry (STEM-EDS), X-ray diffraction (XRD) and solid state nuclear magnetic resonance (NMR). STEM-EDS confirmed the presence of Ca and P in each nano-layer. Both XRD and NMR revealed that the two terminal P[sbnd]OH groups of 10-MDP reacted with Ca. This twofold P[sbnd]OH interaction of 10-MDP with Ca was stable in water and is therefore expected to contribute to durable nano-layering of 10-MDP_Ca salts in the hybrid and adhesive layer. Statement of Significance: The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), commonly used in dental adhesives with favorable long-term clinical outcome, has been documented to self-assemble into nano-layers at adhesive-tooth interfaces. Characterizing ultra-morphologically (STEM) and chemically (STEM-EDS, XRD, NMR) the mechanisms of interaction of 10-MDP with bulk dentin in a similar manner as what occurs clinically, it was found that the water stable 10-MDP_Ca salts consist of CaRPO4, meaning that the two [sbnd]OH groups of the phosphate group of 10-MDP ionically reacted with Ca. This stable structure is expected to contribute to durable nano-layering of 10-MDP_Ca salts in the hybrid and adhesive layer and hence to clinical longevity of the adhesively bonded tooth restoration.

DOI： 10.1016/j.actbio.2019.08.029

Conversion of silicate glass to highly oriented divalent ion substituted hydroxyapatite nanorod arrays in alkaline phosphate solutions Reviewed

Satoshi Hayakawa, Yusuke Oshita, Kazuki Yamada, Tomohiko Yoshioka, Noriyuki Nagaoka

Ceramics International 44 ( 15 ) 18719 - 18726 2018.10

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

© 2018 Elsevier Ltd and Techna Group S.r.l. This study presents a new strategy for preparing highly oriented nanorod array of divalent ion substituted hydroxyapatite (HAp) and factors controlling the rate of glass conversion. HAp nanorod arrays were prepared on a series of alkali/alkaline-earth silicate glasses in the Na2O–CaO–SrO–SiO2 system in phosphate aqueous solutions with different pH values via a glass conversion process. The effects of the substitution of Sr2+ for Ca2+ and the network connectivity (NC) of the silicate glasses on the degree of crystal orientation of the nanorod array of HAp crystals, the crystallite size, and the partial substitution of Sr2+ for Ca2+ in the HAp crystal lattice were investigated using X-ray diffraction, 29Si magic angle spinning nuclear magnetic resonance (NMR) spectroscopy, and field-emission scanning electron microscopy. Sr-free Na2O–CaO–SiO2 glass was converted into HAp nanorod arrays highly-oriented toward the c-axis, whereas the increase in the NC of the glass led to a decrease in the rate of the conversion process from glass to HAp, which resulted in the reduction of the degree of c-axis orientation of the nanorod array of the HAp crystals. However, the rate of the conversion process was remarkably promoted in alkaline phosphate solutions, resulting in an increase of the degree of c-axis orientation of the nanorod array. The Sr/(Sr + Ca) molar fraction of silicate glasses determined the molar fraction of substituted Sr2+ in HAp crystal lattice.

DOI： 10.1016/j.ceramint.2018.07.101

Etching Efficacy of Self-Etching Functional Monomers Reviewed

K. Yoshihara, S. Hayakawa, N. Nagaoka, T. Okihara, Y. Yoshida, B. Van Meerbeek

Journal of Dental Research 97 1010 - 1016 2018.8

© International & American Associations for Dental Research 2018. Besides chemically interacting with hard tooth tissue, acidic functional monomers of self-etch adhesives should etch the prepared tooth surface to dissolve the smear layer and to provide surface micro-retention. Although the etching efficacy of functional monomers is commonly determined in terms of pH, the pH of adhesives cannot accurately be measured. Better is to measure the hydroxyapatite (HAp)–dissolving capacity, also considering that functional monomers may form monomer-Ca salts. Here, the etching efficacy of 6 functional monomers (GPDM, phenyl-P, MTEGP, 4-META, 6-MHP and 10-MDP) was investigated. Solutions containing 15 wt% monomer, 45 wt% ethanol, and 40 wt% water were prepared. Initially, we observed enamel surfaces exposed to monomer solution by scanning electron microscopy (SEM). X-ray diffraction (XRD) was employed to detect monomer-Ca salt formation. Phenyl-P exhibited a strong etching effect, while 10-MDP–treated enamel showed substance deposition, which was identified by XRD as 10-MDP–Ca salt. To confirm these SEM/XRD findings, we determined the etching efficacy of functional monomers by measuring both the concentration of Ca released from HAp using inductively coupled plasma–atomic emission spectroscopy (ICP-AES) and the amount of monomer-Ca salt formation using 31P magic-angle spinning (MAS) nuclear magnetic resonance (NMR). ICP-AES revealed that the highest Ca concentration was produced by phenyl-P and the lowest Ca concentration, almost equally, by 4-META and 10-MDP. Only 10-MDP formed 10-MDP–Ca salts, indicating that 10-MDP released more Ca from HAp than was measured by ICP-AES. Part of the released Ca was consumed to form 10-MDP–Ca salts. It is concluded that the repeatedly reported higher bonding effectiveness of 10-MDP–based adhesives must not only be attributed to the more intense chemical bonding of 10-MDP but also to its higher etching potential, a combination the other functional monomers investigated lack.

DOI： 10.1177/0022034518763606

Chemical interaction of glycero-phosphate dimethacrylate (GPDM) with hydroxyapatite and dentin Reviewed

Kumiko Yoshihara, Noriyuki Nagaoka, Satoshi Hayakawa, Takumi Okihara, Yasuhiro Yoshida, Bart Van Meerbeek

Dental Materials 34 ( 7 ) 1072 - 1081 2018.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Inc.

Objectives: Although the functional monomer glycero-phosphate dimethacrylate (GPDM) has since long been used in several dental adhesives and more recently in self-adhesive composite cements and restoratives, its mechanism of chemical adhesion to hydroxyapatite (HAp) is still unknown. We therefore investigated the chemical interaction of GPDM with HAp using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin. Methods: HAp particles were added to a GPDM solution for various periods, upon which they were thoroughly washed with ethanol and water prior to being air-dried. As control, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was used. The molecular interaction of GPDM with HAp was analyzed using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Crystal formation upon application of GPDM onto dentin was analyzed using thin-film XRD (TF-XRD). Its hydrophobicity was measured using contact-angle measurement. The interaction of GPDM with dentin was characterized using transmission electron microscopy (TEM). Results: XRD revealed the deposition of dicalcium phosphate dihydrate (DCPD: CaHPO4·2H2O) on HAp after 24 h. NMR confirmed the adsorption of GPDM onto HAp. However, GPDM was easily removed after washing with water, unlike MDP that remained adhered to HAp. Dentin treated with GPDM appeared more hydrophilic compared to dentin treated with MDP. TEM disclosed exposed collagen in the hybrid layer produced by the GPDM-based primer formulation. Significance: Although GPDM adsorbed to HAp, it did not form a stable calcium salt. The bond between GPDM and HAp was weak, unlike the strong bond formed by MDP to HAp. Due to its high hydrophilicity, GPDM might be an adequate monomer for an etch-and-rinse adhesive, but appears less appropriate for a ‘mild’ self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material.

DOI： 10.1016/j.dental.2018.04.003

Characterization and degradation study of chitosan-siloxane hybrid microspheres synthesized using a microfluidic approach Reviewed

Susana Cruz-Neves, Yuki Shirosaki, Toshiki Miyazaki, Satoshi Hayakawa

MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS 81 571 - 579 2017.12

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Chitosan microspheres can address challenges associated with poor bioavailability or unsustained drug release when used as drug delivery systems thanks to their mucoadhesiveness, which allows the drug dosage to be retained in the gastrointestinal track for extended periods. Chitosan-3-glycidoxypropyltrimethoxysilane-beta-glycerophosphate (chitosan-GPTMS-beta-GP) hybrid microspheres were synthetized through sol-gel processing using a microfluidic approach. Microspheres with uniform spherical shapes and sizes of approximately 650 pm were obtained. The microstructures of the microspheres consisted of four different siloxane structures. The degradation behaviors of the hybrid microspheres were examined under acidic pH conditions mimicking those found in the gastrointestinal track. Microspheres with different GPTMS molar ratios were incubated under several pH conditions for 2 weeks. The microspheres incubated at pH 7.4 extended the lowest weight loss (27%-32%), whereas those incubated at pH 1.7 and pH 5.4 showed greater weight losses of 43-59% and 69-77%, respectively. The inhibition of the degradation at low pH was dependent on the siloxane network in the chitosan matrix. Phosphate was mostly released in early stages, and the released amount of silicon was dependent on the composition. GPTMS was released with a chitosan chain via the hydrolysis of a chitosan molecule. The pelargonidin was incorporated in the microspheres and the slow releasing was observed at acidic condition. The resistance of these hybrid microspheres to low-pH conditions for longer than a full digestion cycle is promising for gastrointestinal drug delivery applications.

DOI： 10.1016/j.msec.2017.08.035

Preparation of chitosan-hydroxyapatite composite mono-fiber using coagulation method and their mechanical properties Reviewed

Takuma Okada, Yuta Nobunaga, Toshiisa Konishi, Tomohiko Yoshioka, Satoshi Hayakawa, Maria Ascensao Lopes, Toshiki Miyazaki, Yuki Shirosaki

CARBOHYDRATE POLYMERS 175 355 - 360 2017.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Autograft has been carried out for anterior cruciate ligament (ACL) reconstruction surgery. However, it has negative aspect because patients lose their healthy ligaments from other part. We focus on a chitosan-hydroxyapatite (HAp) composite fiber as a scaffold of ligament regeneration. Chitosan- HAp composite fiber was made by using coagulation method. Chitosan-NaH2PO4 solution was coagulated with coagulation bath including calcium ion to get the mono-fiber and then treated with sodium hydroxide solution to form HAp in fiber matrix. The mechanical property of the fiber was improved by the stretching of the wet one because of the orientation of chitosan molecule and the interaction between chitosan and HAp. Maximum stress was improved with increasing of sodium dihydrogen phosphate until 0.03 M. The swelling ratio of the fiber was inhibited by composited with HAp. Additionally, bone-bonding ability was confirmed by SBF soaking tests. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbpol.2017.07.072

Hydroxyapatites: Key Structural Questions and Answers from Dynamic Nuclear Polarization Reviewed

Cesar Leroy, Fabien Aussenac, Laure Bonhomme-Coury, Akiyoshi Osaka, Satoshi Hayakawa, Florence Babonneau, Cristina Coelho-Diogo, Christian Bonhomme

ANALYTICAL CHEMISTRY 89 ( 19 ) 10201 - 10207 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We demonstrate that NMR/DNP (Dynamic Nuclear Polarization) allows an unprecedented description of carbonate substituted hydroxyapatite (CHAp). Key structural questions related to order/disorder and clustering of carbonates are tackled using distance sensitive DNP experiments using C-13-C-13 recoupling. Such experiments are easily implemented due to unprecedented DNP gain (orders of magnitude). DNP is efficiently mediated by quasi one-dimensional spin diffusion through the hydroxyl columns present in the CHAp structure (thought of as "highways" for spin diffusion). For spherical nanoparticles and phi < 100 nm, it is numerically shown that spin diffusion allows their study as a whole. Most importantly, we demonstrate also that the DNP study at 100 K leads to data which are comparable to data obtained at room temperature (in terms of spin dynamics and line shape resolution). Finally, all 2D DNP experiments can be interpreted in terms of domains exhibiting well identified types of substitution: local order and carbonate clustering are clearly favored.

DOI： 10.1021/acs.analchem.7b01332

Chemical interaction mechanism of 10-MDP with zirconia

Noriyuki Nagaoka, Kumiko Yoshihara, Victor Pinheiro Feitosa, Yoshiyuki Tamada, Masao Irie, Yasuhiro Yoshida, Bart Van Meerbeek, Satoshi Hayakawa

SCIENTIFIC REPORTS 7 2017.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using H-1 and P-31 magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) H-1 -> P-31 heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. P-31-NMR revealed that one P-OH non-deprotonated of the PO3H2 group from 10-MDP chemically bonded strongly to zirconia. H-1-P-31 HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O-). The combination of H-1 NMR and 2D H-1-P-31 HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia.

DOI： 10.1038/srep45563

Alternating Current Electrophoretic Deposition for the Immobilization of Antimicrobial Agents on Titanium Implant Surfaces Reviewed

Annabel Braem, Katrijn De Brucker, Nicolas Delattin, Manuela S. Killian, Maarten B. J. Roeffaers, Tomohiko Yoshioka, Satoshi Hayakawa, Patrik Schmuki, Bruno P. A. Cammue, Sannakaisa Virtanen, Karin Thevissen, Bram Neirinck

ACS APPLIED MATERIALS & INTERFACES 9 ( 10 ) 8533 - 8546 2017.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

One prominent cause of implant failure is infection; therefore, research is focusing on developing surface coatings that render the surface resistant to colonization by micro-organisms. Permanently attached coatings of antimicrobial molecules are of particular interest because of the reduced cytoxicity and lower risk of developing resistance compared to controlled release coatings. In this study, we focus on the chemical grafting of bioactive molecules on titanium. To concentrate the molecules at the metallic implant surface, we propose electrophoretic deposition (EPD) applying alternating current (AC) signals with an asymmetrical wave shape. We show that for the model molecule bovine serum albumin (BSA), as well as for the clinically relevant antifungal lipopeptide caspofungin (CASP), the deposition yield is drastically improved by superimposing a DC offset in the direction of the high-amplitude peak of the AC signal. Additionally, in order to produce immobilized CASP coatings, this experimental AC/DC-EPD method is combined with an established surface activation protocol. Principle component analysis (PCA) of time of-flight secondary ion mass spectrometry (ToF-SIMS) data confirm the immobilization of CASP with higher yield as compared to a diffusion-controlled process, and higher purity than the clinical CASP starting suspensions. Scratch testing data indicate good coating adhesion. Importantly, the coatings remain active against the fungal pathogen C. albicans as shown by in vitro biofilm experiments. In summary, this paper delivers a proof-of-concept for the application of AC-EPD as a fast grafting tool for antimicrobial molecules without compromising their activities.

DOI： 10.1021/acsami.6b16433

Challenging of nerve regeneration using chitosan-siloxane hybrids

Shirosaki Yuki, Hayakawa Satoshi, Osaka Akiyoshi, Lopes Maria, Santos Jose, Mauricio Ana, Geuna Stefano

Transactions of Japanese Society for Medical and Biological Engineering 54 ( 27 ) S170 - S170 2016

Language：Japanese Publisher：Japanese Society for Medical and Biological Engineering

<p>Many studies have been dedicated to the development of scaffold for improving post-traumatic nerve regeneration. Biodegradable chitosan-siloxane porous hybrid membranes were very flexible and have interconnected pores to be excellent cytocompatibility for osteoblastic cells, fibroblastic cells, and nerve cells. In this study, chitosan-siloxane porous hybrid membranes were used to regenerate nerve tissue with or without some cells after crush injury. The regeneration in terms of Schwann cell proliferation, axon elongation and myelination was promoted with the hybrids. Combination with mesenchymal stem cells. The good regenerated nerve improved the the degree of functional recovery such as the extensor postural thrust and the withdrawal reflex latency.</p>

DOI： 10.11239/jsmbe.54Annual.S170

Functional monomer impurity affects adhesive performance Reviewed

Kumiko Yoshihara, Noriyuki Nagaoka, Takumi Okihara, Manabu Kuroboshi, Satoshi Hayakawa, Yukinori Maruo, Goro Nishigawa, Jan De Munck, Yasuhiro Yoshida, Bart Van Meerbeek

DENTAL MATERIALS 31 ( 12 ) 1493 - 1501 2015.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Objective. The functional monomer 10-MDP has been considered as one of the best performing functional monomers for dental adhesives. Different adhesives containing 10-MDP are commercially available, among which many so-called 'universal' adhesives. We hypothesize that the quality of the functional monomer 10-MDP in terms of purity may affect bonding performance.
Methods. We therefore characterized three different 10-MDP versions (10-MDP_KN provided by Kuraray Noritake; 10-MDP_PCM provided by PCM; 10-MDP_DMI provided by DMI) using NMR, and analyzed their ability to form 10-MDP_Ca salts on dentin using XRD. The 'immediate' and 'aged' micro-tensile bond strength (mu TBS) to dentin of three experimental 10-MDP primers was measured. The resultant interfacial adhesive-dentin ultra-structure was characterized using TEM.
Results. NMR disclosed impurities and the presence of 10-MDP dimer in 10-MDP_PCM and 10-MDP_DMI. 10-MDP_PCM and 10-MDP_DMI appeared also sensitive to hydrolysis. 10-MDP_KN, on the contrary, contained less impurities and dimer, and did not undergo hydrolysis. XRD revealed more intense 10-MDP_Ca salt deposition on dentin induced by 10-MDP_KN. The adhesive based on the experimental 10-MDP_KN primer resulted in a significantly higher 'immediate' bond strength that remained stable upon aging; the mu TBS of the experimental 10-MDP_PCM and 10-MDP_DMI adhesives significantly dropped upon aging. TEM revealed thicker hybridization and more intense nano-layering for 10-MDP_KN.
Significance. It was concluded that primer impurities and the presence of 10-MDP dimer affected not only hybridization, but also reduced the formation of 10-MDP_Ca salts and nano-layering. 10-MDP in a high purity grade is essential to achieve durable bonding. (C) 2015 Published by Elsevier Ltd on behalf of Academy of Dental Materials. All rights reserved.

DOI： 10.1016/j.dental.2015.09.019

Interlaboratory studies on in vitro test methods for estimating in vivo resorption of calcium phosphate ceramics Reviewed

Atsuo Ito, Yu Sogo, Atsushi Yamazaki, Mamoru Aizawa, Akiyoshi Osaka, Satoshi Hayakawa, Masanori Kikuchi, Kimihiro Yamashita, Yumi Tanaka, Mika Tadokoro, Lidia Agata de Sena, Fraser Buchanan, Hajime Ohgushi, Marc Bohner

ACTA BIOMATERIALIA 25 347 - 355 2015.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

A potential standard method for measuring the relative dissolution rate to estimate the resorbability of calcium-phosphate-based ceramics is proposed. Tricalcium phosphate (TCP), magnesium-substituted TCP (MgTCP) and zinc-substituted TCP (ZnTCP) were dissolved in a buffer solution free of calcium and phosphate ions at pH 4.0, 5.5 or 7.3 at nine research centers. Relative values of the initial dissolution rate (relative dissolution rates) were in good agreement among the centers. The relative dissolution rate coincided with the relative volume of resorption pits of ZnTCP in vitro. The relative dissolution rate coincided with the relative resorbed volume in vivo in the case of comparison between microporous MgTCPs with different Mg contents and similar porosity. However, the relative dissolution rate was in poor agreement with the relative resorbed volume in vivo in the case of comparison between microporous TCP and MgTCP due to the superimposition of the Mg-mediated decrease in TCP solubility on the Mg-mediated increase in the amount of resorption. An unambiguous conclusion could not be made as to whether the relative dissolution rate is predictive of the relative resorbed volume in vivo in the case of comparison between TCPs with different porosity. The relative dissolution rate may be useful for predicting the relative amount of resorption for calcium-phosphate-based ceramics having different solubility under the condition that the differences in the materials compared have little impact on the resorption process such as the number and activity of resorbing cells.
Statement of significance
The evaluation and subsequent optimization of the resorbability of calcium phosphate are crucial in the use of resorbable calcium phosphates. Although the resorbability of calcium phosphates has usually been evaluated in vivo, establishment of a standard in vitro method that can predict in vivo resorption is beneficial for accelerating development and commercialization of new resorbable calcium phosphate materials as well as reducing use of animals. However, there are only a few studies to propose such an in vitro method within which direct comparison was carried out between in vitro and in vivo resorption. We propose here an in vitro method based on measuring dissolution rate. The efficacy and limitations of the method were evaluated by international round-robin tests as well as comparison with in vivo resorption studies for future standardization. This study was carried out as one of Versailles Projects on Advanced Materials and Standards (VAMAS). (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2015.07.040

Calcium phosphate crystallization on titania in a flowing Kokubo solution Reviewed

Satoshi Hayakawa, Kanji Tsuru, Keita Uetsuki, Keisuke Akasaka, Yuki Shirosaki, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 26 ( 8 ) 1 - 13 2015.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Dry titania layers on air-oxidized titanium substrates have been found to be active enough to cause apatite to be deposited in Kokubo's simulated body fluid (SBF) in narrow confined spaces, such as those in narrow grooves and thin gaps. Such in vitro apatite deposition is the basis of the GRAPE (R) technique. The aim of the present study is to determine why GRAPE conditions favor apatite deposition when laminar SBF flow (at 0.01-0.3 ml/min) passes through a shallow channel (0.5 mm) between a pair of titanium substrates each with a dry layer of titania. Assessing the factors that control the heterogeneous nucleation process led to the proposal of the working hypothesis that there are nucleation pre-embryos, ion assemblies that can be stabilized to form embryos, on the titania layer but that they are removed by the SBF flow. Specimens were subjected to different combinations of processes. One combination was that titania layers were exposed to still or flowing SBF, and the other was that half of a specimen, the inlet or outlet side, was exposed to still or flowing SBF with the other half being covered. The surface morphologies of the specimens were then compared in detail. The conclusion was that exposure to still SBF for 2 days before exposure to flowing SBF was required for apatite to be deposited. Some complicated apatite deposition modes were observed, e.g., apatite was deposited even on areas unexposed to still SBF. All of the results were successfully interpreted using the working hypothesis. The conclusion was that the GRAPE (R) technique depends on the confined space holding pre-embryo and embryo assemblies.

DOI： 10.1007/s10856-015-5552-x

In vitro apatite formation on nano-crystalline titania layer aligned parallel to Ti6Al4V alloy substrates with sub-millimeter gap Reviewed

Satoshi Hayakawa, Yuko Matsumoto, Keita Uetsuki, Yuki Shirosaki, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 26 ( 6 ) 2015.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Pure titanium substrates were chemically oxidized with H2O2 and subsequent thermally oxidized at 400 degrees C in air to form anatase-type titania layer on their surface. The chemically and thermally oxidized titanium substrate (CHT) was aligned parallel to the counter specimen such as commercially pure titanium (cpTi), titanium alloy (Ti6Al4V) popularly used as implant materials or Al substrate with 0.3-mm gap. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 degrees C) for 7 days. XRD and SEM analysis showed that the in vitro apatite-forming ability of the contact surface of the CHT specimen decreased in the order: cpTi > Ti6Al4V > Al. EDX and XPS surface analysis showed that aluminum species were present on the contact surface of the CHT specimen aligned parallel to the counter specimen such as Ti6Al4V and Al. This result indicated that Ti6Al4V or Al specimens released the aluminum species into the SBF under the spatial gap. The released aluminum species might be positively or negatively charged in the SBF and thus can interact with calcium or phosphate species as well as titania layer, causing the suppression of the primary heterogeneous nucleation and growth of apatite on the contact surface of the CHT specimen under the spatial gap. The diffusion and adsorption of aluminum species derived from the half-sized counter specimen under the spatial gap resulted in two dimensionally area-selective deposition of apatite particles on the contact surfaces of the CHT specimen.

DOI： 10.1007/s10856-015-5522-3

The role of hybrid chitosan membranes on scarring process following lumbar surgery: post-laminectomy experimental model Reviewed

Miguel Carvalho, Luis M. Costa, Jose E. Pereira, Yuki Shirosaki, Satoshi Hayakawa, Jose D. Santos, Stefano Geuna, Federica Fregnan, Antonio M. Cabrita, Ana C. Mauricio, Artur S. Varejao

NEUROLOGICAL RESEARCH 37 ( 1 ) 23 - 29 2015.1

Language：English Publishing type：Research paper (scientific journal) Publisher：MANEY PUBLISHING

Objectives: Post-operative scarring process on lumbar surgery is object of several studies mainly because of the epidural fibrosis formation. Hybrid chitosan have shown promising effect on fibrosis prevention. The aim of this study was to determine the influence of chitosan-silane membrane on the lumbar surgery scarring process. These membranes have improved mechanical strength which makes them suitable to maintain a predefined shape.
Methods: A two level lumbar laminectomy was performed in 14 New Zealand male rabbits. Laminectomy sites were randomly selected for biomaterial or control. Chitosan membranes were prepared and care was taken in order to make it adapted to the bone defect dimensions covering the totality of the defect including the bone margins. Histological analysis was performed by haematoxylin/eosin and by Masson's trichrome staining four weeks after laminectomy.
Results: Microscope observations revealed the presence of a well-organized regenerating tissue, integrated in the surrounding vertebral bone tissue with a regular and all-site interface on the chitosan sites, in clear contrast with the presence of a disorganized regenerating tissue with aspects consistent with the persistence of a chronic inflammatory condition, on control sites.
Discussion: The results of this study clearly demonstrated that hybrid chitosan had an organizing effect on post-operative scarring process. The presence of the hybrid chitosan membrane resulted on a well-organized tissue integrated in the surrounding vertebral bone tissue with signs of regenerative bone tissue in continuity with native bone. This can be a major feature on the dynamics of epidural fibrosis formation.

DOI： 10.1179/1743132814Y.0000000414

Preparation and in vitro cytocompatibility of chitosan-siloxane hybrid hydrogels Reviewed

Yuki Shirosaki, Masashi Hirai, Satoshi Hayakawa, Eiji Fujii, Maria A. Lopes, Jose D. Santos, Akiyoshi Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A 103 ( 1 ) 289 - 299 2015.1

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Injectable systems can be used in minimally invasive surgical applications. Although chitosan-glycerophosphate hydrogel systems are biodegradable and biocompatible, the long periods of time required for their effective gelation have severely limited their clinical application. The challenges currently facing researchers in this field are therefore focused on shortening the gelation time and biocompatibility of these materials to develop hydrogels suitable for clinical application. Chitosan and -glycidoxypropyltrimethoxysilane (GPTMS) hybrids have recently demonstrated good cytocompatibility with respect to human osteoblastic cells (MG63) and human bone marrow cells. Although these precursor sols could form gels under physiological conditions, they required neutralization with a sodium hydroxide solution. In this study, the chitosan-GPTMS hybrid systems were neutralized with glycerophosphate to prepare injectable hydrogels. The results revealed that the gelation time of the hydrogels could be controlled by the amount of GPTMS in the precursor sols. The in vitro cytocompatibility of the hydrogels were evaluated in terms of the proliferation of MG63 cells cultured either directly onto the hydrogels or indirectly onto the cell culture plate under a hydrogel insert. In the former case, the cells showed good attachment and proliferated for up to 7 days. Similar results were observed in the in direct culture. These results suggest that this new chitosan-GPTMS hydrogel could potentially be used as an injectable biomaterial in clinical applications. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 289-299, 2015.

DOI： 10.1002/jbm.a.35171

Fabrication of calcium phosphate nanoparticles in a continuous flow tube reactor Reviewed

Eiji Fujii, Koji Kawabata, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 123 ( 1435 ) 101 - 105 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Calcium phosphates (CPs) were fabricated with using a continuous flow-type tube reactor under pH 6.4 and 9, within the temperature range from 0 to 100°C. The sample fabricated at the temperature range from 0 to 60°C involved not only dicalcium hydrogenphosphate dihydrate (DCPD) as the primary phase but also octacalcium phosphate (OCP). As the relative X-ray diffraction intensity of OCP increased with increase in the synthesis temperature, particles of a sheet-like shape appeared. The samples fabricated at 80 and 100°C have a crystalline phase of hydroxyapatite (HAp) and morphology of rod-like shape. Under pH 9, in contrast, the reactor fabricated HAp crystalline, irrespective of the synthesis temperature. In particular, at 80 and 100°C, only oval or spindle-shaped HAp was yielded. It was therefore confirmed that the present tube reactor system was versatile to control the size, shape, and crystalline phase of CPs. The morphology, particle size, and specific surface area dependent on the pH and temperature of synthesis were discussed the relative stability of the relevant calcium phosphate phases and equilibrium relations among the orthophosphate ions.

DOI： 10.2109/jcersj2.123.101

Preparation of Porous Chitosan-Siloxane Hybrids Coated with Hydroxyapatite Particles Reviewed

Yuki Shirosaki, Kohei Okamoto, Satoshi Hayakawa, Akiyoshi Osaka, Takuji Asano

BIOMED RESEARCH INTERNATIONAL 2015 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：HINDAWI PUBLISHING CORPORATION

This paper describes the apatite deposition of chitosan-silicate porous hybrids derived from chitosan and gamma-glycidoxypropyltrimethoxysilane (GPTMS) in alkaline phosphate solution. The preparation of porous hybrids with needle-like apatite on their surfaces is described. Following apatite deposition the porous hybrids maintained high porosity. The enzymatic degradation rate was low even after 6 months and the porous hybrids were very flexible and cut easily using surgical scissors.

DOI： 10.1155/2015/392940

TiO2-based superhydrophobic-superhydrophilic pattern with an extremely high wettability contrast Reviewed

Shunsuke Nishimoto, Michiaki Becchaku, Yoshikazu Kameshima, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka, Michihiro Miyake

THIN SOLID FILMS 558 221 - 226 2014.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Rough nanostructured anatase TiO2 surfaces containing many pores were prepared by the hydrothermal-based method. Surface modification with self-assembled monolayers (SAMs) of octadecylphosphonic acid (ODP) resulted in the superhydrophobic surface with an extremely high static water contact angle (CA) of 173.6 degrees +/- 1.7 degrees. This superhydrophobic surface could be converted into a superhydrophilic surface with a water CA of nearly 0 degrees by irradiating it with ultraviolet (UV) light, which induced photocatalytic decomposition of the ODP SAM. A superhydrophobic-superhydrophilic pattern with an extremely high wettability contrast (a water CA difference of over 170 degrees) could be fabricated on the ODP-modified TiO2 surface by area-selective UV irradiation through a photomask. This is the report of the TiO2-based superhydrophobic-superhydrophilic pattern with a water CA difference of over 170 degrees, and it may be possible to use such patterns for various applications. (C) 2014 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.tsf.2014.02.060

Furthering the understanding of silicate-substitution in a-tricalcium phosphate: An X-ray diffraction, X-ray fluorescence and solid-state nuclear magnetic resonance study Reviewed

J. Duncan, S. Hayakawa, A. Osaka, J. F. MacDonald, J. V. Hanna, J. M. S. Skakle, I. R. Gibson

ACTA BIOMATERIALIA 10 ( 3 ) 1443 - 1450 2014.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing a-tricalcium phosphate (alpha-TCP: STO/SupTO and Si-TCP x = 0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca-3(PO4)((2-x))(SiO4)(x). Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the alpha-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and beta-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus (P-31) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupTO can resolve the 12 expected peaks in the P-31 spectrum of a-TCP compared to the low-purity STO that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon (Si-29) MAS NMR was also performed on both Si-TCP samples which revealed Q(0) species of Si with additional Si Q(1)/Q(2) species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q(4) Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by P-31 MAS NMR which showed no significant line broadening other than that associated with the emergence of beta-TCP which was only realised with the reagent-grade sample STO. This study provides an insight into the structural effects of Si-substitution in alpha-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2013.11.014

Novel Fluoro-carbon Functional Monomer for Dental Bonding Reviewed

K. Yoshihara, Y. Yoshida, S. Hayakawa, N. Nagaoka, S. Kamenoue, T. Okihara, T. Ogawa, M. Nakamura, A. Osaka, B. Van Meerbeek

JOURNAL OF DENTAL RESEARCH 93 ( 2 ) 189 - 194 2014.2

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS INC

Among several functional monomers, 10-methacryloxydecyl dihydrogen phosphate (10-MDP) bonded most effectively to hydroxyapatite (HAp). However, more hydrolysis-resistant functional monomers are needed to improve bond durability. Here, we investigated the adhesive potential of the novel fluoro-carbon functional monomer 6-methacryloxy-2,2,3,3,4,4,5,5-octafluorohexyl dihydrogen phosphate (MF8P; Kuraray Noritake Dental Inc., Tokyo, Japan) by studying its molecular interaction with powder HAp using solid-state nuclear magnetic resonance (H-1 MAS NMR) and with dentin using x-ray diffraction (XRD) and by characterizing its interface ultrastructure at dentin using transmission electron microscopy (TEM). We further determined the dissolution rate of the MF8P_Ca salt, the hydrophobicity of MF8P, and the bond strength of an experimental MF8P-based adhesive to dentin. NMR confirmed chemical adsorption of MF8P onto HAp. XRD and TEM revealed MF8P_Ca salt formation and nano-layering at dentin. The MF8P_Ca salt was as stable as that of 10-MDP; MF8P was as hydrophobic as 10-MDP; a significantly higher bond strength was recorded for MF8P than for 10-MDP. In conclusion, MF8P chemically bonded to HAp. Despite its shorter size, MF8P possesses characteristics similar to those of 10-MDP, most likely to be associated with the strong chemical bond between fluorine and carbon. Since favorable bond strength to dentin was recorded, MF8P can be considered a good candidate functional monomer for bonding.

DOI： 10.1177/0022034513514447

Liquid phase deposited titania coating to enable in vitro apatite formation on Ti6Al4V alloy Reviewed

Satoshi Hayakawa, Yoshitake Masuda, Keigo Okamoto, Yuki Shirosaki, Kazumi Kato, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 25 ( 2 ) 375 - 381 2014.2

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

A recently developed "GRAPE(A (R)) technology" provides titanium or titanium alloy implants with spontaneous apatite-forming ability in vitro, which requires properly designed gaps and optimum heat treatment in air. In this study, titanium alloy and commercially pure (cp) titanium substrates were thermally oxidized in air before aligning pairs of specimens in the GRAPE(A (R)) set-up, i.e., titanium alloy and cp titanium substrates were aligned parallel to each other with optimum gap width (spatial design). A liquid phase deposition (LPD) technique was employed for titania coatings on titanium alloy substrate. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 A degrees C) for 7 days to confirm the in vitro apatite formation on the substrates under the specific spatial design. Anatase-type titania coatings fabricated by using LPD technique led to the deposition of apatite particles within 7 days and showed apatite X-ray diffraction. On the other hand, thermally oxidized titanium alloy substrate in air and non-treated specimens did not show any apatite X-ray diffraction. These results indicated that the heterogeneous nucleation of apatite induced on anatase-type titania coating prepared by LPD technique when it was aligned parallel to thermally oxidized cp titanium substrate with optimum gap width.

DOI： 10.1007/s10856-013-5078-z

Biomedical applications of sol-gel nanocomposites Reviewed

Song Chen, Satoshi Hayakawa, Yuki Shirosaki, Nobutaka Hanagata, Akiyoshi Osaka

Sol-Gel Nanocomposites 167 - 190 2014.1

Language：English Publishing type：Part of collection (book) Publisher：Springer New York

This chapter introduces nanocomposites of silica, titania, calcium phosphates, biologically active glasses, and their polymer-modified derivatives with meso- and macro-porous, nanotubular, or hollow nanoparticle-type structures that have been prepared via the sol-gel routes. Their applications for delivering drugs and DNAs, tissue-materials interactions, and tissue regeneration are briefly described.

DOI： 10.1007/978-1-4939-1209-4_7

The role of the chemical composition of monetite on the synthesis and properties of alpha-tricalcium phosphate Reviewed

Jo Duncan, James F. MacDonald, John V. Hanna, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka, Janet M. S. Skakle, Iain R. Gibson

MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS 34 123 - 129 2014.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

There has been a resurgence of interest in alpha-tricalcium phosphate (alpha-TCP), with use in cements, polymer composites and in bi- and tri-phasic calcium phosphate bone grafts. The simplest and most established method for preparing alpha-TCP is the solid state reaction of monetite (CaHPO4) and calcium carbonate at high temperatures, followed by quenching.
In this study, the effect of the chemical composition of reagents used in the synthesis of alpha-TCP on the local structure of the final product is reported and findings previously reported pertaining to the phase composition and stability are also corroborated. Chemical impurities in the monetite reagents were identified and could be correlated to the calcium phosphate products formed; magnesium impurities favoured the formation of beta-TCP, whereas single phase alpha-TCP was favoured when magnesium levels were low. Monetite synthesised in-house exhibited a high level of chemical purity; when this source was used to produce an alpha-TCP sample, the alpha-polymorph could be obtained by both quenching and by cooling to room temperature in the furnace at rates between 1 and 10 degrees C/min, thereby simplifying the synthesis process. It was only when impurities were minimised that the 12 phosphorus environments in the alpha-TCP structure could be resolved by P-31 nuclear magnetic resonance; samples containing chemical impurity showed differing degrees of line-broadening. Reagent purity should therefore be considered a priority when synthesising/characterising the alpha-polymorph of TCP. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2013.08.038

Challenges for Nerve Repair Using Chitosan-Siloxane Hybrid Porous Scaffolds Reviewed

Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka, Maria A. Lopes, Jose D. Santos, Stefano Geuna, Ana C. Mauricio

BIOMED RESEARCH INTERNATIONAL 2014 7 2014

Language：English Publisher：HINDAWI PUBLISHING CORPORATION

The treatment of peripheral nerve injuries remains one of the greatest challenges of neurosurgery, as functional recover is rarely satisfactory in these patients. Recently, biodegradable nerve guides have shown great potential for enhancing nerve regeneration. A major advantage of these nerve guides is that no foreign material remains after the device has fulfilled its task, which spares a second surgical intervention. Recently, we studied peripheral nerve regeneration using chitosan-gamma-glycidoxypropyltrimethoxysilane (chitosan-GPTMS) porous hybrid membranes. In our studies, these porous membranes significantly improved nerve fiber regeneration and functional recovery in rat models of axonotmetic and neurotmetic sciatic nerve injuries. In particular, the number of regenerated myelinated nerve fibers and myelin thickness were significantly higher in rat treated with chitosan porous hybrid membranes, whether or not they were used in combination with mesenchymal stem cells isolated from the Wharton's jelly of the umbilical cord. In this review, we describe our findings on the use of chitosan-GPTMS hybrids for nerve regeneration.

DOI： 10.1155/2014/153808

Sol-Gel-Derived Silicate Nano-Hybrids for Biomedical Applications Reviewed

Kanji Tsuru, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

BIOLOGICAL & PHARMACEUTICAL BULLETIN 36 ( 11 ) 1683 - 1687 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHARMACEUTICAL SOC JAPAN

Organic-inorganic hybrids of poly(dimethyl siloxane), gelatin, and chitosan with such silanes as tetraethoxysilane and 3-glycidoxytriethoxysilane are derived via the sol-gel routes. Their biomedical applications are discussed from biomimetic deposition of bone-like apatite, cell culture, and in vivo behavior.

DOI： 10.1248/bpb.b13-00526

Preparation of injectable hydroxyapatite/collagen paste using sodium alginate and influence of additives Reviewed

Taira Sato, Akinori Kochi, Yuki Shirosaki, Satoshi Hayakawa, Mamoru Aizawa, Akiyoshi Osaka, Masanori Kikuchi

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 121 ( 1417 ) 775 - 781 2013.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Preparation of injectable hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) paste utilizing sodium alginate (Na-Alg) and influence of additives on the paste properties were investigated. The HAp/Col at the HAp and collagen mass ratio of 80:20 synthesized by a simultaneous titration method was pelletized to 100-212 mu m. The HAp/Col powder and that treated with 100mM CaCl2 (Ca-HAp/Col) were used as starting powders. A paste was prepared by mixing of the starting powder and Na-Alg solution at one of several powder/liquid ratios. The paste was directly injected into 100mM CaCl2 solution to confirm setting capability, and examined a viscosity, hardening behavior, compressive strength and decay property. In addition, the paste supplemented with an organic acid or a calcium compound as an additive was also prepared to examine influences of the additive on paste properties. The organic acid was chosen from citric, succinic, malic, lactic and glycolic acids, and the calcium compound was chosen from Ca(OH)(2), Ca(CO)(3), CaSO4 center dot 0.5H(2)O and calcium citrate.
The prepared paste was set by direct injection to 100mM CaCl2 solution. The suitable mixing conditions of the paste were a P/L ratio of 0.6 at the 90:10 mass ratio of Ca-HAp/Col and solution of low viscous Na-Alg. All additives increased the paste viscosity; however, the mechanisms were different between organic acids and calcium compounds. Organic acids rapidly decreased pH to form Alg gel by deposition of Alg. Contrarily, calcium compounds supplied Ca2+ ions to form egg-box structure for gelation of Alg, and the reaction depended on solubility of compound. Additives also increased decaying time but could not realize anti-decay in the present conditions. The results suggested that the HAp/Col injectable paste can be utilized in rapid prototyping materials and might be good candidate for injectable artificial bone with further improvement in anti-decay property. (C)2013 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.121.775

Adhesive interfacial interaction affected by different carbon-chain monomers Reviewed

Kumiko Yoshihara, Yasuhiro Yoshida, Noriyuki Nagaoka, Satoshi Hayakawa, Takumi Okihara, Jan De Munck, Yukinori Maruo, Goro Nishigawa, Shogo Minagi, Akiyoshi Osaka, Bart Van Meerbeek

DENTAL MATERIALS 29 ( 8 ) 888 - 897 2013.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Objectives. The functional monomer 10-methacryloxydecyl dihydrogen phosphate (10-MDP), recently used in more self-etch adhesives, chemically bonds to hydroxyapatite (HAp) and thus tooth tissue. Although the interfacial interaction of the phosphoric-acid functional group of 10-MDP with HAp-based substrates has well been documented, the effect of the long carbon-chain spacer of 10-MDP on the bonding effectiveness is far from understood.
Methods. We investigated three phosphoric-acid monomers, 2-methacryloyloxyethyl dihydrogen phosphate (2-MEP), 6-methacryloyloxyhexyl dihydrogen phosphate (6-MHP) and 10-MDP, that only differed for the length of the carbon chain, on their chemical interaction potential with HAp and dentin, this correlatively using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial 6-MHP and 10-MDP containing adhesives were investigated as well.
Results. XRD revealed that on HAp only 10-MDP produced monomer-calcium salts in the form of 'nano-layering', while on dentin all monomers produced 'nano-layering', but with a varying intensity in the order of 10-MDP > 6-MHP > 2-MEP. TEM confirmed that 10-MDP formed the thickest hybrid and adhesive layer. XRD and TEM revealed 'nano-layering' for all commercial adhesives on dentin, though less intensively for the 6-MHP containing adhesive than for the 10-MDP ones.
Significance. It is concluded that not only the phosphoric-acid group but also the spacer group, and its length, affect the chemical interaction potential with HAp and dentin. In addition, the relatively strong 'etching'' effect of 10-MDP forms more stable monomer-Ca salts, or 'nano-layering', than the two shorter carbon-chain monomers tested, thereby explaining, at least in part, the better bond durability documented with 10-MDP containing adhesives. (c) 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2013.05.006

Aluminium-free glass polyalkenoate cements: ion release and in vitro antibacterial efficacy Reviewed

A. W. Wren, J. P. Hansen, S. Hayakawa, M. R. Towler

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 24 ( 5 ) 1167 - 1178 2013.5

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Glass polyalkenoate cements (GPCs) have exhibited potential as bone cements. This study investigates the effect of substituting TiO2 for SiO2 in the glass phase and the subsequent effect on cement rheology, mechanical properties, ion release and antibacterial properties. Glass characterization revealed a reduction in glass transition temperature (T (g) ) from 685 to 669 A degrees C with the addition of 6 mol % TiO2 (AT-2). Magic angle spinning nuclear magnetic resonance (MAS-NMR) revealed a shift from -81 ppm to -76pmm when comparing a Control glass to AT-2, indicating de-polymerization of the Si network. The incorporation of TiO2 also increased the working time (T (w) ) from 19 to 61 s and setting time (T (s) ) from 70 to 427 s. The maximum compressive strength (sigma (c) ) increased from 64 to 85 MPa. Ion release studies determined that the addition of Ti to the glass reduced the release of zinc, calcium and strontium ions, with low concentrations of titanium being released. Antibacterial testing in E. coli resulted in greater bactericidal effects when tested in aqueous broth for both titanium containing cements.

DOI： 10.1007/s10856-013-4880-y

Nucleation and growth of apatite on an anatase layer irradiated with UV light under different environmental conditions Reviewed

Keita Uetsuki, Shinsuke Nakai, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A 101 ( 3 ) 712 - 719 2013.3

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Implant surfaces must sometimes be modified to form strong bonds to host tissues. The method of depositing an anatase layer on chemically pure titanium by chemical oxidation with H2O2 and subsequent calcination (CHT) is known to deposit apatite under physiological conditions; it thus exhibits bone-bonding ability. UV irradiation should affect the bonding ability because the CHT anatase layer would experience certain chemical modifications, such as a decrease or an increase in the number of TiOH and TiO(H)Ti sites; these sites are considered active sites for apatite nucleation. When in vitro apatite deposition was examined, using Kokubo's simulated body fluid, UV irradiation in air reduced the apatite-forming ability of the CHT anatase layer, and UV irradiation on the samples in water enhanced the ability. These results were correlated to changes in the Ti?OH and TiO(H)Ti sites, as determined by O 1s X-ray photoelectron spectroscopy. Analysis of the number and size of the semi-spherical apatite particles and their surface coverage led to a model: proper assembly of the Ti?OH and TiO(H)Ti sites should only give rise to the induction of apatite nucleation, analogous to topotaxy effects.(C) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 712-719, 2013.

DOI： 10.1002/jbm.a.34370

Revisiting structure of silica gels from water glass: an H-1 and Si-29 MAS and CP-MAS NMR study Reviewed

Jie Li, Satoshi Hayakawa, Yuki Shirosaki, Akiyoshi Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 65 ( 2 ) 135 - 142 2013.2

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

The silica gels, derived from water glass solution with pH adjusted at 3.0 and 9.9, were revisited to investigate their constitution, although water glass has been studied for last tens of decades on gelation. Solid-state nuclear magnetic resonance spectroscopy was applied to the nuclei H-1 and Si-29, by the use of magic angle spinning (MAS), H-1 -> Si-29 CP-MAS (CP: cross-polarization), and modern techniques such as 2D HETCOR (two dimensional heteronuclear correlation), and variable-contact time CP techniques. Gelation time (t(gel)) showed U-letter shape dependence on pH. All gels consisted of Q(n) groups (n: 2, 3, and 4), where Q(n) stands for a silicate unite [(O-1/2)(n)Si (-O-)(4-n)] (n: 0-4). The analysis of the H-1 -> Si-29 CP kinetics and H-1-Si-29 HETCOR spectra elucidated the presence of four kinds of H-1 nuclei, i.e., those giving a peak at 6.9 ppm in chemical shift delta: H-1-OSi hydrogen bonded to H2O molecules; one at 4.3 ppm: H-1 of adsorbed water molecules, hydrogen-bonded to the silanol groups; one at 1.7 ppm: H-1-OSi confined in the gel lattice, including that forming aggregations like Si-O-H/O-Na-Si; and one at 4.2 ppm: H-1 of water molecules on the outermost hydration layer.

DOI： 10.1007/s10971-012-2917-1

Preparation of inorganic-organic hybrid membrane for peripheral nerve reconstruction Reviewed

Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka, Maria A. Lopes, José D. Santos, Ana C. Maurîcio, Stefano Geuna

9th IMAPS/ACerS International Conference and Exhibition on Ceramic Interconnect and Ceramic Microsystems Technologies, CICMT 2013 173 - 176 2013.1

The treatment of peripheral nerve injuries is still one of the most challenging tasks in neurosurgery, as functional recovery is rarely satisfactory in these patients. The concept behind the use of biodegradable nerve guides is that no foreign material should be left in place after the device has fulfilled its task, so as to spare a second surgical intervention. In a previous study, flexible and biodegradable chitosan-3-glycidoxypropyltrimethoxysilane (GPTMS) hybrid membranes exhibited better cytocompatibility in terms of osteoblastic cells than chitosan membrane. Porous chitosan hybrid membranes, derived by freeze-drying the hybrid gels, showed that the cells were attached and proliferated both on the surface and into pores. In this study, the porous chitosan-silicate hybrid membranes with non-differentiated human mesenchymal stem cells isolated from Wharton's jelly of umbilical cord were used to reconstruct the crushed peripheral nerve. Axonotmesis lesion of 3 mm was enwrapped with the hybrid membranes with or without a monolayer of non-differentiated human mesenchymal stem cells. Motor and sensory functional recovery was evaluated throughout a healing period of 12 weeks. The combination of hybrid membranes and human MSCs infiltration showed a slightly better recovery than the untreated control (the just crushed nerve). On the other hand, the hybrid membrane alone promoted the crushed peripheral nerve reconstruction. It is expected that the porous chitosan hybrid membranes is candidate for the clinical tool in peripheral nerve reconstructive surgery.

Heterogeneous structure and in vitro degradation behavior of wet-chemically derived nanocrystalline silicon-containing hydroxyapatite particles

Satoshi Hayakawa, Tomoko Kanaya, Kanji Tsuru, Yuki Shirosaki, Akiyoshi Osaka, Eiji Fujii, Koji Kawabata, Georgiana Gasqueres, Christian Bonhomme, Florence Babonneau, Christian Jaeger, Hans-Joachim Kleebe

ACTA BIOMATERIALIA 9 ( 1 ) 4856 - 4867 2013.1

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Nanocrystalline hydroxyapatite (HAp) and silicon-containing hydroxyapatite (SiHAp) particles were synthesized by a wet-chemical procedure and their heterogeneous structures involving a disordered phase were analyzed in detail by X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The effects of heterogeneous structure on in vitro biodegradability and the biologically active Ca(II)- and Si(IV)-releasing property of SiHAp particles were discussed. The Si-29 NMR analysis revealed that the Si(IV) was incorporated in the HAp lattice in the form of Q(0) (SiO44- or HSiO43-) species, accompanied by the formation of condensed silicate units outside the HAp lattice structure, where the fraction and amount of Q(0) species in the HAp lattice depends on the Si content. The P-31 and H-1 NMR results agreed well with the XRD, TEM and FTIR results. NMR quantitative analysis results were explained by using a core-shell model assuming a simplified hexagonal shape of HAp covered with a disordered layer, where Si(IV) in Q(0) was incorporated in the HAp lattice and a disordered phase consisted of hydrated calcium phosphates involving polymeric silicate species and carbonate anions. With the increase in the Si content in the HAp lattice, the in vitro degradation rate of the SiHAps increased, while their crystallite size stayed nearly unchanged. The biologically active Ca(II)- and Si(IV)-releasing ability of the SiHAps was remarkably enhanced at the initial stage of reactions by an increase in the amount of Si(IV) incorporated in the HAP lattice but also by an increase of the amount of polymeric silicate species incorporated in the disordered phase. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2012.08.024

HEMA Inhibits Interfacial Nano-layering of the Functional Monomer MDP Reviewed

Y. Yoshida, K. Yoshihara, S. Hayakawa, N. Nagaoka, T. Okihara, T. Matsumoto, S. Minagi, A. Osaka, K. Van Landuyt, B. Van Meerbeek

JOURNAL OF DENTAL RESEARCH 91 ( 11 ) 1060 - 1065 2012.11

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS INC

Previous research showed that the functional monomer 10-methacryloxydecyl dihydrogen phosphate (MDP) ionically bonds to hydroxyapatite (HAp) and forms a nano-layered structure at the interface with HAp-based substrates. Such hydrophobic nano-layering is considered to contribute to the long-term durability of the bond to tooth tissue. However, dental adhesives are complex mixtures usually containing different monomers. This study investigated the effect of the monomer 2-hydroxyethylmethacrylate (HEMA) on the chemical interaction of MDP with HAp by x-ray diffraction (XRD), nuclear magnetic resonance (NMR), and quartz crystal microbalance (QCM). We examined the chemical interaction of 5 experimental MDP solutions with increasing concentrations of HEMA. XRD revealed that addition of HEMA inhibits nano-layering at the interface, while NMR confirmed that MDP remained adsorbed onto the HAp surface. QCM confirmed this adsorption of MDP to HAp, as well as revealed that the demineralization rate of HAp by MDP was reduced by HEMA. It was concluded that even though the adsorption of MDP to HAp was not hindered, addition of HEMA inhibited interfacial nano-layering. Potential consequences with regard to bond durability necessitate further research.

DOI： 10.1177/0022034512460396

Electrospun poly(vinyl alcohol) as a template of silica hollow and solid micro-fibrous mats Reviewed

Yuki Shirosaki, Hiroki Yoshihara, Song Chen, Mark Blevins, Yuri Nakamura, Nobutaka Hanagata, Satoshi Hayakawa, Artemis Stamboulis, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 120 ( 1407 ) 520 - 524 2012.11

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Silica fiber mats were fabricated by soaking electro-spun poly(vinyl alcohol) fibril mat in NH4OH-catalyzed (Stober type) colloidal silica sol and silica oligomer solution from HCl-catalysis of the system tetraethoxysilane, ethanol, and water, followed by appropriate heat treatments. The silica fibrils from the Stober silica sol were hollow nano-tubes (NT) consisting of nano-sized silica particles, while the silica nanofibers (NF) from the acid-catalyzed sol were solid with minimal porosity. A model was proposed for the NF and NT formation processes. (C)2012 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.120.520

Use of hybrid chitosan membranes and human mesenchymal stem cells from the Wharton jelly of umbilical cord for promoting nerve regeneration in an axonotmesis rat model Reviewed

Andrea Gaertner, Tiago Pereira, Maria Joao Simoes, Paulo A. S. Armada-da-Silva, Miguel L. Franca, Rosa Sousa, Simone Bompasso, Stefania Raimondo, Yuki Shirosaki, Yuri Nakamura, Satoshi Hayakawa, Akiyoshi Osakah, Beatriz Porto, Ana Lucia Luis, Artur S. P. Varejao, Ana Colette Mauricio

NEURAL REGENERATION RESEARCH 7 ( 29 ) 2247 - 2258 2012.10

Language：English Publishing type：Research paper (scientific journal) Publisher：SHENYANG EDITORIAL DEPT NEURAL REGENERATION RES

Many studies have been dedicated to the development of scaffolds for improving post-traumatic nerve regeneration. The goal of this study was to assess the effect on nerve regeneration, associating a hybrid chitosan membrane with non-differentiated human mesenchymal stem cells isolated from Wharton's jelly of umbilical cord, in peripheral nerve reconstruction after crush injury. Chromosome analysis on human mesenchymal stem cell line from Wharton's jelly was carried out and no structural alterations were found in metaphase. Chitosan membranes were previously tested in vitro, to assess their ability in supporting human mesenchymal stem cell survival, expansion, and differentiation. For the in vivo testing, Sasco Sprague adult rats were divided in 4 groups of 6 or 7 animals each: Group 1, sciatic axonotmesis injury without any other intervention (Group 1-Crush); Group 2, the axonotmesis lesion of 3 mm was infiltrated with a suspension of 1 250-1 500 human mesenchymal stem cells (total volume of 50 mu L) (Group 2-CrushCell); Group 3, axonotmesis lesion of 3 mm was enwrapped with a chitosan type III membrane covered with a monolayer of non-differentiated human mesenchymal stem cells (Group 3-CrushChitIIICell) and Group 4, axonotmesis lesion of 3 mm was enwrapped with a chitosan type III membrane (Group 4-CrushChitIII). Motor and sensory functional recovery was evaluated throughout a healing period of 12 weeks using sciatic functional index, static sciatic index, extensor postural thrust, and withdrawal reflex latency. Stereological analysis was carried out on regenerated nerve fibers. Results showed that infiltration of human mesenchymal stem cells, or the combination of chitosan membrane enwrapment and human mesenchymal stem cell enrichment after nerve crush injury provide a slight advantage to post-traumatic nerve regeneration. Results obtained with chitosan type III membrane alone confirmed that they significantly improve post-traumatic axonal regrowth and may represent a very promising clinical tool in peripheral nerve reconstructive surgery. Yet, umbilical cord human mesenchymal stem cells, that can be expanded in culture and induced to form several different types of cells, may prove, in future experiments, to be a new source of cells for cell therapy, including targets such as peripheral nerve and muscle.

DOI： 10.3969/j.issn.1673-5374.2012.29.002

Sol-gel preparation of apatite-coated silica macrospheres from water glass and their adsorption of bovine serum albumin and lysozyme Reviewed

Jie Li, Yuki Shirosaki, Satoshi Hayakawa, Artemis Stamboulis, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 120 ( 1405 ) 355 - 361 2012.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Silica gel macrospheres were prepared from water glass as the silica source. The water glass solution was mixed with sodium alginate solution and added dropwisely to 1 M CaCl2 solution to form macrospheres with similar to 4 and 2.6 mm in diameter. Those SiO2 macrospheres were soaked in 1:1 (volume) mixture of ethanol and 0.1 M Na2HPO4 to deposit hydroxyapatite layer (HAp-SiO2 macrospheres). Bovine serum albumin (BSA) and egg lysozyme (LYZ) were adsorbed those SiO2 and HAp-SiO2 macrospheres. The amount of proteins adsorbed was well correlated to the Langmuir-type adsorption equation. The electrostatic interaction was predominant between the macrosphere surface and the protein molecules. Protein molecular entrapment in the mesopores (525 nm) was also probable for the SiO2 macrospheres but not applicable to the HAp-SiO2 ones without the mesopores. From consideration that protein molecule has a few groups with negative or positive partial charges, a multi-layer adsorption model was proposed. (c) 2012 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.120.355

Characterization of hybrid composite membrane based polymer/precursor/SiO2 Reviewed

Uma Thanganathan, Yuta Nishina, Kunio Kimura, Satoshi Hayakawa, Rambabu Bobba

MATERIALS LETTERS 81 88 - 91 2012.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

New class of hybrid composite was synthesized via sol-gel process with the combination of poly(vinyl alcohol) (PVA), TEOS, 3-glycidyloxypropyltrimethoxysilane (GPTMS) reacted with the cross-linking agent glutaraldehyde. The composites demonstrated a maximum high proton conductivity of 1.7 x 10(-2) S cm(-1) at 140 degrees C and a relative humidity of 50% RH. The swelling ratio was calculated in dry and wet conditions, and the composites were found capable of swelling. The structural formation of the composites was studied by techniques such as FTIR, TGA and impedance spectroscopy, and it was concluded that these PVA-SiO2/GPTMS/GA composite membranes exhibited excellent thermal, mechanical and conductivity properties. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2012.04.023

Self-assembled Nano-layering at the Adhesive Interface Reviewed

Y. Yoshida, K. Yoshihara, N. Nagaoka, S. Hayakawa, Y. Torii, T. Ogawa, A. Osaka, B. Van Meerbeek

JOURNAL OF DENTAL RESEARCH 91 ( 4 ) 376 - 381 2012.4

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS INC

According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled 'nano-layering'. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

DOI： 10.1177/0022034512437375

BMP-2-loaded silica nanotube fibrous meshes for bone generation Reviewed

Song Chen, Xuetao Shi, Hiromi Morita, Jie Li, Nobuhiro Ogawa, Toshiyuki Ikoma, Satoshi Hayakawa, Yuki Shirosaki, Akiyoshi Osaka, Nobutaka Hanagata

SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 12 ( 6 ) 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：NATL INST MATERIALS SCIENCE

Silica nanotube fibrous meshes were fabricated as multiple functional matrices for both delivering bone morphological protein-2 (BMP-2) and supporting osteoblast attachment and proliferation. The meshes were fabricated via a collagen-templated sol-gel route and consisted of tubular silica with open ends. BMP-2 was loaded to the meshes by soaking in BMP-2 solution. The meshes effectively enabled the attachment and proliferation of osteoblast MC3T3-E1 cells and delivered bioactive BMP-2 to stimulate cell differentiation. These results demonstrate the potential use of the meshes in bone generation applications.

DOI： 10.1088/1468-6996/12/6/065003

Nanolayering of phosphoric acid ester monomer on enamel and dentin Reviewed

Kumiko Yoshihara, Yasuhiro Yoshida, Satoshi Hayakawa, Noriyuki Nagaoka, Masao Irie, Tatsuyuki Ogawa, Kirsten L. Van Landuyt, Akiyoshi Osaka, Kazuomi Suzuki, Shogo Minagi, Bart Van Meerbeek

ACTA BIOMATERIALIA 7 ( 8 ) 3187 - 3195 2011.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Following the "adhesion-decalcification" concept, specific functional monomers possess the capacity to primary chemically interact with hydroxyapatite (HAp). Such ionic bonding with synthetic HAp has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), manifest as self-assembled "nanolayering". In continuation of that basic research this study aimed to explore whether nanolayering also occurs on enamel and dentin when a 10-MDP primer is applied following a common clinical application protocol. Therefore, the interaction of an experimental 10-MDP primer and a control, commercially available, 10-MDP-based primer (Clearfil SE Bond primer (C-SE), Kuraray) with enamel and dentin was characterized by X-ray diffraction (XRD), complemented with transmission electron microscopy interfacial ultrastructural data upon their reaction with enamel and dentin. In addition, XRD was used to study the effect of the concentration of 10-MDP on nanolayering on dentin. Finally, the stability of the nanolayers was determined by measuring the bond strength to enamel and dentin when a photoinitiator was added to the experimental primer or when interfacial polymerization depended solely on the photoinitiator supplied with the subsequently applied adhesive resin. XRD confirmed nanolayering on enamel and dentin, which was significantly greater on dentin than on enamel, and also when the surface was actively rubbed with the primer. Nanolayering was also proportional to the concentration of 10-MDP in the primer. Finally, the experimental primer needed the photoinitiator to obtain a tensile bond strength to dentin comparable with that of the control C-SE primer (which also contains a photoinitiator), but not when bonded to enamel. It is concluded that self-assembled nanolayering occurs on enamel and dentin, even when following a clinically used application protocol. The lower bonding effectiveness of mild self-etch adhesives to enamel should be ascribed in part to a lower chemical reactivity (nanolayering) with enamel HAP. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2011.04.026

Effect of Disordered Structure of Boron-Containing Calcium Phosphates on their In Vitro Biodegradability Reviewed

Sabrina Barheine, Satoshi Hayakawa, Christian Jaeger, Yuki Shirosaki, Akiyoshi Osaka

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 94 ( 8 ) 2656 - 2662 2011.8

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

This study proposes a new guideline for designing biodegradable apatite ceramics. Boron-containing hydroxyapatite (BHAp) particles were prepared by a high-temperature solid-state reaction processing method and were characterized in terms of their chemical composition, apatite lattice defects and in vitro biodegradability. Solid-state nuclear magnetic resonance analysis showed that boron-incorporation into hydroxyapatite (HAp) derived by thermo-chemical reactions between borate and calcium phosphate phases led to disordered phases (BCaP) of a CaO-P2O5-B2O3-OH system covering the crystalline HAp core. X-ray diffraction analysis indicated that the BCaP phase must consist mainly of a crystalline oxyboroapatite (OBAp) phase. An in vitro biodegradability test showed that BHAp degraded quicker than HAp or beta-tricalcium phosphate. The biodegradability of BHAp particles can be controlled by boron incorporation into a HAp lattice leading to the formation of a disordered OBAp phase.

DOI： 10.1111/j.1551-2916.2011.04400.x

Self-etch Monomer-Calcium Salt Deposition on Dentin Reviewed

K. Yoshihara, Y. Yoshida, S. Hayakawa, N. Nagaoka, Y. Torii, A. Osaka, K. Suzuki, S. Minagi, B. Van Meerbeek, K. L. Van Landuyt

JOURNAL OF DENTAL RESEARCH 90 ( 5 ) 602 - 606 2011.5

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS INC

Previous research, in which the bonding effectiveness of the 3 self-etch monomers HAEPA, EAEPA, and MAEPA was determined, showed that MAEPA was most effective. In this study, the molecular interactions of these monomers with hydroxyapatite and dentin were investigated by combining x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. We tested the null hypothesis that the bonding performance of these monomers does not correlate to the formation of monomer-calcium salts and to hydrolytic stability of these monomer-calcium complexes. Monomer/ethanol/water solutions were prepared and applied to synthetic hydroxyapatite and dentin. While HAEPA and EAEPA dissolved dentin considerably and deposited unstable calcium-phosphate salts (DCPD), MAEPA formed hydrolysis-resistant monomer-calcium salts that remained attached to the dentin surface even after being washed. The chemical stability of the monomer-Ca salts was thought to contribute in particular to the bond durability, but this study shows that the formation of stable monomer-calcium salts also enhances the 'immediate' bonding performance of self-etch adhesives.

DOI： 10.1177/0022034510397197

Fabrication of hydroxyapatite with controlled morphology in a micro-reactor Reviewed

Eiji Fujii, Koji Kawabata, Yoshiaki Nakazaki, Yuji Tanizawa, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 ( 1386 ) 116 - 119 2011.2

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A flow-micro-reactor system was employed to fabricate hydroxyapatite (HAp) in order to mimic the interface between calcium and phosphate solutions on a wet chemical procedure. The mixing ratio of calcium nitrate tetrahydrate and diammonium hydrogenphosphate solution was set to the stoichiometric atomic ratio HAp, 1.67, while pH value of the product suspension was varied from 6.4 to 10.0. The product morphology was changed from nano-sheet type to nano-particle type via nano-rod one, while their size was decreased from 100-500 nm to 50 nm. All as-prepared samples, irrespective of pH value of the resultant suspension, consisted of HAp, predominant phase, octacalcium phosphate (OCP), and dicalcium phosphate dihydrate (DCPD) or dicalcium phosphate anhydrate (DCPA). A batch system using the same solutions yielded very similar results, which confirmed that the reactions in this micro-reactor well reproduced a large-scale mixing system. Calcining sample obtained from pH 6.4 suspension for 2 h at lower temperatures (<400 degrees C) lead to decomposition of DCPD, DCPA, and OCP. Trace tricalcium phosphate (TCP) appeared on calcination above 400 degrees C. HAp remained the predominant phase throughout the process. After calcination at 600 degrees C, no other phases than HAp and TCP were present in the product. The analyzed ratio Ca/P (1.38) implied that those crystalline phases were highly Ca-deficient, and that amorphous calcium phosphates were involved in both as-prepared and calcined sample pH 6.4. (C)2011 The Ceramic Society of Japan. All rights reserved

DOI： 10.2109/jcersj2.119.116

GRAPE® Technology:チタン合金に骨組織親和性を付与する微小空間デザインと熱酸化

尾坂明義, 杉野篤史, 都留寛治, 早川聡, 城﨑由紀, 大槻主税, 蔵本孝一

人工臓器 40 ( 1 ) 66 - 69 2011

Preparation of osteocompatible Si(IV)-enriched chitosan-silicate hybrids Reviewed

Yuki Shirosaki, Kanji Tsuru, Hirofumi Moribayashi, Satoshi Hayakawa, Yuri Nakamura, Iain R. Gibson, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 118 ( 1383 ) 989 - 992 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Chitosan-gamma-glycidoxypropyltrimethoxysilane (GPTMS)-tetraethoxysilane (TEOS) hybrid membranes were prepared by the sol-gel method. The effects of Si(IV) released from them on cell proliferation and differentiation were examined in terms of cell metabolic activity and the alkaline phosphatase (ALP) activity of MG63 osteoblastic cells. The amount of Si(IV) released from the hybrid membranes increased with the TEOS content. The released Si(IV) inhibited cell proliferation but promoted cell differentiation. Thus, the osteocompatibility of the chitosan hybrid membranes in the chitosan-GPTMS-TEOS system can be controlled by the amount of Si(IV) released from them when they are applied to cell culture. (C) 2010 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.118.989

Effects of UV-irradiation on in vitro apatite-forming ability of TiO2 layers Reviewed

Keita Uetsuki, Haruki Kaneda, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS 173 ( 1-3 ) 213 - 215 2010.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Titanium and its alloys are employed as artificial joints, bone plates, wires, screws and bone prostheses in orthopedic and dental fields, because of their high corrosion resistance, good mechanical properties, and biocompatibility. Since they cannot directly bond to living bone-tissue through stable chemical interactions, a few surface modification techniques have been proposed for giving materials apatite-forming ability that secures bone-tissue bonding, such as chemical treatment with H2O2 or NaOH, electrochemical oxidation, electrophoretic apatite particle deposition, and UV-irradiation of surface titanium oxide layer. This study examined how the combination of H2O2 chemical treatment and UV-irradiation affected in vitro apatite-formation on TiO2 (anatase phase) layers as UV was irradiated under a few different conditions. TiO2 layer was prepared by the chemical treatment with H2O2 solution and subsequent heat-treatment (CHT). CHT samples were irradiated with UV-light for 1 h in air or in ultra-pure water. They were then soaked in Kokubo's simulated body fluid (SBF; pH 7.4) at 36.5 degrees C for 1 day. Their surface structure and morphology were examined by using a thin film X-ray diffractometer (TF-XRD), and a scanning electron microscope (SEM). The UV-irradiation of CHT in air reduced the number of active sites for apatite nucleation. On the contrary, however, the UV-irradiation in water increased them. These opposite results indicate that environmental factors of the UV-irradiation are important for controlling the in vitro apatite-forming ability of anatase layer. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mseb.2009.11.013

Nano-controlled molecular interaction at adhesive interfaces for hard tissue reconstruction Reviewed

Kumiko Yoshihara, Yasuhiro Yoshida, Noriyuki Nagaoka, Daisuke Fukegawa, Satoshi Hayakawa, Atsushi Mine, Mariko Nakamura, Shogo Minagi, Akiyoshi Osaka, Kazuomi Suzuki, Bart Van Meerbeek

ACTA BIOMATERIALIA 6 ( 9 ) 3573 - 3582 2010.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Although decayed/fractured teeth can be reconstructed minimally invasively and nearly invisibly using adhesive technology, the clinical longevity of dental composite restorations is still too short. Water sorption is thought to be the principal cause of destabilization of the biomaterial-tooth bond. However, the actual mechanisms of interfacial degradation are far from understood. Here we report how nano-controlled molecular interaction at the biomaterial-hard tissue interface can improve bond durability. The use of functional monomers with a strong chemical affinity for the calcium in hydroxyapatite is essential for long-term durability. Correlative X-ray diffraction and solid-state nuclear magnetic resonance disclosed a time-dependent molecular interaction at the interface with stable ionic bond formation of the monomer to hydroxyapatite competing in time with the deposition of less stable calcium phosphate salts. The advanced tooth-biomaterial interaction model gives not only an insight into the mechanisms of bond degradation, but also provides a basis to develop functional monomers for more durable tooth reconstruction. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2010.03.024

Enhancement of apatite-forming ability of parallely aligned Ti-substrates with optimum gaps by autoclaving Reviewed

Yoko Nakao, Atsushi Sugino, Kanji Tsuru, Keita Uetsuki, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 118 ( 1378 ) 483 - 486 2010.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Pure titanium pieces were air-oxidized and autoclaved at 121 degrees C for 20 min before aligning various pairs of specimens in the GRAPE (R) set-up, i.e., two pieces of rectangular substrates were aligned parallel to each other with optimum gap width (spatial design). Then, they were soaked in Kokubo's simulated body fluid (SBF) for 7 days to clarify how the autoclaving is to affect the in vitro apatite-forming ability on the substrates under the specific spatial design. Autoclaved specimens deposited a larger number of apatite particles, and showed stronger apatite X-ray diffraction than the specimen only heated in air. X-ray photoelectron spectroscopy (XPS) analysis indicated that the amount of chemically adsorbed OH and Ti-OH groups on the thermally oxidized titanium specimens increased by autoclaving. These results lead to the conclusion that the increase of Ti-OH groups and OH(s) and H2O groups on the surface enhanced the in vitro apatite-forming ability on spatial design. (C)2010 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.118.483

Morphology and structure of organosilica hybrid particles derived from tetramethoxysilane and vinyltrimethoxysilane via a catalyst-free sol-gel route Reviewed

Song Chen, Akiyoshi Osaka, Satoshi Hayakawa, Yuki Shirosaki, Kanji Tsuru

JOURNAL OF MATERIALS CHEMISTRY 20 ( 35 ) 7337 - 7339 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Organosilica hybrid particles were derived for the first time from a catalyst-free neutral sol-gel system of vinyltrimethoxysilane, tetramethoxysilane, ethanol, and water and consisted of T species (CH(2) = CH-Si(-O-Si)(n)(OH, OCH(3))(3-n), n = 2 and 3) and Q species (Si(-O-Si)(n)(OH, OCH(3))(4-n), n = 2, 3, and 4). After combined with poly(methylmethacrylate) and CaCl(2), they induced deposition of bioactive apatite in the Kokubo's simulated body fluid and are applicable for bone regeneration.

DOI： 10.1039/c0jm01546f

Analysis of gamma-irradiated synthetic bone grafts by Si-29 MAS-NMR spectroscopy, calorimetry and XRD Reviewed

D. Boyd, S. Murphy, M. R. Towler, A. W. Wren, S. Hayakawa

JOURNAL OF NON-CRYSTALLINE SOLIDS 355 ( 45-47 ) 2285 - 2288 2009.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Ca-Sr-Zn-Si glasses have demonstrated excellent biocompatibility both in vitro using the MTT assay with L929 mouse fibroblast cells, and in vivo using healthy and ovariectomized female Wistar rats. However, the biological evaluation of the materials was performed on glass granules that were autoclaved, rather than gamma-irradiated; the sterilisation procedure required prior to implantation of these materials in the human body. Given the fact that when a glass is exposed to ionizing radiation changes in its physical properties can take place, it is imperative to determine whether the structure of such glasses will be altered as a result of exposure to the typical amounts of gamma-irradiation required to sterilise such materials prior to implantation. This paper examines the structure of Na-Ca-Sr-Zn-Si glasses using Si-29 MAS-NMR, XRD and DTA and to evaluate the effect of 30 kGy gamma-irradiation on their structure. The Si-29 MAS-NMR results indicate that the peak maxima for each glass remains between -74 ppm and -79 ppm; a chemical shift for Si-29 associated with Q(1) units in silicate glasses, and that the local environment around the Si-29 isotope remains unaltered as a result of exposure. Additional analysis (DTA and XRD) showed that the onset of the glass transition temperature, T-g (in the range 553 degrees C-619 degrees C depending on composition) typically remains unchanged, as a result of exposure to the ionizing radiation, as do the XRD diffractograms for each glass. Therefore it can be concluded that the use of 30 kGy gamma-irradiation does not effect the local environment of the Si-29 isotope in the glasses, nor does it significantly alter the XRD diffraction patterns or the T-g values for CaO-SrO-NaO-ZnO-SiO2 described in this work. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnoncrysol.2009.07.014

Gelatin-siloxane hybrid scaffolds with vascular endothelial growth factor induces brain tissue regeneration Reviewed

M. Takamiya, H. Zhang, K. Deguchi, K. Tsuru, V. Lukic, T. Yamashita, S. Nagotani, S. Hayakawa, A. Osaka, T. Kamiya, K. Abe

JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM 29 S169 - S170 2009.10

Pore Structure of Hard Carbon Made from Phenolic Resin Studied by Xe-129 NMR Reviewed

Kazuma Gotoh, Takahiro Ueda, Taro Eguchi, Koji Kawabata, Kenji Yamamoto, Yuki Murakami, Satoshi Hayakawa, Hiroyuki Ishida

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 82 ( 10 ) 1232 - 1239 2009.10

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

The pore structure of hard carbon samples made from two kinds of phenolic resins by heating between 1073 and 1473 K was investigated by Xe-129 NMR. The difference of porous structure of hard carbon samples by heat treatment temperature, which was difficult to analyze precisely by general gas adsorption methods, could be evaluated by XeNMR at an equilibrium state of xenon gas adsorption. Carbon samples produced by heating precursors under a 0.1 MPa xenon atmosphere showed stronger NMR signals than carbon heated at reduced pressure, despite their almost identical powder X-ray diffraction (XRD) patterns. Applying this method, the dependence of NMR spectra on heating temperature between 1073 and 1473 K was examined. A carbon sample consisting of smaller particles showed almost constant shift values at about 102 ppm, while the peak of another sample with larger particles shifted between 118 and 82 ppm depending on the heating temperature. Then, almost all entrances of each sample closed above 1273 K. Using NMR with the improved heat-treatment by xenon gas, we evaluated pores in hard carbon that were hard to access from the outer surface of the hard carbon.

DOI： 10.1246/bcsj.82.1232

Sol-Gel Synthesis and Microstructure Analysis of Amino-Modified Hybrid Silica Nanoparticles from Aminopropyltriethoxysilane and Tetraethoxysilane Reviewed

Song Chen, Satoshi Hayakawa, Yuki Shirosaki, Eiji Fujii, Koji Kawabata, Kanji Tsuru, Akiyoshi Osaka

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 92 ( 9 ) 2074 - 2082 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL PUBLISHING, INC

Agglomerated amino-modified silica nanoparticles were prepared from a novel Stober-like precursor system consisting of aminopropyltriethoxysilane (APTES), tetraethoxysilane (TEOS), ethanol, and water where the molar ratio APTES/TEOS was 0, 0.1, 1.0, and 2.0, and the molar ratio H(2)O/-SiOC(2)H(5) was about 20 to 60, or great excess amounts of H(2)O were employed. APTES catalyzed the hydrolysis and condensation of both silanes. (29)Si magic angle spinning nuclear magnetic resonance spectra confirmed that the particles consisted of Q(n) species (Si(OSi)(n)(OH)(4-n); n=2, 3, 4) and T(n) species (NH(2)(CH(2))(3)-Si(OSi)(n)(OH)(3-n); n=2, 3). The APTES content in the precursor solutions controlled the agglomerating spherical particle size and morphology: 0.1 in the ratio APTES/TEOS led to almost independent spheres of 300-400 nm, while the larger ratios 1 and 2 led to similar to 250 and similar to 150 nm spheres, respectively, that were largely agglomerated and some were fused to look like peanut-shells. When soaked in Kokubo's simulated body fluid, those amino-modified particles deposited apatite. The mechanisms of particle formation and apatite deposition were discussed in terms of an intraparticle hydrated layer.

DOI： 10.1111/j.1551-2916.2009.03135.x

Surface, Interface, and Bulk Structure of Borate Containing Apatitic Biomaterials Reviewed

Sabrina Barheine, Satoshi Hayakawa, Akiyoshi Osaka, Christian Jaeger

CHEMISTRY OF MATERIALS 21 ( 14 ) 3102 - 3109 2009.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Nuclear magnetic resonance (NMR) has been used for a detailed investigation of the borate incorporation in apatitic biomaterials prepared by high-temperature solid-state reaction sintering. The NMR data clearly show that crystalline hydroxyapatite (HAp) does exist, but it contains only about 30% of the entire phosphate content of the sample. The main phosphate content of about 70% forms a disordered calcium phosphate phase (BCaP) that accommodates the borate units in two structurally different trigonal BO(3)(3-) groups besides some minor linear BO(2)(-) units. The average chemical composition of BCaP was estimated from the NMR spectra. Furthermore, a structural model of these particles is proposed, where HAp forms the crystalline core of these crystals covered by the disordered BCaP, suggesting that the BCaP phase is responsible for the adhesion properties of organic molecules like proteins and not HAp that is the only significant crystalline phase (XRD). Furthermore, the presence of an interface between HAp and BCaP is discussed based on various NMR experiments, including a triple-resonant (11)B-(31)P cross-polarization edited (31)P NMR spectrum with subsequent (31)P{(1)H} REDOR (Rotational Echo DOuble Resonance) dephasing,

DOI： 10.1021/cm900204q

Preparation of nanometer-scale rod array of hydroxyapatite crystal Reviewed

Satoshi Hayakawa, Yaqi Li, Kanji Tsuru, Akiyoshi Osaka, Eiji Fujii, Koji Kawabata

ACTA BIOMATERIALIA 5 ( 6 ) 2152 - 2160 2009.7

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Fabrication of nano- or micro-structured scaffolds to mimic structural and three-dimensional details of natural bone or teeth has been the subject of much interest, and this study proposes a new strategy for self-assembling one-dimensional hydroxyapatite (HAp) nanorods into organized superstructures. A nanometer-scale rod array of HAp having preferred orientation to the c-axis was successfully prepared simply by soaking calcium-containing silicate glass substrates in Na(2)HPO(4) aqueous solution at 80 degrees C for various periods. Those HAp rods grew perpendicularly to the glass surface, and the crystallites covered the glass surface uniformly, resulting in a "dental enamel-like" rod array structure consisting of "pine-leaf-like" structure units. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2009.02.018

XPS study on potential suppression factors of suppressing in vitro apatite formation on anatase films prepared on various substrates Reviewed

Tetsuya Shozui, Kanji Tsuru, Satoshi Hayakawa, Yuki Shirosaki, Akiyoshi Osaka

SURFACE & COATINGS TECHNOLOGY 203 ( 16 ) 2181 - 2185 2009.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Multilayer anatase films were coated by sol-gel technology on various substrates such as stainless-steel, alumina, and glass, respectively. Their in vitro apatite-forming ability was examined by immersion in Kokubo's simulated body fluid (SBF; pH 7.4, 36.5 degrees C). Although on anatase layer on alkali-free glass apatite was deposited within 7 d, no apatite was found on anatase deposited onto stainless steel, alumina or glass substrates within 7 d to prove they were bioinert. X-ray photoelectron spectroscopy was able to detect chromium, aluminum, or sodium on the surface of the anatase films. This indicated that these ions possibly inhibited the in vitro apatite-forming ability. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2009.02.001

Synthesis of Bioactive HEMA-MPS-CaCl2 Hybrid Gels: Effects of Catalysts in the Sol-Gel Processing on Mechanical Properties and in vitro Hydroxyapatite Formation in a Simulated Body Fluid Reviewed

Tomohiro Uchino, Chikara Ohtsuki, Masanobu Kamitakahara, Toshiki Miyazaki, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF BIOMATERIALS APPLICATIONS 23 ( 6 ) 519 - 532 2009.5

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS LTD

We investigated synthetic conditions for the fabrication of bioactive hybrid gels from monomers of 2-hydroxyethylmethacrylate ( HEMA) and 3-methacryloxypropyltrimethoxysilane (MPS) in combination with CaCl2, at a starting molar ratio of HEMA: MPS: CaCl2 of 9:1:1. Hydroxyapatite formation, essential to show bone bonding, was observed on the HEMA-MPS-CaCl2 hybrid gels with the added catalysts NH3 or HCl with a molar ratio to MPS of 0.1, but not on the hybrid gel with HCl at a molar ratio to MPS of 1. The mechanical properties of the gels were dependent on the catalysts, which may affect the microstructures that develop during sol-gel processing.

DOI： 10.1177/0885328208094262

Induced deposition of bone-like hydroxyapatite on thermally oxidized titanium substrates using a spatial gap in a solution that mimics a body fluid Reviewed

Atsushi Sugino, Kanji Tsuru, Satoshi Hayakawa, Koichi Kikuta, Giichiro Kawachi, Akiyoshi Osaka, Chikara Ohtsuki

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 117 ( 1364 ) 515 - 520 2009.4

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

We report on the effect of using a spatial gap on heterogeneous nucleation on the surface of thermally oxidized titanium substrates. Induction of heterogeneous nucleation of bone-like hydroxyapatite (BHAp) was evaluated in the spatial gaps between substrates that were thermally oxidized at temperatures of 100-800 degrees C on exposure to a simulated body fluid (SBF). After soaking in a SBF for 7 d, BHAp spontaneously deposited inside the gap on the surface of samples that were thermally oxidized at temperatures above 400 degrees C, but not on samples that were thermally oxidized at temperatures of 300 degrees C or less. Among the substrates studied, BHAp particles were most readily deposited inside the gap on the surface of the samples that were thermally oxidized at 400 degrees C after soaking in an SBF. A smaller gap led to a higher number of BHAp particles being deposited on the surface of the samples that were thermally oxidized at 400 or 500 degrees C. Our results suggest that the formation of BHAp in a SBF is dependent on the temperature during thermal oxidization, and also on the spatial gap between the samples. The ease of formation of BHAp on thermally oxidized titanium increases with increasing thickness of the rutile phase and the number of Ti-OH groups, which are produced during the thermal oxidization process. In addition to the surface structure of the substrates, the spatial gap is regarded as an important parameter for enhancing the deposition of BHAp. Since the formation of BHAp allows osteoconduction to occur after implantation in a bony defect, it is possible to design titanium-based implants with a high biological affinity to bone by processing using an appropriate spatial design of the substrate. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.515

Structure and morphology of aminopropyltriethoxysilane-modified TiO2 nano-particles derived from sol-gel processing of tetraethylorthotitanate Reviewed

Song Chen, Akiyoshi Osaka, Satoshi Hayakawa, Yuki Shirosaki, Eiji Fujii, Koji Kawabata, Kanji Tsuru

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 117 ( 1364 ) 537 - 541 2009.4

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Amino-modified TiO2 particles were derived from precursor mixtures of tetraethylorthotitanate and aminopropyltriethoxysilane (APTES) that both were dissolved in ethanol/water solution. Size, morphology, crystalline structures, and formation mechanism of the particles were discussed in terms of the APTES amount and the pH value in the solution. The addition of APTES resulted in amorphous amino-modified TiO2 particles. The low crystallinity in the final particles was attributed to the polar amino groups. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.537

Physical, chemical and in vitro biological profile of chitosan hybrid membrane as a function of organosiloxane concentration Reviewed

Yuki Shirosaki, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka, Maria Ascensao Lopes, Jose Domingos Santos, Maria Adelina Costa, Maria Helena Fernandes

ACTA BIOMATERIALIA 5 ( 1 ) 346 - 355 2009.1

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

We attempted to prepare chitosan-silicate hybrid for use in a medical application and evaluated the physico-chemical properties and osteocompatibility of the hybrids as a function of gamma-glycidoxypropyltrimethoxysilane (GPTMS) concentration. Chitosan-silicate hybrids were synthesized using GPTMS as the reagent for cross-linking of the chitosan chains. Fourier transform infrared spectroscopy, (29)Si Cp- MAS NMR spectroscopy and the ninhydrin assay were used to analyze the structures of the hybrids, and stress-strain curves were recorded to estimate their Young's modulus. The swelling ability, contact angle and cytocompatibility of the hybrids were investigated as a function of the GPTMS concentration. A certain fraction of GPTMS in each hybrid was linked at the epoxy group to the amino group of chitosan, which was associated with the change in the methoxysilane group of GPTMS due to hybridization. The cross-linking density was around 80% regardless of the volume of GPTMS. As the content of GPTMS increased, the water uptake decreased and the hydrophilicity of the hybrids increased except when the content exceeded amolar ratio of 1.5, when it caused a decrease. The values of the mechanical parameters assessed indicated that significant stiffening of the hybrids was obtained by the addition of GPTMS. The adhesion and proliferation of the MG63 osteoblast cells cultured on the chitosan-GPTMS hybrid surface were improved compared to those on the chitosan membrane, regardless of the GPTMS concentration. Moreover, human bone marrow osteoblast cells proliferated on the chitosan-GPTMS hybrid surface and formed a fibrillar extracellular matrix with numerous calcium phosphate globular structures, both in the presence and in the absence of dexamethasone. Therefore, the chitosan-GPTMS hybrids are promising candidates for basic materials that can promote bone regeneration because of their controllable composition (chitosan/GPTMS ratio). (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2008.07.022

Effect of spatial design and thermal oxidation on apatite formation on Ti-15Zr-4Ta-4Nb alloy Reviewed

Atsushi Sugino, Chikara Ohtsuki, Kanji Tsuru, Satoshi Hayakawa, Takayoshi Nakano, Yoshimitsu Okazaki, Akiyoshi Osaka

ACTA BIOMATERIALIA 5 ( 1 ) 298 - 304 2009.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Apatite formation on the surface of titanium and its alloys is effective for inducing osteoconductivity when implanted in bony defects. The aim of this study was to investigate the effects of thermal oxidation on apatite formation in macro-grooves on Ti-15Zr-4Ta-4Nb. Thermal oxidation at 500 and 600 degrees C in air led to modification of the Ti-15Zr-4Ta-4Nb surface to rutile phase titanium oxide. Ti-15Zr-4Ta-4Nb thermally oxidized at 500 degrees C in air showed no changes in metallographic structure, but not at 600 degrees C. After soaking in a simulated body fluid for 7 days, the formation of apatite could be observed on the internal surfaces of macro-grooves 500 mu m deep and wide on Ti-15Zr-4Ta-4Nb thermally oxidized at 500 and 600 'C in air. These results indicate the potential for osteoconductivity of Ti-15Zr-4Ta-4Nb without changing its metallographic structure, by fabricating only the macro-grooves, i.e., spatial design, and by performing thermal oxidation at 500 degrees C. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2008.07.014

Microstructure evolution in Stober-type silica nanoparticles and their in vitro apatite deposition Reviewed

Song Chen, Akiyoshi Osaka, Satoshi Hayakawa, Kanji Tsuru, Eiji Fujii, Koji Kawabata

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 48 ( 3 ) 322 - 335 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Prepared via Stober-type sol-gel routes were three types of silica particles of < 1 mu m in size: pure silica, Ca-involving silica, and chitosan/alginate-coated silica with a polymershell-silica core structure. Calcium ions were impregnated in the organic layers of the polymer-coated silica particle. The sol-gel procedure was applied to tetraethoxysilane dissolved in an ethanol/water mixture, while Ca-silica was derived from CaCl(2)-containing ethanol/water solutions. Scanning and transmission electron micrograph analyses indicated that those silica particles consisted of similar to 10 nm primary particles, the Ca-silica particles (similar to 500 nm) were larger than the Ca-free ones (similar to 200 nm) and that their size increased with the Ca concentration in the precursor solutions. From (1)H- and (29)Si- magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra and (29)Si cross-polarization NMR spectra, the mechanism of primary particle agglomeration and degradation of the secondary particles in saline were discussed in terms of the content of H(2)O molecules and > Si-OH as well as hydrogen bonding interactions among them. In addition, the Ca-silica and core-shell silica deposited apatite in Kokubo's simulated body fluid. Thus, the present Ca-silica and polymer-coated silica particles were suggested to be applicable to injectable bone fillers for bone generation.

DOI： 10.1007/s10971-008-1823-z

Novel One-pot Sol-Gel Preparation of Amino-functionalized Silica Nanoparticles Reviewed

Song Chen, Akiyoshi Osaka, Satoshi Hayakawa, Kanji Tsuru, Eiji Fujii, Koji Kawabata

CHEMISTRY LETTERS 37 ( 11 ) 1170 - 1171 2008.11

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Amino-functionalized silica nanoparticles smaller than 200 nm in diameter were directly prepared from precursor mixtures of tetraethoxysilane and aminopropyltriethoxysilane in ethanol/water solutions via a novel one-pot sol-gel procedure.

DOI： 10.1246/cl.2008.1170

Bilirubin adsorption property of sol-gel-derived titania particles for blood purification therapy Reviewed

Takuji Asano, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

ACTA BIOMATERIALIA 4 ( 4 ) 1067 - 1072 2008.7

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Titania (anatase) gel powders were prepared by peptizing commercially available titania sols and heating them at temperatures up to 700 degrees C, as candidates for bilirubin adsorbents for blood purification therapy. Those titania particles were in contact with a protein solution containing bilirubin and bovine serum albumin that mimics the blood of bilirubinemia patients. The amount of free or direct bilirubin in the solution insignificant. Indirect bilirubin or a bilirubin complex with albumin was adsorbed on the anatase powders, the primary particle size of which was as large as or larger than the size of an albumin molecule. The surface charge and surface charge density were only minor factors in controlling the indirect bilirubin adsorption. The present results indicated that the size of primary particles and hydrophobicity were significant for the sol-derived anatase in terms of bilirubin adsorption, and both were controllable by the heating temperature and the time period. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2008.02.024

Novel fabrication of nano-rod array structures on titanium and in vitro cell responses Reviewed

Yongxing Liu, Weihui Chen, Yunzhi Yang, Joo L. Ong, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 19 ( 7 ) 2735 - 2741 2008.7

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Nano-scale rod arrays of titania were fabricated on titanium surface by a glass phase topotaxy growth (GPT) method, which was featured by an interfacial reaction between sodium tetraborate coating and the preheated metallic titanium at elevated temperature. The samples were characterized by thin-film X-ray diffraction (XRD), scanning electron microscope (SEM), profilometer and contact angle measurement. Thin-film XRD analysis indicated that the nano-rod arrays were composed of pure rutile titania phase. SEM images showed that these rutile rods were 100-200 nm wide and 1-2 mu m long. The nano-rod arrays had significantly higher average roughness (P < 0.05) and greater hydrophilicity (P < 0.05) compared to the control. Human embryonic palatal mesenchymal (HEPM) cells were grown to evaluate in vitro cell responses to the nano-rod array structures in terms of cell attachment and proliferation. An equivalent high attachment rate of 94% was observed after 4-h incubation, but a lower proliferation rate was observed on the nano-rod array after 12-day culture compared to the control (P < 0.05).

DOI： 10.1007/s10856-008-3396-3

Gelatin-siloxane hybrid scaffolds with vascular endothelial growth factor induces brain tissue regeneration Reviewed

Hanzhe Zhang, Tatsushi Kamiya, Takeshi Hayashi, Kanji Tsuru, Kentaro Deguchi, Violeta Lukic, Atsushi Tsuchiya, Toru Yamashita, Satoshi Hayakawa, Yoshio Ikeda, Akiyoshi Osaka, Koji Abe

CURRENT NEUROVASCULAR RESEARCH 5 ( 2 ) 112 - 117 2008.5

Language：English Publishing type：Research paper (scientific journal) Publisher：BENTHAM SCIENCE PUBL LTD

In the brain after infarction or trauma, the tissue becomes pannecrotic and forms a cavity. In such situation, a scaffold is necessary to produce new tissue. In this study, we implanted a new porous gelatin-siloxane hybrid derived from gelatin and 3-(glycidoxypropyl) trimethoxysilane (gelatin-GPTMS) scaffolds into a brain defect, and investigated whether it makes a new brain tissue. In addition, vascular endothelial growth factor ( VEGF) was added on gelatin-GPTMS scaffolds and its effect on tissue regeneration was examined. At 30 days after the implantation, the marginal territory of the scaffolds became occupied by newly formed tissue. Immunohistochemical analysis revealed that the new tissue was constituted by endothelial, astroglial and microglial cells, some of which were labeled for bromodeoxyuridine (BrdU). Addition of VEGF promoted numbers of these cells. Thus, combination of gelatin-GPTMS scaffolds and VEGF is preferable for brain regeneration.

DOI： 10.2174/156720208784310204

Revisiting silicate substituted hydroxyapatite by solid-state NMR Reviewed

G. Gasqueres, C. Bonhomme, J. Maquet, F. Babonneau, S. Hayakawa, T. Kanaya, A. Osaka

MAGNETIC RESONANCE IN CHEMISTRY 46 ( 4 ) 342 - 346 2008.4

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS LTD

Silicon-substituted hydroxyapatite (Si-HAp) has shown promising properties such as high-bone remodeling around implants. So far, the techniques used for the structural characterization of the Si-HAp have given indirect evidence of the presence of silicon inside the structure (by X-ray and neutron diffraction). In this paper, we focus on Si-HAp derivatives obtained by a precipitation method (widely described in the literature). We demonstrate here by solid-state NMR spectroscopy that only a fraction of the silicon atoms are incorporated into the HAp lattice in the form of Q(0) (SiO44-) species, for 4.6 wt% Si-HAp. A large amount of silicate units are located outside the HAp structure and correspond to silica-gel units. All results were established through Si-29 MAS, H-1 -> Si-29 CP MAS and T1 rho(H-1) edited H-1 -> Si-29 CP MAS experiments. This last pulse scheme acted as a powerful editing sequence, leading to unambiguous spectroscopic conclusions, concerning the location of the SiO44- moieties. Copyright (C) 2008 John Wiley & Sons, Ltd.

DOI： 10.1002/mrc.2109

Modification of Ti implant surface for cell proliferation and cell alignment Reviewed

Jia Ming Zhao, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A 84A ( 4 ) 988 - 993 2008.3

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-LISS

Surface properties of implants are the keys for ensuring their long-lasting anchorage to the tissue. This study aims to develop a novel implant surface microstructure with high biocompatibility and ability of guided tissue formation. By a photolithography method, gold (Au) grids (1 X 1 mm(2) square lattices, 10 pm in grid-line width) were deposited on titanium substrates. They were oxidized with H2O2 solution to yield titania (anatase) layer, and the Au grid formed channels due to larger molar volume of anatase than Ti. L-Cysteine and type I collagen were then immobilized on them to yield the target substrates, CHT-Au-cys-col. Apatite deposited within 3 days when they were soaked in Kokubo's simulated body fluid, regardless of the protein coating, but not on the bottom of the Au channel. Osteoblast-like MC3T3-E1 cells were cultured on the CHT-Au-cys-col substrates, showing that (1) the cysteine-collagen coating promoted cell attachment and proliferation, and (2) the Au channels were filled with the cells which were aligned along the channel direction and were connected to the neighboring cells as well as attached to the channel wall with cytoplasmic extensions. The results thus ensured filopodial guidance for the substrates. (C) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.31426

Surface topography designed to provide osteoconductivity to titanium after thermal oxidation Reviewed

Atsushi Sugino, Keita Uetsuki, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka, Chikara Ohtsuki

MATERIALS TRANSACTIONS 49 ( 3 ) 428 - 434 2008.3

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS

Hydroxyapatite formation on the surface of materials in the body is an essential condition for demonstrating osteoconduction after implantation in bony defects. This paper reports a technique for providing hydroxyapatite formation properties to titanium metals by using specially designed surface topography followed by thermal oxidation. Two pieces of titanium thermally oxidized at 400 degrees C were set together in a V-shape with varied mouth opening. They showed the formation of hydroxyapatite on both facing surfaces after exposure to a simulated body fluid (SBF), when the gap height was approximately less than 600 mu m. Moreover, pure titanium specimens with macro-grooves less than 1000 pm in depth and 800 mu m in width were able to form hydroxyapatite deposits in SBF within 604.8 ks, after they were thermally oxidized at 400 degrees C for 3.6 ks. Hydroxyapatite also formed on the internal surfaces of macro-grooves made in Ti-15-Zr-4Ta-4Nb within 604.8 ks of soaking in SBF, after the sample was thermally oxidized at 500 degrees C for 3.6 ks, whereas it was not deposited on alloy made of Ti-6Al-4V extra low interstitial processed in the same way. These findings indicate that titanium and its alloys can be conferred with hydroxyapatite-forming ability, i.e. osteoconduction, within a controlled spatial gap and thermal oxidation. We conclude that bioactive titanium substrate showing osteoconduction can be produced by using a specially designed surface topography followed by thermal oxidation at an appropriate temperature.

DOI： 10.2320/matertrans.MBW200711

Synthesis and cytocompatibility of porous chitosan-silicate hybrids for tissue engineering scaffold application Reviewed

Yuki Shirosaki, Tomoyuki Okayama, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

CHEMICAL ENGINEERING JOURNAL 137 ( 1 ) 122 - 128 2008.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Chitosan-silicate hybrids with 3D porous structures were prepared with freeze-drying precursor solutions derived from chitosan and gamma-glycidoxypropyltrimethoxysilane (GPTMS). They were formed easily in any shape, such as sheets, pellets, disks, granules, and even roll-cakes. The pore size was strongly dependent on the freezing temperature: lower freezing temperature resulted smaller pores, about 110 mu m for the hybrids frozen at -20 degrees C, and about 50 mu m for those at -85 degrees C. The pore size was little dependent on the GPTMS content. In contrast, the GPTMS content affected porosity a littlie: similar to 80% for chitosan, and similar to 90% for the GPTMS-containing hybrids. Thus, their porous microstructure was controllable due to the freezing temperature and composition. MG63 osteoblastic cells were cultured up to 7 days on the porous hybrids. The cells adhered on the pore walls, proliferated, and migrated deep into the pore structure. It was thus concluded that the present chitosan-silicate hybrids were promising for tissue engineering scaffold applications. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cej.2007.10.012

Low density lipoprotein adsorption on sol-gel derived alumina for blood purification therapy Reviewed

Takuji Asano, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

BIO-MEDICAL MATERIALS AND ENGINEERING 18 ( 3 ) 161 - 170 2008

Language：English Publishing type：Research paper (scientific journal) Publisher：IOS PRESS

Among the clinical treatments of Familial Hyper cholesterolemia patients to reduce the concentration of low density lipoprotein (LDL), blood purification therapy is most suitable in which a blood-compatible adsorbent is employed. In the present study, alumina powders were prepared via a sol-gel route to develop a LDL-adsorbent Aluminum tri2-propoxide was hydrolyzed and subsequently calcined up to 1200 degrees C. Surface charge density and pore size distribution were measured, and the phases were identified. The alumina calcined above 400 degrees C had excellent blood compatibility in terms of endogenous clotting parameters, i.e., partial thromboplastin time: (PTT), prothrombin time: (PT), and the amount of fibrinogen: (Fib). The amount of LDL-adsorption (Delta W-LDL) increased with the calcining temperature, showing a good linear correlation to surface charge density. The 1200 degrees C sample consisted only of a-alumina, and was greatest in Delta W-LDL. All samples involved pores smaller than 20 nm but not the pores large enough to accommodate LDL molecules (20-25 nm). From those results, it was concluded for the present alumina particles that the surface charge density was the primary factor and that the chemical activity of a-alumina also contributed to the excellent LDL-adsorption for the 1200 degrees C sample, while entrapping LDL in the pores was not an active mechanism.

DOI： 10.3233/BME-2008-0519

Enhancement of in vitro apatite-forming ability of thermally oxidized titanium surfaces by ultraviolet irradiation Reviewed

Tetsuya Shozui, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 116 ( 1352 ) 530 - 535 2008

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Ultraviolet (UV) light was irradiated in air for 1 h on titania (rutile) films prepared by thermal oxidation of titanium substrates from 300°C up to 800°C, coded as HT300UV, HT400UV, HT500UV, HT600UV, HT700UV, and HT800UV, respectively. All samples were then soaked in a simulated body fluid (SBF, Kokubo solution) and their in vitro apatite-forming ability was evaluated. It was found that bone-like apatite particles were deposited on HT500UV, HT600UV, and HT700UV within 7 d whereas that was not the case with others during the same period. Moreover, the apatite particles were deposited more on HT500UV than on the others. Therefore, the ultraviolet light irradiation enhanced the in vitro apatite-forming ability of the thermally oxidized titanium. ©2008 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.116.530

空間デザインによるチタン系医用金属へのアパタイト形成能付与

都留寛治, 杉野篤史, 早川聡, 大槻主税, 尾坂明義

PHOSPHORUS LETTER 61 ( 61 ) 10 - 16 2008

Vascular endothelial growth factor promotes brain tissue regeneration with a novel biomaterial polydimethylsiloxane-tetraethoxysilane Reviewed

HanZhe Zhang, Takeshi Hayashi, Kanji Tsuru, Kentaro Deguchi, Mitsuyuki Nagahara, Satoshi Hayakawa, Makiko Nagai, Tatsushi Kamiya, Akiyoshi Osaka, Koji Abe

Journal of Cerebral Blood Flow and Metabolism Volume 1132 Issue 1 pp. 29-35. 2007.11

Background: Injury of the central nervous system (CNS) of mammals may cause irreparable damage due to the limited regeneration capacity of the tissue. In order for the CNS tissue to regenerate, to supply a scaffold for the newly produced cells to adhere is necessary. Application of biodegradable polymers such as collagen, gelatin, fibrin and alginates has been investigated for organ damage other than the CNS. In this context, we recently produced a novel biomaterial from polydimethylsiloxane (PDMS) and tetraethoxysilane (TEOS). We added the most potent angiogenic factor vascular endothelial growth factor (VEGF) and observed the difference in brain regenerative process in the PDMS-TEOS scaffold. Methods: Male Wistar rats of 12 weeks old were anesthetized and placed in a stereotaxic apparatus. A piece of bone over the right frontal cortex was excised, and 2 x 5 mm defect in the brain was made by cutting and aspiration. The defect was positioned from 1.0 mm anterior to 4.0 mm posterior of the bregma and 2.0 to 4.0 mm lateral to the midline. The depth of the lesion was 2.0 mm from the brain surface. The block of PDMS-TEOS scaffold, with or without VEGF, was placed into the lesion immediately after making the defect. The animals were sacrificed at 30 days after PDMS-TEOS scaffold implantation. For histological analysis of the newly formed tissue, the sections were stained with HE. In order to identify cell types in the newly formed tissue, we performed immunohistochemical analysis for glial fibrillary acidic protein (GFAP), an astrocyte marker, and N-acetylglucosamine oligomer (NAGO), an endothelial cells marker. In order to determine whether the cells in PDMS-TEOS scaffold were under mitosis, we carried out double fluorescent study for cell phenotype markers and Ki67. Result: The PDMS-TEOS scaffold remained at the implanted site for 30 days and kept the integrity of brain shape (Fig. A and B). HE staining showed that a small number of cells infiltrated into the PDMS-TEOS scaffold even without VEGF at 30 days after the implantation, but that addition of VEGF significantly increased the number of infiltrated cells NAGO staining showed only a few positive cells in the PDMS-TEOS scaffold without VEGF, but significant increase of endothelial cells with VEGF was confirmed. Immunohistochemical study for GFAP demonstrated that only a few astrocytes were found in the PDMS-TEOS scaffold without VEGF, which was again significantly increased with VEGF. Double staining with proliferation maker Ki67 demonstrated that VEGF significantly increased newly formed astrocytes and endotheial cells, indicating that addition of VEGF accelerated tissue restoration and angiogenesis. Conclusions: The present study showed that a new porous PDMS-TEOS is a good candidate biomaterial for brain tissue restoration. Endothelial as well as glial cells successfully infiltrated into this biomaterial. Addition of VEGF further promoted new tissue formation.

DOI： 10.1016/j.brainres.2006.09.117

Bilirubin adsorption using titanium oxide particles Reviewed

T. Asano, K. Tsuru, S. Hayakawa, A. Osaka

INTERNATIONAL JOURNAL OF ARTIFICIAL ORGANS 30 ( 8 ) 704 - 704 2007.8

Anatase/rutile dual layer deposition due to hydrolysis of titanium oxysulfate with hydrogen peroxide solution at low temperature Reviewed

Fan Xiao, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE 42 ( 15 ) 6339 - 6346 2007.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Anatase/rutile dual layers were deposited on titanium and polyethylene substrates when they were soaked in TiOSO4/H2O2 solution and aged in hot water: The dense bottom layer predominantly consisted of rutile, while the upper layer consisted of loosely packed aggregation of anatase particles. The titania deposition was the results of compromise among three conflicting processes: (1) hydrolysis of TiOSO4 to yield either soluble titania-H2O2 complexes or titania, (2) dissolution of the titania layer under the presence of H2O2, and (3) corrosive reactions between titanium substrates and H2O2 to yield similar complexes or compounds. The dissolution-deposition equilibrium was found associated with pH of the sulfate solution and changed with soaking time. Thus, proper pH value and soaking time in the treating solution were the two key factors to control the formation of dense titania layers. The resulted titania layers were easily covered with fine apatite particles when soaked in a solution supersaturated with its component ions.

DOI： 10.1007/s10853-006-1220-3

Low-temperature deposition of rutile film on biomaterials substrates and its ability to induce apatite deposition in vitro Reviewed

Jin-Ming Wu, Jin-Fang Liu, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 18 ( 8 ) 1529 - 1536 2007.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Low-temperature deposition of crystalline titania films on intrinsically bioinert materials to induce the bioactivity is of practical interest, not only because it meets the demand of providing organic biomaterials with bioactivity, which cannot tolerate high-temperature thermal treatments, but also because it reserves abundant Ti-OH groups facilitating the apatite deposition. In this paper, rutile films with thickness varied from 0.1 mu m to 1.7 mu m were deposited on commercially available pure titanium substrates from 1.5 M titanium tetrachloride aqueous solution kept at 60 degrees C for 3-60 h. The rutile films grew to give a preferred (101) crystalline plane in the X-ray diffraction pattern. After soaking in a simulated body fluid of the Kokubo solution (SBF) for 2 days, the rutile films with thickness over 0.6 mu m were covered with a layer of apatite. All the films with various thickness induced apatite deposition in SBF after soaking for 5 days. The bioinert polytetrafluoroethylene (PTFE) was also found to exhibit remarkable in vitro bioactivity as to induce apatite deposition from SBF within 2 days, after depositing the rutile film on the surface.

DOI： 10.1007/s10856-006-0115-9

Structural characterization and protein adsorption property of hydroxyapatite particles modified with zinc ions Reviewed

Satoshi Hayakawa, Kanae Ando, Kanji Tsuru, Akiyoshi Osaka, Eiji Fujii, Koji Kawabata, Christian Bonhomme, Florence Babonneau

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 90 ( 2 ) 565 - 569 2007.2

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：BLACKWELL PUBLISHING

Zinc-containing hydroxyapatite particles (Zn/HAp) were prepared by an ion exchange reaction process involving hydroxyapatite (HAp) particles with aqueous solutions containing various amounts of zinc nitrate. The Zn2+ ion was partially substituted for the Ca2+ ion position in the HAp lattice, and hence, the obtained samples had changed little in crystallinity, particle size, and specific surface area. Adsorption of bovine serum albumin (BSA) and beta(2)-microglobulin (beta(2)-MG) in solutions containing both BSA and beta(2)-MG was examined. As the Zn2+ ion content in the apatites increased, the adsorbed amount of BSA was almost constant, whereas that of beta(2)-MG increased.

DOI： 10.1111/j.1551-2916.2006.01396.x

Wet deposition of titania-apatite composite in cotton fibrils Reviewed

Satoshi Hayakawa, Jin-Fang Liu, Kanji Tsuru, Akiyoshi Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 40 ( 2-3 ) 253 - 258 2006.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Titania consisting of rutile and anatase was precipitated on and inside of cotton fibrils when cotton was soaked in an aqueous solution of 30 mM TiOSO4 and 30 mM H2O2 kept at 80 degrees C for 24 h. As the resultant titania-cotton fibrils were soaked in a simulated body fluid (Kokubo solution), apatite was deposited on the fibrils to yield cotton-titania-apatite composites within 1 d. Thus, the present study provided a simple technique to prepare titania-apatite composites and coatings on organic materials at low temperature.

DOI： 10.1007/s10971-006-8759-y

Implantation of a new porous gelatin-siloxane hybrid into a brain lesion as a potential scaffold for tissue regeneration Reviewed

Kentaro Deguchi, Kanji Tsuru, Takeshi Hayashi, Mikiro Takaishi, Mitsuyuki Nagahara, Shoko Nagotani, Yoshihide Sehara, Guang Jin, HanZhe Zhang, Satoshi Hayakawa, Mikio Shoji, Masahiro Miyazaki, Akiyoshi Osaka, Nam-Ho Huh, Koji Abe

JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM 26 ( 10 ) 1263 - 1273 2006.10

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

For brain tissue regeneration, any scaffold for migrated or transplanted stem cells with supportive angiogenesis is important once necrotic brain tissue has formed a cavity after injury such as cerebral ischemia. In this study, a new porous gelatin-siloxane hybrid derived from the integration of gelatin and 3-(glycidoxypropyl) trimethoxysilane was implanted as a three-dimensional scaffold into a defect of the cerebral cortex. The porous hybrid implanted into the lesion remained at the same site for 60 days, kept integrity of the brain shape, and attached well to the surrounding brain tissues. Marginal cavities of the scaffolds were occupied by newly formed tissue in the brain, where newly produced vascular endothelial, astroglial, and microglial cells were found with bromodeoxyuridine double positivity, and the numbers of those cells were dose-dependently increased with the addition of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). Extension of dendrites was also found from the surrounding cerebral cortex to the newly formed tissue, especially with the addition of bFGF and EGF. The present study showed that a new porous gelatinsiloxane hybrid had biocompatibility after implantation into a lesion of the central nervous system, and thus provided a potential scaffold for cell migration, angiogenesis and dendrite elongation with dose-dependent effects of additive bFGF and EGF.

DOI： 10.1038/sj.jcbfm.9600275

Synthesis and structural characterization of silica-hybridized hydroxyapatite with gas adsorption capability Reviewed

Eiji Fujii, Koji Kawabata, Kanae Ando, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 ( 1333 ) 769 - 773 2006.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Silica-hybridized hydroxyapatite powder was prepared from a calcium hydroxide and phosphoric acid together with a tetra-n-butyl orthosilicate as the silica source in order to apply it as a gas adsorbent. According to the X-ray diffraction patterns, all peaks were assigned to the hydroxyapatite. No secondary phases, such as calcium hydroxide and silicon oxides, were observed. Moreover, the transmission electron microscope observations indicated that the crystallite size hardly changed by increasing the silicon oxide content. However, the adsorption areas of nitrogen, water and benzene were remarkably dependent on the silicon oxide content. In this paper, in order to explain the change in the adsorption areas, the lattice structure of the silica-hybridized hydroxyapatite is discussed based on the results obtained by the Si-29 and P-31 magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR).

Novel process of submicron-scale ceramic rod array formation on metallic substrate Reviewed

Kazuya Okamoto, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Ceramic Transactions 195 133 - 138 2006.7

Authorship：Corresponding author

Nano-scale rods of titania and tungsten oxide were fabricated on metallic titanium and tungsten substrates by heat-treatment in vucuo. The surface structure and morphology were characterized by Thin-film X-ray diffraction analysis (TF-XRD) und scanning electron microscopy. The TF-XRD analysis indicated that the thermal treatment in vacuo (6.7 × 10-2 Pa) gave TiO2 (rutile; PDF#21-1276) and WO3 (PDF#20-1324) nano-scale rod arrays. The mechanism of the nano-scale rod array formation was explained by the structure matching due to topotaxy and the crystal growth habit.

Apatite formation on rutile and anatase layers derived by hydrolysis of titanylsulfate in a simulated body fluid Reviewed

JM Zhao, JF Liu, JM Wu, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 ( 1327 ) 253 - 258 2006.3

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Titania layers were deposited on titanium substrates in titanylsulfate solutions under varied concentration (0.01 and 0.03M), pH (0.67-1.27) and temperature (60 and 80 degrees C). They were rinsed and subsequently aged in water at 80 degrees C for 3d. The layers consisted of only rutile or rutile with trace anatase, depending on the conditions. The X-ray diffraction intensity indicates that the rutile particles grew preferably in (101) plane, regardless of being aged or not. When aged, the anatase diffraction intensity increased, and anatase newly grew in the layer consisting only of rutile. When soaked in a simulated body fluid (SBF) of the Kokubo recipe, the rinsed layer with only rutile was weakly active to deposit apatite within 5 d, while the other two exhibited no deposition. The aging improved activity. Although anatase is reported in the literature to be more active than rutile, the present study indicates that the rutile layer is more active. Thus, it is concluded that topotaxy or epitaxy would not work well but other issues like the presence of Ti-OH affect apatite deposition.

Selective protein adsorption property and characterization of nano-crystalline zinc-containing hydroxyapatite Reviewed

E Fujii, M Ohkubo, K Tsuru, S Hayakawa, A Osaka, K Kawabata, C Bonhomme, F Babonneau

ACTA BIOMATERIALIA 2 ( 1 ) 69 - 74 2006.1

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Nano-crystalline Zn-containing hydroxyapatite (ZnHAp) was prepared by the wet-chemical method and the selective adsorption of essential proteins was examined, taking bovine serum albumin (BSA) and pathogenic protein such as β2-microglobulin (β2-MG) as model proteins. Transmission electron microscopy observation and X-ray diffraction analysis indicated that the increase of Zn content led to smaller crystallites and their specific surface area of ZnHAps increased with increasing Zn content, accordingly. Furthermore, the amounts of BSA adsorption on ZnHAp particles decreased with increasing Zn content in spite of the increase in the specific surface area. It is thus concluded that nano-crystalline ZnHAps had a highly selective adsorption property with regard to β2-MG. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2005.09.002

Cytocompatibility of silicone elastomer grafted with gamma-methacryloxypropyltrimethoxysilane Reviewed

Y Shirosaki, K Tsuru, S Hayakawa, A Osaka, S Takashima

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 ( 1325 ) 72 - 76 2006.1

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

gamma-Methacryloxypropyltrimethoxysilane (gamma-MPS) was grafted on a silicone elastomer by emulsion polymerization in order to improve cytocompatibility. The wettability of the grafted surface was evaluated with a contact angle toward distilled water. By grafting within 30 min at 60 degrees C, the contact angle was reduced from 110 degrees to about 70 degrees while it remained almost constant for longer grafting. A larger number of osteoblastic cells (MCM-E1) and fibroblast cells (L929) proliferated on the surface modified with gamma-MPS compared with the original silicone surface. After culturing for 7 d, the cells completely covered the grafted surface and even formed a cell layer.

In vivo performance of biodegradable calcium phosphate glass ceramics using the rabbit model: Histological and SEM observation Reviewed

AG Dias, MA Lopes, JD Santos, A Afonso, K Tsuru, A Osaka, S Hayakawa, S Takashima, Y Kurabayashi

JOURNAL OF BIOMATERIALS APPLICATIONS 20 ( 3 ) 253 - 266 2006.1

Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE PUBLICATIONS LTD

Two MK5 (45CaO-45P(2)O(5)-5MgO-5K(2)O, in mol%) and MT13 (45CaO-37P(2)O(5)-5MgO-13TiO(2), in mol%) glasses are prepared in the meta- and pyrophosphate regions and crystallized to obtain MK5B and MT13B, respectively. MK5B was obtained by controlled crystallization, and MT13B by powder sintering. As a result of these heat treatment processes, the crystalline phases precipitated in the glassy matrix are KCa(PO3)(3), beta-Ca(PO3)(2), beta-Ca2P2O7 and Ca4P6O19 phases for MK5B and CaTi4(PO4)(6), TiP2O7, alpha- and beta-Ca2P2O7 phases for MT13B. To assess the in vivo biological behavior of these glass ceramics, a mixed granulometry in the range 250-355 mu m and 355-425 mu m with a ratio of 1/1 was implanted for 2, 4, and 12 weeks in the tibiae of Japanese white rabbits. The results showed that the in vivo behavior was strongly affected by their solubility. All implanted materials, MK5B and MT13B, and beta-tricalcium phosphate (beta-TCP) as control material, showed signs of degradation in vivo. However, the levels of degradation were quite different throughout the implantation periods. The highest degradation was observed for MK5B glass ceramic and the lowest for MT13B with beta-TCP in-between. All implanted materials allow for new bone formation in the bone defect area. At the longest implantation period (12 weeks), the MT13B and beta-TCP materials were almost completely surrounded by new bone tissue, whereas MK5B showed some unfilled spaces. This behavior is discussed in terms of the high degradation observed in previous studies.

DOI： 10.1177/0885328206052466

Apatite formation on rutile and anatase layers derived by hydrolysis of titanylsulfate in a simulated body fluid Reviewed

Jia-Ming Zhao, Jin-Fang Liu, W. U. Jin-Ming, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 114 ( 1327 ) 253 - 258 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Titania layers were deposited on titanium substrates in titanylsulfate solutions under varied concentration (0.01 and 0.03M), pH (0.67-1.27) and temperature (60 and 80°C). They were rinsed and subsequently aged in water at 80°C for 3d. The layers consisted of only rutile or rutile with trace anatase, depending on the conditions. The X-ray diffraction intensity indicates that the rutile particles grew preferably in (101) plane, regardless of being aged or not. When aged, the anatase diffraction intensity increased, and anatase newly grew in the layer consisting only of rutile. When soaked in a simulated body fluid (SBF) of the Kokubo recipe, the rinsed layer with only rutile was weakly active to deposit apatite within 5 d, while the other two exhibited no deposition. The aging improved activity. Although anatase is reported in the literature to be more active than rutile, the present study indicates that the rutile layer is more active. Thus, it is concluded that topotaxy or epitaxy would not work well but other issues like the presence of Ti-OH affect apatite deposition.

DOI： 10.2109/jcersj.114.253

Chemical interaction of phosphoric acid ester with hydroxyapatite Reviewed

D. Fukegawa, S. Hayakawa, Y. Yoshida, K. Suzuki, A. Osaka, B. Van Meerbeek

Journal of Dental Research 85 ( 10 ) 941 - 944 2006

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：SAGE Publications Inc.

Among functional monomers used in contemporary dental adhesives, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) has been found to interact chemically with hydroxyapatite (HAp) most intensively and stably. This effect was thought to be the basis of the superior bonding effectiveness of MDP-based self-etch adhesives to enamel/dentin. To elucidate fully the chemical interaction and reactivity of MDP with HAp, we used 31P CP-MAS NMR spectroscopy and powder x-ray diffraction. In an aqueous ethanol solution, Ca ions were leached from HAp to form, at short term, a MDP-calcium salt (CaMHP2) layered structure on the HAp surface. When MDP was allowed to interact for longer time (&lt
24 hrs), CaHPO4·2H 2O precipitated on top of this MDP-calcium salt layered structure. In conclusion, the intense chemical interaction of MDP with HAp must be ascribed to superficial dissolution of HAp induced by the MDP adsorption and subsequent deposition of MDP-calcium salt with a solubility lower than that of CaHPO 4·2H2O.

DOI： 10.1177/154405910608501014

Synthesis and structural characterization of silica-hybridized hydroxyapatite with gas adsorption capability Reviewed

Eiji Fujii, Koji Kawabata, Kanae Ando, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 114 ( 1333 ) 769 - 773 2006

Language：English Publisher：Ceramic Society of Japan

Silica-hybridized hydroxyapatite powder was prepared from a calcium hydroxide and phosphoric acid together with a tetra-n-butyl orthosilicate as the silica source in order to apply it as a gas adsorbent. According to the X-ray diffraction patterns, all peaks were assigned to the hydroxyapatite. No secondary phases, such as calcium hydroxide and silicon oxides, were observed. Moreover, the transmission electron microscope observations indicated that the crystallite size hardly changed by increasing the silicon oxide content. However, the adsorption areas of nitrogen, water and benzene were remarkably dependent on the silicon oxide content. In this paper, in order to explain the change in the adsorption areas, the lattice structure of the silica-hybridized hydroxyapatite is discussed based on the results obtained by the 29Si and 31P magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR).

DOI： 10.2109/jcersj.114.769

Cytocompatibility of silicone elastomer grafted with γ-Methacryloxypropyltrimethoxysilane Reviewed

Yuki Shirosaki, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka, Seisuke Takashima

Journal of the Ceramic Society of Japan 114 ( 1325 ) 72 - 76 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

γ-Methacryloxypropyltrimethoxysilane (γ-MPS) was grafted on a silicone elastomer by emulsion polymerization in order to improve cytocompatibility. The wettability of the grafted surface was evaluated with a contact angle toward distilled water. By grafting within 30 min at 60°C, the contact angle was reduced from 110° to about 70° while it remained almost constant for longer grafting. A larger number of osteoblastic cells (MC3T3-E1) and fibroblast cells (1929) proliferated on the surface modified with γ-MPS compared with the original silicone surface. After culturing for 7 d, the cells completely covered the grafted surface and even formed a cell layer.

DOI： 10.2109/jcersj.114.72

Synthesis and structural characterization of nanoapatite ceramics powders for biomedical applications

Kanae Ando, Mizuki Ohkubo, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka, Eiji Fujii, Koji Kawabata, Christian Bonhomme, Florence Babonneau

Ceramic Transactions 195 125 - 131 2006

Language：English Publishing type：Research paper (international conference proceedings)

Zn/HAp particles were prepared by soaking hydroxyapatite (HAp), derived through a wet chemical method, into aqueous solutions containing various amounts of zinc nitrate. Obtained samples were characterized by inductively coupled plasma emission spectroscopy, X-ray diffraction (XRD), Brunauer-Emmett-Teller surface area analysis (SA), and transmission electron microscopy. Their zeta potential was also measured. The analyzed Zn content was almost proportional to the content in the aqueous solutions. The Zn 2+ ions were partially replaced the Ca 2+ ions in the apatite, and hence, little change was observed in crystallinity, particle size and SA. Adsorption of bovine serum albumin (BSA) and ß 2-microglobulin (ß 2-MG) in the solutions containing both BSA and ß 2-MG was examined. As the Zn 2+ ion content in the apatites increased, the adsorbed amount of BSA was almost constant, whereas that of ß 2-MG increased. Thus, the Zn incorporation increased the selectivity, and it is suggested that the Zn-substituted site should be the active ones for ß 2-MG adsorption.

In vitro apatite formation on organic polymers modified with a silane coupling reagent Reviewed

Y Shirosaki, M Kubo, S Takashima, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE ROYAL SOCIETY INTERFACE 2 ( 4 ) 335 - 340 2005.9

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOCIETY

gamma-Methacryloxypropyltrimethoxysilane (gamma-MPS) was grafted to high-density polyethylene, polyamide and silicone rubber substrates by the emulsion polymerization procedure in order to provide these organic polymers with in vitro apatite-forming ability. The contact angles towards distilled water of the gamma-MPS-grafted specimens were lower than those of the original organic polymer specimens, indicating that the grafted substrates were more hydrophilic. The in vitro apatite formation in a simulated body fluid (Kokubo solution) was confirmed for several of the gamma-MPS-grafted specimens.

DOI： 10.1098/rsif.2005.0048

ヒドロキシアパタイトとリン酸エステル系機能性モノマーの化学的相互作用

泓川大輔, 吉田靖弘, 鈴木一臣, 早川聡, 尾坂明義, Van Meerbeek Bart

歯科材料・器械 24 ( 5 ) 338 - 338 2005.9

Large-scale preparation of ordered titania nanorods with enhanced photocatalytic activity Reviewed

JM Wu, TW Zhang, YW Zeng, S Hayakawa, K Tsuru, A Osaka

LANGMUIR 21 ( 15 ) 6995 - 7002 2005.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A titania layer with ordered nanostructures is expected to be of high photocatalytic activity due mainly to its high specific surface area. In the present work, large-area films with ordered titania nanorods were deposited on titanium substrates through a solution approach, The nanorods, with the phase composition of a mixture of anatase and rutile, grew on top of a condensed anatase interlayer along mainly the rutile [001]-axis. The photocatalytic activity was evaluated by decomposing rhodamine B in water and compared with the general sol-gel derived titania films and a commercial DP-25 titania coating. It is found that the as-deposited titania nanorods exhibited extremely high initial photocatalytic activity but declined to a poor value after the consumption of beneficial oxidative peroxo complexes coordinated to Ti(IV). A subsequent thermal treatment eliminated such complexes but at the same time improved the crystallinity of the titania nanorods. The photocatalytic activity of the thermally treated titania nanorods was stable and significantly higher than that of the sol-gel derived film and commercial DP-25 coating.

DOI： 10.1021/la0500272

An organic-inorganic hybrid scaffold for the culture of HepG2 cells in a bioreactor Reviewed

K Kataoka, Y Nagao, T Nukui, Akiyama, I, K Tsuru, S Hayakawa, A Osaka, N Huh

BIOMATERIALS 26 ( 15 ) 2509 - 2516 2005.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Much interest has recently been shown in the potential utility of bioartificial liver (BAL) as a bridge support for patients and as a module for experimental purposes. A radial-flow bioreactor (RFB), one of the perfused bed/scaffold-type bioreactors, enables a highly functional three-dimensional culture as BAL. The functional capacity of bioreactors depends not only on their mechanistic structures but also on scaffolds packed in them. In the present study, we examined the possible utility of a new porous organic-inorganic-hybrid scaffold in an RFB. The scaffold was made from tetraethoxysilane (TEOS) and polydimethylsiloxane (PDMS) by a sol-gel method using sieved sucrose particles as a porogen. In the porous TEOS-PDMS hybrid scaffold, human hepatocellular carcinoma cells (HepG2) proliferated actively and formed cell clusters more efficiently than they did in a polyvinyl-alcohol scaffold. When cultivated in PDMS-TEOS, HepG2 cells secreted a similar tothree-fold greater amount of albumin than that secreted in a monolayer culture. For potential application of BAL to pharmacological studies and future clinical use, it is essential to develop a method to propagate liver cells that maintain highly specific functions. The present results indicate that PDMS-TEOS may be a promising scaffold for developing such functional culture methods. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2004.07.012

Preparation of aluminum oxide-hybridized hydroxyapatite powder by the sol-gel method Reviewed

E Fuji, K Kawabata, H Yoshimatsu, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 113 ( 1315 ) 241 - 244 2005.3

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Hydroxyapatite powders (HAp; Ca-10(PO4)(6)(OH)(2)) hybridized with 0-5 mass% Al2O3 were prepared from calcium hydroxide and di-ammonium hydrogenphosphate by a wet chemical synthesis. Ethylacetoacetate Aluminum Diisopropoxide (Al(OC3H7)(2) (C6H9O3)) was used as a source for aluminum oxide. The obtained powders were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) specific surface area measurement, and magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). The X-ray diffraction patterns showed no Al2O3-peaks irrespective of Al2O3 content, suggesting that the Al2O3-hybridized HAp powders were single phase. The Al2O3-hybridized HAp powder had larger specific surface area. According to MAS-NMR analysis, it was considered that the aluminum element existed as aluminum oxide, it was not substituted for the Ca2+, PO43-, or OH- ions.

In vitro cytocompatibility of MG63 cells on chitosan-organosiloxane hybrid membranes Reviewed

Y Shirosaki, K Tsuru, S Hayakawa, A Osaka, MA Lopes, JD Santos, MH Fernandes

BIOMATERIALS 26 ( 5 ) 485 - 493 2005.2

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Chitosan-silicate hybrids were synthesized using gamma-glycidoxypropyltrimethoxysilane (GPSM) as the agent for cross-linking the chitosan chains. CaCl2 was introduced in the hybrids in expectation that it would improve cell adhesion and differentiation of the hybrid surfaces. Fourier-transform infrared (FT-IR) spectroscopy and Si-29 CP-MAS NMR spectroscopy were used to analyze the structures of the hybrids. Cytocompatibility of the hybrids was investigated in terms of proliferation of an osteoblastic cell line, MG63. The adhesion and proliferation of the osteoblastic cells cultured on the Surface of a chitosan-GPSM hybrid without calcium were similar to those on a control Culture plate, and were better than those on a chitosan membrane. The ALP activity of the cells cultured on this hybrid was higher than that on the chitosan membrane. Contrary to expectations, the incorporation of calcium ions into the hybrids did not improve cell attachment and proliferation on their surfaces. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2004.02.056

Formation of Titania submicron-scale rod arrays on titanium substrate and in vitro biocompatibility Reviewed

S Hayakawa, YX Liu, K Okamoto, K Tsuru, A Osaka

Nanoscale Materials Science in Biology and Medicine 845 149 - 154 2005

Authorship：Lead author Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOCIETY

Titania submicron-scale rod arrays were fabricated on metallic titanium (alpha-Ti) surfaces by coating a layer of sodium tetraborale on titanium substrates and subsequent thermal treatment. Thin-film X-ray diffraction analysis indicated that the sodium terraborate gave rutile (TiO2: PDF# 21-1276) submicron-scale rod arrays. The rods in the arrays are parallel to each other in the grain of metallic titanium surface. The titania submicron-scale rod arrays deposited apatite within 7 days after being soaked in a simulated body fluid, indicating that the rod arrays exhibit in vitro bioactivity.

Preparation of aluminum oxide-hybridized hydroxyapatite powder by the sol-gel method Reviewed

Eiji Fujii, Koji Kawabata, Hideyuki Yoshimatsu, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 113 ( 1315 ) 241 - 244 2005

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Hydroxyapatite powders (HAp
Ca10(PO4) 6(OH)2) hybridized with 0-5 mass % Al2O 3 were prepared from calcium hydroxide and di-aminonium hydrogenphosphate by a wet chemical synthesis. Ethylacetoacetate Aluminum Diisopropoxide (Al(OC3H7)2(C6H 9O3)) was used as a source for aluminum oxide. The obtained powders were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) specific surface area measurement, and magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). The X-ray diffraction patterns showed no Al2O3-peaks irrespective of Al2O3 content, suggesting that the Al2O 3-hybridized HAp powders were single phase. The Al2O 3-hybridized HAp powder had larger specific surface area. According to MAS-NMR analysis, it was considered that the aluminum element existed as aluminum oxide, it was not substituted for the Ca2+, PO 4 3-, or OH- ions.

DOI： 10.2109/jcersj.113.241

Mechanism of Apatite Formation on a Sodium Silicate Glass in a Simulated Body Fluid Reviewed

Satoshi Hayakawa, Kanji Tsuru, Chikara Ohtsuki, Akiyoshi Osaka

Journal of the American Ceramic Society 82 ( 8 ) 2155 - 2160 2004.12

Potassium titanate nanorod arrays grown on titanium substrates and their in vitro bioactivity Reviewed

YX Liu, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 112 ( 1312 ) 634 - 640 2004.12

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A novel approach to fabricating highly-oriented, nm-scale potassium titanate K2Ti6O13 rod arrays on titanium substrates was demonstrated. The fabrication process was template-free, and simply involved coating the titanium substrates with pulverized potassium metaborate and its derivatives, and subsequent heating at 700degreesC for 5 h. When the samples were soaked in hot water, the coating layers were readily removed, leaving an array of titanate crystallites on the titanium substrates. Even the slightest change in the composition of the potassium borates resulted in various microstructures, while K2O (.) 1.03B(2)O(3) yielded highly-oriented nanorod arrays of K2Ti6O13. Bioactivity of the as-achieved nanorod arrays was proved by the deposition of apatite in simulated body fluid (SBF: Kokubo solution). When soaked in SBF, the K2Ti6O13 nanorod arrays deposited apatite within one day accompanying the release of potassium ions from the crystallites into SBF and the arrays were covered with apatite layers in three days. Ion exchange between the potassium ions in the crystal and calcium ions in SBF is proposed as the mechanism operative to favor the deposition of apatite.

Preparation of organotitanium molecular layers for biomedical applications Reviewed

T Yoshioka, K Tsuru, S Hayakawa, A Osaka

MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS 24 ( 6-8 ) 901 - 905 2004.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We prepared an organotitanium molecular layer on stainless-steel (SUS316L) substrates, and evaluated its blood compatibility in terms of blood-clotting time and fibrinogen adsorption properties. Titanium methacrylate triisopropoxide (TMT) was used as the organotitanium molecule. The surface was characterized by contact angle measurement toward distilled water and Fourier transform infrared spectroscopy using a reflection absorption method (FT-IRRAS). The obtained organotitanium molecular layer had little effects on the blood-clotting times such as active partial thromboplastin time (PTT) and prothrombin time (PT). Bovine fibrinogen adsorption on the layer was examined from the absorbance of amide I peak in FT-IRRAS spectra. The organotitanium molecular layer reduced the amount of adsorbed fibrinogen compared with stainless-steel. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2004.08.035

Synthesis of bioactive and porous organic-inorganic hybrids for biomedical applications Reviewed

Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of Sol-Gel Science and Technology 32 ( 1-3 ) 201 - 205 2004.12

Language：English Publishing type：Research paper (international conference proceedings)

Bioactivity has been exhibited by a limited range of ceramics since the invention of Bioglass®. Recently, some bioactive polymeric organic-inorganic hybrids were introduced, including not only organically modified silicates (Ormosils) synthesized from polydimethylsiloxane (PDMS) and tetraethoxysilane but also those with gelatin and 3-glycidoxypropyl-tremethoxysilane. Preparation of the bulk and porous hybrids and their polymeric structures analyzed by Si NMR spectroscopy were presented. In vitro bioactivity or apatite deposition in a simulated body fluid of the Kokubo recipe were also described for those hybrids. Freeze-drying techniques introduced porosity (up to 90%) and pores extending in a preferred direction. © 2004 Kluwer Academic Publishers.

DOI： 10.1007/s10971-004-5789-1

Topotaxial nucleation and growth of TiO2 submicron-scale rod arrays on titanium substrates via sodium tetraborate glass coating Reviewed

YX Liu, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 112 ( 1310 ) 567 - 571 2004.10

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A novel approach to fabricate sub-pm scale arrays is demonstrated with the growth of rutile TiO2 on titanium substrates. The fabrication process is template-free, simply involving coating of the titanium substrate with sodium tetraborate glass, Na2O (.) 2B(2)O(3): when the glass coating was removed by dissolution in distilled water at 80degreesC for about 5 h, random or well-ordered submicron-scale rod arrays of rutile were left on the substrate. A glass phase topotaxial (GPT) nucleation and growth mechanism is thought to operate in the crystal growth process.

In vitro bioactive nano-crystalline TiO2 layers grown at glass-coating/titanium interface Reviewed

YX Liu, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 112 ( 1308 ) 452 - 457 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

A new approach is presented to prepare a rutile layer on titanium substrates. According to this approach, pulverized glass, composed of 3CaO - 4B(2)O(3) - 3TiO(2), is first developed on the substrate, heated up to 700 to 850degreesC, and then removed by soaking in hot water. During the heating process, rutile grew at the glass coating-substrate interface to form nano-sized crystallites. The rutile layer induced apatite formation within 3 d when soaked in simulated body fluid of the Kokubo recipe. Such in vitro bioactivity was attributed to many Ti-OH groups on the crystallite surface derived from hydrolysis of bonds at the crysiallite-flux (matrix) interface like (rutile) -Ti-O-B or Ti-O-Ca- (the borate matrix).

Synthesis of blood compatible PDMS-based organic-inorganic hybrid coatings Reviewed

T Yabuta, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 31 ( 1-3 ) 273 - 276 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

PDMS- TiO2 hybrid coating sols were prepared from silanol- terminated polydimethylsiloxane and titanium tetraisopropoxide through sol- gel process. The coating sols were developed on stainless steel substrate with dip- coating technique. The surface structure of the hybrid coating was characterized by Fourier transform infrared ( FT- IR) analysis, contact angle, and surface free energy on the hybrid coating. Blood compatibility was also evaluated in terms of blood clotting time and platelet adhesion. The hybrid coatings have high contact angles and low surface free energies compared to coating- free metal surface. The blood clotting properties were not affected by the hybrid coatings but the platelet adhesion was depressed to less than 1/ 20 as much as that for the coating- free substrate.

DOI： 10.1023/B:JSST.0000048002.65187.3a

Platelet adhesion on titanium oxide gels: effect of surface oxidation Reviewed

S Takemoto, T Yamamoto, K Tsuru, S Hayakawa, A Osaka, S Takashima

BIOMATERIALS 25 ( 17 ) 3485 - 3492 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The correlations between titanium oxide layers on oxidized titanium (Ti) substrates and platelet adhesion were examined. Ti substrates were prepared by three different oxidation methods: the first one was treated with hydrogen peroxide (H2O2) solution, the second one was heated in air at moderate temperatures, and the third one was processed with both H2O2 and heating. The titanium oxide layers formed on the Ti substrates were characterized by wettability, chemical composition, thickness, and crystal phase. The platelet adhesion on these oxide layers was examined and correlated to the characterizations of the surface layers. The number of adhesive platelets seemingly correlated with the contact angle towards distilled water, because the number increased close to 70-80degrees of the contact angle. The effect of surface oxidation on platelet adhesion was examined in detail and it was found that the composition and thickness of the oxide layer influenced platelet adhesion rather than wettability. Thick titanium oxide layers formed on Ti substrates by heating displayed less platelet adhesion than thin oxide layers on untreated Ti substrates. The largest number of adhesive platelets was found on H2O2-oxidized substrates; the substrates found on amorphous titanium oxide contained the Ti-peroxide radical species. The number of platelets, on the other hand, could hardly be observed on Ti substrates treated with H2O2 and subsequently heated above 300 degreesC. The titanium oxide layer on the substrate was thick and we found it to consist of only a few radical species. That is, the effect of heat treatment accelerates the growth of the oxide layer, and decomposes or decreases the number of radical species. Ti substrates with H2O2 and heat treatment above 300 degreesC held the least number of platelets, and were concluded to be the most inhibitory for platelet adhesion. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2003.10.070

Selective protein adsorption and blood compatibility of hydroxy-carbonate apatites. Reviewed International journal

Shinji Takemoto, Yuko Kusudo, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka, Seisuke Takashima

Journal of biomedical materials research. Part A 69 ( 3 ) 544 - 51 2004.6

Language：English Publishing type：Research paper (scientific journal)

We examined the blood compatibility and protein adsorption on hydroxyapatite and hydroxy-carbonate apatite. Those apatites were synthesized under a 0, 5, or 15% CO(2)-containing N(2) atmosphere by a wet-chemical method with a strong ammonia alkali solution of calcium nitrate and diammonium hydrogen phosphate (5:3 in molar ratio) and subsequent calcination in the range of 105-700 degrees C. From infrared (IR) analysis, the carbonate ions substituted both phosphate ions and hydroxyl ions in the hydroxyapatite lattice; the intensities of IR bands assignable to phosphate ions and hydroxyl ions were reduced on calcinations. The specific surface areas of synthesized apatites decreased with increasing calcination temperature. Blood-clotting properties were evaluated in terms of active partial thromboplastin time, prothrombin time, and the amount of fibrinogen for the plasma in contact with the apatites, indicating that all the apatites barely influenced the blood clotting system. The apatites were in contact with a solution containing both bovine serum albumin (BSA) and beta(2)-microglobulin (beta(2)-MG), and the amounts of those proteins adsorbed on them were examined: the amount of absorbed BSA and beta(2)-MG gradually increased with the calcination temperature below 500 degrees C, while it showed a sudden increase when more than 600 degrees C. Hydroxy-carbonate apatite synthesized under a 15% CO(2)-containing N(2) atmosphere and calcined below 400 degrees C had the greatest selectivity in adsorbing beta(2)-MG. Thus, a higher selectivity for beta(2)-MG adsorption was empirically correlated to carbonate ions incorporated in the hydroxyapatite lattice.

Selective protein adsorption and blood compatibility of hydroxy-carbonate apatites Reviewed

S Takemoto, Y Kusudo, K Tsuru, S Hayakawa, A Osaka, S Takashima

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A 69A ( 3 ) 544 - 551 2004.6

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-LISS

We examined the blood compatibility and protein adsorption on hydroxyapatite and hydroxy-carbonate apatite. Those apatites were synthesized under a 0, 5, or 15% CO2-containing N-2 atmosphere by a wet-chemical method with a strong ammonia alkali solution of calcium nitrate and diammonium hydrogen phosphate (5:3 in molar ratio) and subsequent calcination in the range of 105-700degreesC. From infrared (IR) analysis, the carbonate ions substituted both phosphate ions and hydroxyl ions in the hydroxyapatite lattice; the intensities of IR bands assignable to phosphate ions and hydroxyl ions were reduced on calcinations. The specific surface areas of synthesized apatites decreased with increasing calcination temperature. Blood-clotting properties were evaluated in terms of active partial thromboplastin time, prothrombin time, and the amount of fibrinogen for the plasma in contact with the apatites, indicating that all the apatites barely influenced the blood clotting system. The apatites were in contact with a solution containing both bovine serum albumin (BSA) and beta(2)-microglobulin (beta(2)-MG), and the amounts of those proteins adsorbed on them were examined: the amount of absorbed BSA and beta(2)-MG gradually increased with the calcination temperature below 500degreesC, while it showed a sudden increase when more than 600degreesC. Hydroxy-carbonate apatite synthesized under a 15%, CO2-containing N-2 atmosphere and calcined below 400degreesC had the greatest selectivity in adsorbing beta(2)-MG. Thus, a higher selectivity for beta(2)-MG adsorption was empirically correlated to carbonate ions incorporated in the hydroxyapatite lattice. (C) 2004 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.30039

Crystallisation studies of biodegradable CaO-P2O5 glass with MgO and TiO2 for bone regeneration applications Reviewed

AG Dias, K Tsuru, S Hayakawa, MA Lopes, JD Santos, A Osaka

GLASS TECHNOLOGY 45 ( 2 ) 78 - 79 2004.4

Language：English Publishing type：Research paper (scientific journal) Publisher：SOC GLASS TECHNOLOGY

CaO-P2O5 glass ceramics with small additions of MgO and TiO2 were prepared in the ortho and pyrophosphate regions by powder sintering and crystallisation through heat treatment at different temperatures determined from, differential thermal analysis (DTA). The glass ceramics were analysed by x-ray diffraction (XRD) and it was observed that alpha- and beta-Ca2P2O7 were the first phases to precipitate in the parent glass matrix at a temperature of 681degreesC, followed by CaTi4(PO4)(6) and TiP2O7 at temperatures between 703 and 725degreesC The beta-Ca2P2O7 and CaTi4(PO4)(6) phases are usually considered as biocompatible and bioactive and, therefore, these glass ceramics seem to show good potential for bone regeneration applications.

In vitro bioactive nano-crystalline TiO2 layers grown at glass-coating/titanium interface Reviewed

Yongxing Liu, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 112 ( 1308 ) 452 - 457 2004

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

A new approach is presented to prepare a rutile layer on titanium substrates. According to this approach, pulverized glass, composed of 3CaO·4B2O3·3TiO2, is first developed on the substrate, heated up to 700 to 850°C, and then removed by soaking in hot water. During the heating process, rutile grew at the glass coating-substrate interface to form nano-sized crystallites. The rutile layer induced apatite formation within 3 d when soaked in simulated body fluid of the Kokubo recipe. Such in vitro bioactivity was attributed to many Ti-OH groups on the crystallite surface derived from hydrolysis of bonds at the crystallite-flux (matrix) interface like (rutile) -Ti-O-B or Ti-O-Ca-(the borate matrix).

DOI： 10.2109/jcersj.112.452

Topotaxial nucleation and growth of TiO2 submicron-scale rod arrays on titanium substrates via sodium tetraborate glass coating Reviewed

Yongxing Liu, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 112 ( 1310 ) 567 - 571 2004

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

A novel approach to fabricate sub-μm scale arrays is demonstrated with the growth of rutile TiO2 on titanium substrates. The fabrication process is template-free, simply involving coating of the titanium substrate with sodium tetraborate glass, Na2O · 2B2O 3: when the glass coating was removed by dissolution in distilled water at 80°C for about 5 h, random or well-ordered submicron-scale rod arrays of rutile were left on the substrate. A glass phase topotaxial (GPT) nucleation and growth mechanism is thought to operate in the crystal growth process.

DOI： 10.2109/jcersj.112.567

In vitro Platelet Adhesion and Protein Adsorption of Biomedical Implant Modified with Polysaccharide Reviewed

Tomohiko Yoshioka, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Transactions of the Materials Research Society of Japan 2004

TITANIA DERIVED FROM COMBINED CHEMICAL AND THERMAL TREATMENTS OF TITANIUM: IN VITRO APATITE FORMING ABILITY Reviewed

Akiyoshi Osaka, Kanji Tsuru, Satoshi Hayakawa

Phosphorus Research Bulletin 2004

Low-temperature preparation of anatase and rutile layers on titanium substrates and their ability to induce in vitro apatite deposition Reviewed

Jin-Ming Wu, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Journal of the American Ceramic Society 87 ( 9 ) 1635 - 1642 2004

Language：English Publishing type：Research paper (scientific journal) Publisher：American Ceramic Society

Surface modification of titanium and its alloys to induce apatite deposition within a short period is of practical importance in clinical applications. In this study, titanium substrates were treated with hydrogen peroxide solutions at low temperatures to yield titania layers consisting of anatase and rutile. Those titania layers, regardless of the fraction of anatase and rutile, were bioactive to induce deposition of apatite in Kokubo's simulated body fluid within 24 h. The bioactivity was attributed to both the epitaxial effect and the abundant Ti-OH group of the titania layer.

DOI： 10.1111/j.1551-2916.2004.01635.x

Potassium titanate nanorod arrays grown on titanium substrates and their in vitro bioactivity Reviewed

Yongxing Liu, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 112 ( 1312 ) 634 - 640 2004

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

A novel approach to fabricating highly-oriented, nm-scale potassium titanate K2Ti6O13 rod arrays on titanium substrates was demonstrated. The fabrication process was template-free, and simply involved coating the titanium substrates with pulverized potassium metaborate and its derivatives, and subsequent heating at 700°C for 5 h. When the samples were soaked in hot water, the coating layers were readily removed, leaving an array of titanate crystallites on the titanium substrates. Even the slightest change in the composition of the potassium borates resulted in various microstructures, while K2O·1.03B2O 3 yielded highly-oriented nanorod arrays of K2Ti 6O13. Bioactivity of the as-achieved nanorod arrays was proved by the deposition of apatite in simulated body fluid (SBF: Kokubo solution). When soaked in SBF, the K2Ti6O13 nanorod arrays deposited apatite within one day accompanying the release of potassium ions from the crystallites into SBF and the arrays were covered with apatite layers in three days. Ion exchange between the potassium ions in the crystal and calcium ions in SBF is proposed as the mechanism operative to favor the deposition of apatite.

DOI： 10.2109/jcersj.112.634

Bioactivity of metallic biomaterials with anatase layers deposited in acidic titanium tetrafluoride solution Reviewed

JM Wu, F Xiao, S Hayakawa, K Tsuru, S Takemoto, A Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 14 ( 12 ) 1027 - 1032 2003.12

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

A simple and versatile treatment was developed to provide various metallic biomaterials such as Ti, NiTi, Ta and SUS 316L stainless steel with in vitro bioactivity or ability to deposit carbonate-incorporated apatite in a simulated body fluid (Kokubo solution). A well-crystallized anatase layer deposited on the metallic biomaterials surfaces after soaking them at 60degreesC for 24 h in an aqueous solution of titanium tetrafluoride (40 mM) whose pH was adjusted to 1.9 with HCl;. The as-coated anatase layers did not deposit apatite. When heated at 300degreesC they were so bioactive as to deposit apatite within 5 day(s) in the Kokubo solution. The trace amount of fluorine weakly bound in the as-coated anatase layers was suggested to be one of the factors that suppressed the bioactivity. (C) 2003 Kluwer Academic Publishers.

DOI： 10.1023/B:JMSM.0000003998.37583.d7

Apatite deposition on thermally and anodically oxidized titanium surfaces in a simulated body fluid Reviewed

XX Wang, W Yan, S Hayakawa, K Tsuru, A Osaka

BIOMATERIALS 24 ( 25 ) 4631 - 4637 2003.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

By application of a special specimen set-LIP, thermally oxidized titanium specimen pairs were found able to deposit apatite oil the contact surfaces after soaking for 7 days in the simulated body fluid (SBF) of Kokubo's recipe. The specimens oxidized at 400degreesC and 500degreesC showed the highest ability of apatite deposition. Both increase and decrease in oxidation temperature front this range caused the apatite deposition ability to decrease. The specimen without treatment failed to deposit any apatite. Specimens anodically oxidized in electrolytes of H3PO4, H2SO4 and acetic acid exhibited very low ability of apatite deposition. Furthermore, the specimen thermally oxidized at 400degreesC was even able to help the surfaces of PTFE and silicone deposit apatite in the PTFE-Ti and silicone-Ti pairs. This in vitro experimental results indicated that the difference in apatite deposition among various titanium oxides does exist and can be distinguished by applying the present specimen set-up. The mechanism of the apatite deposition on the contact surfaces was discussed in relation to the passive dissolution of titanium in SBF. The release of titanium hydroxide and OH- ions from the titanium surfaces and their accumulation inside the confined space between the two contact surfaces were suggested to be responsible for the apatite deposition. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(03)00357-0

Structure and biomineralization of calcium silicate glasses containing fluoride ions Reviewed

E Fuji, K Kawabata, H Yoshimatsu, S Hayakawa, K Tsuru, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 111 ( 10 ) 762 - 766 2003.10

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

The in vitro bioactivity, in terms of apatite-forming ability, of calcium silicate glasses containing 10 mol% fluoride ions in the NaF-CaO-SiO2 system was examined by soaking in Kokubo's simulated body fluid (SBF) at 36.5degreesC for 7 d. The surface structure of the glasses was examined by thin-film X-ray diffraction (TF-XRD) and Fourier transform infrared reflection spectroscopy (FT-IR) in order to confirm the apatite deposition. The structure of the calcium silicate glasses was examined by Si-29 magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). Three calcium silicate glasses containing 10 mol% fluoride ions had different apatite-forming abilities. In the case of CaO/SiO2 = 1, the apatite-forming ability of 10NaF . 45CaO . 45SiO(2) was lower than that of 50CaO . 50SiO(2). This indicated that the addition of fluoride ions suppressed the apatite-forming ability, irrespective of the structural similarity of the silicate network based on the ratio of CaO/SiO2 between the glasses.

Sol-gel preparation of blood-compatible titania as an adsorbent of bilirubin Reviewed

T Asano, S Takemoto, K Tsuru, S Hayakawa, A Osaka, S Takashima

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 111 ( 9 ) 645 - 650 2003.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

This study concerns with the adsorption of pathogenic substances on highly blood-compatible titania and the adsorption mechanism. Titania was prepared through a sol-gel procedure by hydrolyzing tetraethylorthotitanate and calcining up to 705degreesC for 3 h. Pore size distribution and surface charge density were measured as a function of calcining temperature. Adsorption of bilirubin, as a typical pathogenic substance, as well as albumin on the titania powder was studied. Bilirubin was adsorbed either in 4 to 8-nm pores or on the surface with a higher positive charge. Thus, either entrapping bilirubin in the pores or electrostatic interaction between bilirubin and titania surface was effective for the adsorption of bilirubin. The titania powder adsorbed a greater amount of bilirubin than the anion-exchange resin used in clinics, hence they have potential for blood purification therapy.

In vitro apatite deposition on titania film derived from chemical treatment of Ti substrates with an oxysulfate solution containing hydrogen peroxide at low temperature Reviewed

F Xiao, K Tsuru, S Hayakawa, A Osaka

THIN SOLID FILMS 441 ( 1-2 ) 271 - 276 2003.9

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Thin titania film consisting of anatase and rutile was deposited on Ti substrates when soaked in a TiOSO4/H2O2 solution and aged in hot water. H2O2 corroded the Ti substrates, yielded a porous surface, and kept the solution from peptization. Thicker titania layers were formed in favor of both a greater supersaturation of Ti(IV) in the solution and a higher concentration of hydrated Ti(IV) derived by the corrosion of Ti and the hydrolysis of TiOSO4. The effects of aging in hot water were accounted for as they caused structural relaxation of the surface layer involving a rearrangement of Ti-OH and eliminating residual species like peroxide ions. Those titania layers were thus favored to deposit apatite when the Ti substrates were placed under a body environment, i.e. soaked in a simulated body fluid of Kokubo's recipe. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0040-6090(03)00913-1

Preparation of alginic acid layers on stainless-steel substrates for biomedical applications Reviewed

T Yoshioka, K Tsuru, S Hayakawa, A Osaka

BIOMATERIALS 24 ( 17 ) 2889 - 2894 2003.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

This study is concerned with the blood compatibility of alginic acid layers immobilized on gamma-aminopropyltriethoxysilane (gamma-APS)-grafted stainless-steel (SUS316L). The surfaces were characterized with contact angle measurement and X-ray photoelectron spectroscopy (XPS). The blood compatibility was evaluated in terms of platelet adhesion and blood clotting time. Ail in vitro platelet adhesion assay indicated that only a small number of platelets adhered to substrate surfaces modified with gamma-APS and subsequently with alginic acid. Moreover, alginic-acid-immobilized SUS316L substrates had little effect on the blood clotting time. This indicated that alginic-acid-immobilized SUS316L substrates do not adsorb some blood-clotting proteins or factors, or stimulate them. (C) 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(03)00127-3

Bioceramic coatings of titanium surfaces Reviewed

Jinming Wu, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Kuei Suan Jen Hsueh Pao/ Journal of the Chinese Ceramic Society 31 692 - 697 2003.7

The bioactive fixation between bone substitutes and their surrounding tissues is mostly studied in the nearest decade. The key of bioactive fixation is the high bioactivity of the biomaterials. To coat the titanium surface with a layer of bioceramics through physical deposition, sol-gel, electrochemical deposition, biomimetic process, etc. can promote the bioactivity of titanium effectively. Another approach to obtain a bioactive titanium surface is the chemical modification of titanium with sodium hydroxygen or hydrogen peroxide solution to induce titanium dioxide films on the surface. The titanium dioxide films derived by the surface modification should be abundant in Ti-OH functional groups, and also, in crystalline structure, which may effectively induce the epitaxial growth of hydroxylapatite nuclei. This paper provides a brief review of various techniques and their corresponding mechanisms for obtaining a titanium surface with bioactivity.

Bioactivity of viscoelastic Ormosil-type organic-inorganic hybrids containing colloidal silica particles Reviewed

Y Aburatani, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 111 ( 5 ) 318 - 322 2003.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Synthesized were organically modified silicate (ORMOSILs) hybrids containing colloidal silica as an ingredient, starting from poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate through sol-gel processing. The effects of pre-hydrolysis of TEOS on mechanical strength and viscoelasticity were examined. A sample of composition PDMS/TEOS = 0.60 (molar ratio) with pre-hydrolysis of TEOS showed about 65% maximum failure strain. Thus obtained hybrid exhibited a peak at around -75degreesC in the storage modulus-temperature curve of the hybrid, due to transverse movements of the PDMS chains. This hybrid, heated at 200degreesC deposited apatite within 1 d in the simulated body fluid of the Kokubo recipe.

Mechanical property and microstructure of bioactive organic-inorganic hybrids containing colloidal silica particles Reviewed

Y Aburatani, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 111 ( 4 ) 247 - 251 2003.4

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Synthesized through sol-gel processing were Ormosil type hybrid gels containing varied mass fractions of colloidal silica, poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate. Viscoelasticity, mechanical strength and Si-29 MAS NMR spectra were measured, and in vitro apatite deposition in a simulated body fluid (SBF) of the Kokubo recipe was examined. The relative height of a T-g peak at about -100degreesC in tan delta versus temperature curves grew with the colloidal silica content. This peak growth was accounted for the relative increase in PDMS-colloidal silica interactions. As the increase in the compressive strength followed the increase in colloidal silica content, the number of PDMS-silica bonds and hydrogen bond of colloidal silica increased due to the NMR spectra and tan delta curve. Thus, mechanical strength was dependent on PDMS-silica bonds and the hydrogen bond of colloidal silica. On the other hand, as the relative PDMS content increased, the number of PDMS-silica bonds was little influenced while PDMS chain structure increased. The gel (with a molar ratio TEOS: PDMS:H2O:HCl: Ca(NO3)(2).4H(2)O = 1:0.48:5.0:0.9:0.10) containing 14 mass% colloidal silica (CS14P0.48Ca0.10) exhibited the highest maximum failure strain (about 70%) among all samples. Thus, the relative content of PDMS chain structure depending on PDMS content influenced the maximum failure strain. CS14P0.48Ca0.25 could not deposit apatite within 7 d after soaking in SBF, while PDMS/TEOS = 0.24 (molar ratio) could deposit apatite within 3 d. The increase in PDMS content restrained the dissolution of Ca ions.

Structure and biomineralization of calcium silicate glasses containing fluoride ions Reviewed

Eiji Fuji, Koji Kawabata, Hideyuki Yoshimatsu, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 111 ( 1298 ) 762 - 766 2003.1

Language：English Publisher：The Ceramic Society of Japan

The in vitro bioactivity, in terms of apatite-forming ability, of calcium silicate glasses containing 10 mol% fluoride ions in the NaF-CaO-SiO2system was examined by soaking in Kokubo's simulated body fluid (SBF) at 36.5°C for 7 d. The surface structure of the glasses was examined by thin-film X-ray diffraction (TF-XRD) and Fourier transform infrared reflection spectroscopy (FT-IR) in order to confirm the apatite deposition. The structure of the calcium silicate glasses was examined by29Si magic angle spinning-nuclear resonance spectroscopy (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). Three calcium silicate glasses containing 10 mol% fluoride ions had different apatite-forming abilities. In the case of CaO/SiO2=1, the apatite-forming ability of 10NaF·45CaO·45SiO2was lower than that of 50CaO·50SiO2. This indicated that the addition of fluoride ions suppressed the apatite-forming ability, irrespective of the structural similarity of the silicate network based on the ratio of CaO/SiO2between the glasses.

DOI： 10.2109/jcersj.111.762

Mechanical property and microstructure of bioactive organic-inorganic hybrids containing colloidal silica particles Reviewed

Yasushi Aburatani, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 111 ( 1292 ) 247 - 251 2003

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Synthesized through sol-gel processing were Ormosil type hybrid gels containing varied mass fractions of colloidal silica, poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate. Viscoelasticity, mechanical strength and 29Si MAS NMR spectra were measured, and in vitro apatite deposition in a simulated body fluid (SBF) of the Kokubo recipe was examined. The relative height of a Tg peak at about - 100°C in tan δ versus temperature curves grew with the colloidal silica content. This peak growth was accounted for the relative increase in PDMS-colloidal silica interactions. As the increase in the compressive strength followed the increase in colloidal silica content, the number of PDMS-silica bonds and hydrogen bond of colloidal silica increased due to the NMR spectra and tan δ curve. Thus, mechanical strength was dependent on PDMS-silica bonds and the hydrogen bond of colloidal silica. On the other hand, as the relative PDMS content increased, the number of PDMS-silica bonds was little influenced while PDMS chain structure increased. The gel (with a molar ratio TEOS:PDMS:H2O:HCl:Ca (NO3)2·4H2O = 1:0.48:5.0:0.9:0.10) containing 14 mass% colloidal silica (CS14P0.48Ca0.10) exhibited the highest maximum failure strain (about 70%) among all samples. Thus, the relative content of PDMS chain structure depending on PDMS content influenced the maximum failure strain. CS14P0.48Ca0.25 could not deposit apatite within 7 d after soaking in SBF, while PDMS/TEOS = 0.24 (molar ratio) could deposit apatite within 3 d. The increase in PDMS content restrained the dissolution of Ca ions.

DOI： 10.2109/jcersj.111.247

Early Apatite Deposition onTitanium Treated by Hydrogen Peroxide Reviewed

Jin-Ming Wu, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

J. Aust, Ceram, Soc. 2003

Bioactivity of viscoelastic ormosil-type organic-inorganic hybrids containing colloidal silica particles Reviewed

Yasushi Aburatani, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of the Ceramic Society of Japan 111 ( 1293 ) 318 - 322 2003

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

Synthesized were organically modified silicate (ORMOSILs) hybrids containing colloidal silica as an ingredient, starting from poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate through sol-gel processing. The effects of pre-hydrolysis of TEOS on mechanical strength and viscoelasticity were examined. A sample of composition PDMS/TEOS = 0.60 (molar ratio) with pre-hydrolysis of TEOS showed about 65% maximum failure strain. Thus obtained hybrid exhibited a peak at around -75°C in the storage modulus-temperature curve of the hybrid, due to transverse movements of the PDMS chains. This hybrid, heated at 200°C deposited apatite within 1 d in the simulated body fluid of the Kokubo recipe.

DOI： 10.2109/jcersj.111.318

Sol-Gel Preparation of Blood-Compatible Titania as an Adsorbent of Bilirubin Reviewed

Takuji Asano, Shinji Takemoto, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka, Seisuke Takashima

Journal of the Ceramic Society of Japan 111 ( 1297 ) 645 - 650 2003

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

This study concerns with the adsorption of pathogenic substances on highly blood-compatible titania and the adsorption mechanism. Titania was prepared through a sol-gel procedure by hydrolyzing tetraethylor-thotitanate and calcining up to 705°C for 3 h. Pore size distribution and surface charge density were measured as a function of calcining temperature. Adsorption of bilirubin, as a typical pathogenic substance, as well as albumin on the titania powder was studied. Bilirubin was adsorbed either in 4 to 8-nm pores or on the surface with a higher positive charge. Thus, either entrapping bilirubin in the pores or electrostatic interaction between bilirubin and titania surface was effective for the adsorption of bilirubin. The titania powder adsorbed a greater amount of bilirubin than the anion-exchange resin used in clinics, hence they have potential for blood purification therapy.

DOI： 10.2109/jcersj.111.645

In vitro bioactivity of anatase film obtained by direct deposition from aqueous titanium tetrafluoride solutions Reviewed

JM Wu, S Hayakawa, K Tsuru, A Osaka

THIN SOLID FILMS 414 ( 2 ) 275 - 280 2002.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Well-crystallized anatase films were deposited on commercially available pure titanium substrates from an acid titanium tetrafluoride aqueous solution kept at 60 degreesC for 24 h. The anatase films consisted of dual layers that were different in topography: a dense inner layer strongly adhered to the Ti substrate and a porous outer layer. In vitro bioactivity of such films was evaluated by soaking them in a simulated body fluid (SBF) of the Kokubo solution to observe their ability to induce apatite deposition. The anatase films with a subsequent thermal treatment at a temperature range of 300-700 degreesC induced apatite deposition within 5 days. Apatite particles were also found to deposit within 7 days on the anatase films being heated at 800 degreesC, which involved much rutile due to direct air oxidation of the titanium substrate. When the heating temperature is lower than 200 degreesC, no apatite deposited on the films even after 10 days of soaking in the SBF solution. The improved in vitro bioactivity of the films subsequently heated over 300 degreesC was attributed to the elimination of fluorine. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0040-6090(02)00498-4

Soft solution approach to prepare crystalline titania films Reviewed

JM Wu, S Hayakawa, K Tsuru, A Osaka

SCRIPTA MATERIALIA 46 ( 10 ) 705 - 709 2002.5

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Titania films with crystal structures of anatase or a mixture of anatase and rutile were prepared through a soft solution approach. The crystalline titania film resulted from crystallization of the previously deposited amorphous gel in an acidic solution. A low pH value of the solution favored the formation of rutile. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S1359-6462(02)00056-8

Mechanical properties and microstructure of bioactive ORMOSILs containing silica particles Reviewed

Y Aburatani, K Tsuru, S Hayakawa, A Osaka

MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS 20 ( 1-2 ) 195 - 198 2002.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We synthesized organically modified silicate (ORMOSILs) gels with colloidal silica (CS) (AEROSIL(R)) starting from polydimethylsiloxane (PDMS), tetraethoxysilane (TEOS) and calcium nitrate (Ca(NO3)(2).4H(2)O) through sol-gel processing. Dynamic mechanical analysis indicated that relative height of the tandelta peak at about - 100 degreesC increased with an increase in the relative content of the inorganic components. This peak growth was accounted for by the relative increase in PDMS-colloidal silica particle interactions. The colloidal silica could control the mechanical behavior of the hybrids. The gel of a specific composition could deposit apatite within 3 days of soaking in the simulated body fluid (SBF), since it included many calcium ions on the surface. (C) 2002 Elsevier Science B.V All rights reserved.

DOI： 10.1016/S0928-4931(02)00032-2

Bioactive titania gel layers formed by chemical treatment of Ti substrate with a H2O2/HCl solution Reviewed

XX Wang, S Hayakawa, K Tsuru, A Osaka

BIOMATERIALS 23 ( 5 ) 1353 - 1357 2002.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a H2O2/0.1 M HCl solution tit 80degreesC. The thickness of the get layer increased almost linearly With the period of the treatment. A Subsequent heat treatment above 300degreesC transformed gradually the amorphous gel to the anatase crystal structure and the rutile started to appear after heat treatment at 600degreesC. Meanwhile, the densification of the gel occurred significantly after heat treatment above 700degreesC. e Similar to the sol-gel derived titania gel coatings, titania gel layers obtained in the present study exhibited in vitro apatite deposition C ability after the gel layers exceeded a minimum thickness (0.2 mum) and was subsequently heated in a proper temperature range (400-600degreesC). (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(01)00254-X

Nanocrystalline titania made from interactions of Ti with hydrogen peroxide solutions containing tantalum chloride Reviewed

JM Wu, S Hayakawa, K Tsuru, A Osaka

CRYSTAL GROWTH & DESIGN 2 ( 2 ) 147 - 149 2002.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Crystalline titania film and powders with crystallite size in the range of nanometers are of great interest in the fields of optical devices, gas sensors, catalysts, and biomaterials. This paper reports a soft solution approach to prepare crystalline titania. After Ti was soaked in hydrogen peroxide solutions containing 3.0 mM tantalum chloride at 80 degreesC for 3 days, crystalline titania films consisting of anatase and rutile were deposited on Ti substrates. While Ti was soaked in tantalum-free hydrogen peroxide solution followed by aging in hydrogen peroxide solution containing tantalum ions, titania films with well-crystallized anatase were obtained. The crystalline titania resulted from crystallization of the previously deposited amorphous gel. Addition of tantalum ions in hydrogen peroxide solutions helps to obtain the crystalline titania and favors especially the formation of rutile phase.

DOI： 10.1021/cg015535y

Crystallization of anatase from amorphous titania in hot water and in vitro biomineralization Reviewed

JM Wu, S Hayakawa, K Tsuru, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 110 ( 2 ) 78 - 80 2002.2

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Anatase of good crystallinity has been developed on titanium substrates by soaking in a 30 mass% hydrogen peroxide solution at 80degreesC for 8 h, soaking in distilled water at ambient temperature for 12 h, and subsequently aging in distilled water at 80degreesC for 3d. The anatase layers exhibit good bioactivity as inducing apatite deposition in Kokubo's simulated body fluid within 2d.

DOI： 10.2109/jcersj.110.78

Porous titania films prepared from interactions of titanium with hydrogen peroxide solution Reviewed

JM Wu, S Hayakawa, K Tsuru, A Osaka

SCRIPTA MATERIALIA 46 ( 1 ) 101 - 106 2002.1

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Anatase films with sub-micron porous structure were deposited homogeneously on Ti substrates by simply soaking in 15 wt.% hydrogen peroxide solution at 80 degreesC for 1 h followed by heating at 300 degreesC for 1 h in air. Deposition of the porous titania film was not sensitive to substrate morphology, whilst affected readily by the reaction rate. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S1359-6462(01)01207-6

Novel approach to fabricate porous gelatin-siloxane hybrids for bone tissue engineering Reviewed

Lei Ren, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Biomaterials 23 ( 24 ) 4765 - 4773 2002

Language：English Publishing type：Research paper (scientific journal)

Porous and bioactive gelatin-siloxane hybrids were successfully synthesized by using a combined sol-gel processing, post-gelation soaking, and freeze-drying process to provide a novel kind of materials in the developments and optimization of bone tissue engineering. The pore sizes of the hybrids can be well controlled by varying the freezing temperature. The scaffolds were soaked in a simulated body fluid (SBF) up to 14 days to evaluate the in vitro bioactivity. The Ca2+-containing scaffolds showed in vitro bioactivity as they biomimetically deposited apatite, but the Ca2+-free scaffolds failed. Cytotoxicity and cytocompatibility of those scaffolds and their extracts were monitored by the MC3T3-E1 cell responses, including the cell proliferation and the alkaline phosphatase activity. It was demonstrated that appropriate incorporation of Ca2+ ions stimulated osteoblast proliferation and differentiation in vitro. © 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(02)00226-0

Incorporation of Ca2+ ions in gelatin-siloxane hybrids through a sol-gel process Reviewed

L Ren, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 ( 5 ) 406 - 411 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Several gelatin-siloxane hybrids incorporating Ca2+ ions were synthesized through a sol-gel process starting with gelatin, 3-(glycidoxypropyl) trimethoxysilane (GPSM), and Ca(NO3)(2). Amino acid analysis, Si-29 NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and dynamic mechanical thermal analysis were used to assess the hybrid structure. It has been indicated that the grafting degree of epoxy groups of GPSM to gelatin and the extent of polymerization of methoxysilane end groups of GPSM strongly depended on the fraction of GPSM (f(G)) in the hybrids, but not on incorporation of Ca2+ ions. Hence, the hybrids with the same f(G) value, independent of incorporation of Ca2+ ions, had a similar cross-link density. However, the glass transition temperature (T-g) and storage modulus (E') around T-g decreased with incorporation of Ca2+ ions. Through the deconvolution of amide I bands of FT-IR spectra, flexibility may be interpreted by that the percentage of gelatin having a random structure increased with incorporation of Ca2+ ions. The Ca2+-containing hybrids can spontaneously deposit apatite when they were soaked in a simulated body fluid of the Kokubo recipe, showing their bioactivity.

DOI： 10.2109/jcersj.109.1269_406

Viscoelastic properties and bioactivity of sol-gel derived gelatin-silicate composites: Effects of the incorporated Ca2+ ions Reviewed

L Ren, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY 17 ( 3 ) 367 - 370 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：JOURNAL MATER SCI TECHNOL

Several gelatin-silicate composites, with or without incorporation of Ca2+ ions, were synthesized through set-gel processing starting from gelatin and 3- (glycidoxypropyl) trimethoxysilane. The structure around the Si atoms was similar for all the samples. The measurement of viscoelastic properties indicated that the glass transition temperature and activation energy decreased with the incorporation of Ca2+ ions. The Ca2+ ion-containing composites were bioactive as they spontaneously deposited apatite when soaked in a simulated body fluid of the Kokubo recipe.

Kinetics of apatite deposition of silica gel dependent on the inorganic ion composition of simulated body fluids Reviewed

K Tsuru, M Kubo, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 ( 5 ) 412 - 418 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Nucleation and crystal growth mechanism of apatite formation on porous silica gel derived by a sol-gel procedure was investigated by the use of several simulated body fluids (SBF's) that had different concentrations of Ca(II), P(V), and OH- but had the same degree of supersaturation for hydroxyapatite. Induction time of apatite crystallization in SBF's was evaluated by thin film X-ray diffractometry. The effect of each ion on the induction time increased in the order: Ca(II)-rich SBF <P(V)-rich SBF <much less than>OH--rich SBF, while that for the rate of initial crystal growth of apatite increased in the order: P (V)-rich SBF < Ca (II)-rich SBF < OH--rich SBF. It suggested that amorphous calcium phosphate (ACP) deposited as the precursor of apatite and ACP transformed into apatite nuclei by the incorporation of OH-. Moreover, the transformation was accelerated by large amount of ACP and was assisted by the rearrangement of silicate units in the gel surface. Ca(II) was richer in ACP deposited in Ca(II)-rich SBF and OH--rich SBF than that deposited in P (V) -rich SBF. Ca(II)-rich ACP was favorable for crystal growth.

DOI： 10.2109/jcersj.109.1269_412

In vivo evaluation of bone-bonding of titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride Reviewed

S Kaneko, K Tsuru, S Hayakawa, S Takemoto, C Ohtsuki, T Ozaki, H Inoue, A Osaka

BIOMATERIALS 22 ( 9 ) 875 - 881 2001.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Apatite formation on implants is important in achieving a direct bonding to bone tissue. We recently showed that titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride has the ability to form a hydroxyapatite layer in simulated body fluid which had inorganic ion composition similar to human blood plasma. In this study, a pure titanium cylinder (4.0 mm in diameter. 20.0 mm in length) treated with this method was implanted into a hole (4.2 mm in diameter) in a rabbit's tibia. After implantation for predetermined periods up to 16 weeks. the specimens were extracted with bone tissue, and were examined by push-out test to evaluate the shearing force between the implant and bone tissue. The results were compared with those of non-treated pure titanium. Eight weeks after surgery. the shearing force of the treated titanium implanted in the 4.2 mm-hole was significantly higher than that of non-treated titanium. although the surface roughness was not changed after the treatment. Scanning electron microscopic (SEM) observation and energy-dispersive X-my (EDX) microanalysis showed that the bone comes very close to the surface of the treated titanium. Moreover, the shearing force was higher for the implanted sample in the 4.0 mm-hole than that in the 4.2 mm-hole. Thus. it is confirmed that the treatment with hydrogen peroxide solution containing tantalum chloride provides higher bonding ability on titanium implants in vivo. (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(01)00036-9

A comparative study of in vitro apatite deposition on heat-, H2O2-, and NaOH-treated titanium surfaces Reviewed

XX Wang, S Hayakawa, K Tsuru, A Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 54 ( 2 ) 172 - 178 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Commercially pure titanium specimens are subjected to three different treatments, and their bioactivity are evaluated by immersing the specimens in a simulated body fluid (SBF, Kokubo's recipe) for various periods up to 7 days, with particular attention being paid to the differences in apatite deposition between surfaces open to SBF and surfaces in contact with the container's bottom. The treatment with a H2O2/HCl solution at 80 degreesC for 30 min followed by heating at 400 degreesC for 1 h produces an anatase titania gel layer on the specimen surface. This gel layer deposits apatite both on the contact and on open surfaces, and apatite deposition ability does not change with pre-staking in distilled water. The treatment with a NaOH solution at 60 degreesC for 3 days produces a sodium titanate gel layer. This gel layer can deposit apatite only on the contact surface, and the apatite deposition ability is completely lost after 1 day of pre-staking in distilled water. It is concluded, therefore, that the bioactivity of the titania gel originates from the favorable structure of the gel itself while the bioactivity of the sodium titanate gel depends heavily on ion release from the gel. The third treatment, a simple heat treatment at 400 degreesC for 1 h, produces a dense (not porous) oxide layer on the specimen surface. The specimens can deposit apatite on the contact surface after only 3 days of staking in SBF, but they cannot deposit apatite on the open surface for up to 2 months of staking. The implications of such apatite deposition behavior have been discussed in relation to the environments of titanium implants in bone as well as to the methodology of the SBF staking experiment. (C) 2000 John Wiley & Sons, Inc.

DOI： 10.1002/1097-4636(200102)54:2<172::AID-JBM3>3.0.CO;2-#

125Te, 27Al, and 71Ga NMR Study of M2O3-TeO2 (M = Al and Ga) Glasses Reviewed

Shinichi Sakida, Satoshi Hayakawa, Toshinobu Yoko

Journal of the American Ceramic Society 84 ( 4 ) 836 - 842 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：American Ceramic Society

The structures of M2O3-TeO2 (M = Al and Ga) glasses have been investigated by means of 125Te, 27Al, and 71Ga NMR spectroscopies. The structural units of respective cations in M2O3-TeO2 glasses were quantitatively analyzed. The fractions of TeO4 trigonal hipyramid. AlO6 and GaO6 octahedra decreased and those of TeO3 trigonal pyramid, AlO4, AlO5, and GaO4 polyhedra increased with increasing M2O3 content. Based on the local structures around Te, Al, and Ga atoms, the structure models of M2O3-TeO2 glasses were proposed.

DOI： 10.1111/j.1151-2916.2001.tb00749.x

Synthesis and in vitro behavior of organically modified silicate containing Ca ions Reviewed

K Tsuru, Y Aburatani, T Yabuta, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 89 - 96 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Organically modified silicates containing calcium ion have a potential to bond to bone via an apatite layer deposited on their surfaces in the body environment. In this study, we examined the relationship between apatite deposition and the microstructure of the organically modified silicates synthesized from tetraethoxysilane (TEOS) and poly (dimethylsiloxane) (PDMS) with a different amount of calcium nitrate tetrahydrate (Ca(NO3)(2). 4H(2)O) and hydrochloric acid (HCl). Apatite deposition was evaluated in vitro using a simulated body fluid (Kokubo solution). Copolymerization was confirmed between TEOS and PDMS even if PDMS free from -SiOH termination are used as one of the starting materials. The porosity and Ca content incorporated in the structure depended on the amount of HCl, whereas analysis of Si-29 MAS NMR spectra indicates that it caused few effects on the local structure around Si atoms. Apatite-forming ability is enhanced by optimal amounts of HCl and Ca (NO3)(2). 4H(2)O. The difference in apatite-forming ability among the hybrid gels was attributed to both Ca(II) contents in the structure and aggregation states of the Si-OH groups. Better bioactivity of the hybrid gels is achieved by the release of Ca(II) ions trapped in structure at gelation and the formation of hydrated silica rich in Si-OH.

DOI： 10.1023/A:1011217818285

In Vitro Biomimetic deposition of apatite on chemically and electrochemically treated titanium Reviewed

Akiyoshi Osaka, Satoshi Hayakawa, Kanji, Tsuru, Shinji Takemoto, Yasuhiro Kawabe, Shoko Iwatani

Journal of Australian Ceramics Society 2001

Highly blood compatible titania gel Reviewed

S Takemoto, K Tsuru, S Hayakawa, A Osaka, S Takashima

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 97 - 104 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

We examined blood compatibility of titania gels prepared through a sol-gel processing or yielded on titanium substrates by treating with hydrogen peroxide or simple heating. The blood compatibility was evaluated in terms of blood clotting time and correlated to the crystalline phases, roughness, specific surface area, and wettability. The sol-gel derived titania gel heated above 200 degreesC had good blood compatibility. Ti substrate treated with hydrogen peroxide and subsequently heated at 550 degreesC showed the best blood compatibility among the Ti substrates with or without the chemical treatment and heat-treatment. The specimen consisted of rutile and anatase phases, and had hydrophilic surface.

DOI： 10.1023/A:1011269802356

Synthesis and characterization of gelatin-siloxane hybrids derived through sol-gel procedure Reviewed

L Ren, K Tsuru, S Hayakawa, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 21 ( 1-2 ) 115 - 121 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

A new type of inorganic-organic hybrid materials incorporating gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was prepared through sol-gel processing. A solid-state Si-29 NMR analysis indicated that all the methoxy silane groups of GPSM were polymerized to yield -Si-O-Si- bridging bonds. An amino acid analysis confirmed grafting reactions of GPSM against gelatin chains. The increasing GPSM/gelatin ratio stimulated gel formation, phase separation, and the density of GPSM-crosslinking of the gelatin chains as well as it changed the micro- and macro- structures and the viscoelastic properties of the final products.

DOI： 10.1023/A:1011226104173

Sol-gel preparation and in vitro deposition of apatite on porous gelatin-siloxane hybrids Reviewed

Lei Ren, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka

Journal of Non-Crystalline Solids 285 ( 1-3 ) 116 - 122 2001

Language：English Publishing type：Research paper (scientific journal)

Ca(II) containing porous hybrids of gelatin and 3-(glycidoxypropyl)trimethoxysilane (GPSM) were prepared using a sol-gel process, post-gelation soaking, and freeze-drying. The porosity and pore size of the hybrids could be well controlled by the freezing temperature and the pH value of the soaking solution. The pore characteristics were related to the structure change during the soaking treatment. A second soaking of the porous hybrids introduced a binary-pore distribution. The rate of biodegradation in a trishydroxymethylaminomethane (Tris) buffer solution decreased with an increased GPSM content. A bone-like apatite layer was able to form in the Ca(II) containing porous gelatin-siloxane hybrids upon soaking in a stimulated body fluid (Kokubo recipe). These hybrid materials are proposed to find application as novel bioactive and biodegradable scaffolds in bone tissue engineering. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0022-3093(01)00441-0

Synthesis of bioactive organic-inorganic hybrids with gamma-methacryloxypropyltrimethoxysilane Reviewed

T Yabuta, K Tsuru, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 ( 1-3 ) 745 - 748 2000.12

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Bioactive organic-inorganic hybrids were synthesized through sol-gel processing starting from gamma -methacryloxypropyltrimethoxysilane. NMR-spectroscopic studies showed the presence of silanol groups (Si-OH) and Si-O-Si bonds. In vitro tests of the hybrids for bioactivity with a simulated body fluid (Kokubo solution) indicated that only calcium-containing hybrids could form apatite on their surfaces. Thus the presence of calcium ions was no less important to deposit apatite than the formation of silanol groups or Si-O-Si bonds.

DOI： 10.1023/A:1008795629804

Improvement of bioactivity of H2O2/TaCl5-treated titanium after subsequent heat treatments Reviewed

Xiao-Xiang Wang, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka

Journal of Biomedical Materials Research 52 ( 1 ) 171 - 176 2000.8

Language：English Publishing type：Research paper (scientific journal) Publisher：John Wiley & Sons Inc

Commercially pure titanium was treated with a H2O2/3 mM TaCl5 solution at 80°C for various periods and a titania gel layer was formed on the surface. This gel remained amorphous when heating for 1 h below 200°C and transformed to anatase after heating between 300°and 600°C. The anatase titania gel layers were found to be bioactive as to deposit carbonate ion- incorporated apatite within 1 day of immersion in the Kokubo solution, whereas the amorphous layers did not deposit apatite within 7 days. The apatite particles were found to nucleate preferentially inside the cracks prevailing in the thicker gel layers of 1-h chemically treated specimens. After immersing for 2 days, the titanium specimens were almost completely covered by apatite. Elimination of peroxide radicals from the titania gel and formation of anatase upon subsequent heating are considered to be responsible for the enhanced ability of apatite deposition. (C) 2000 John Wiley and Sons, Inc.

DOI： 10.1002/1097-4636(200010)52:1<171::AID-JBM22>3.0.CO;2-O

Te-125 and V-51 static NMR study of V2O5-TeO2 glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF PHYSICS-CONDENSED MATTER 12 ( 12 ) 2579 - 2595 2000.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The structures of V2O5-TeO2 glasses are investigated by means of Te-125 and V-51 static NMR spectroscopies and the local structures around the Te and V atoms are discussed in detail from the respective NMR spectra. The fraction of TeO3 trigonal pyramids increases and that of TeO4 trigonal bipyramids decreases with increasing V2O5 content. The structures of V2O5-TeO2 glasses are quite different from those of tellurite glasses containing network-modifying oxides. The fraction of VO4 tetrahedra increases and that of VO5 trigonal bipyramids decreases with increasing V2O5 content. Both chains consisting of tellurite structural units and those consisting of vanadate structural units contribute to the formation of the glass network in V2O5-TeO2 glasses.

DOI： 10.1088/0953-8984/12/12/302

Structure of lead oxyfluorosilicate glasses: X-ray photoelectron and nuclear magnetic resonance spectroscopy and molecular dynamics simulation Reviewed

Satoshi Hayakawa, Akiyoshi Osaka, Hironori Nishioka, Syuji Matsumoto, Yoshinari Miura

Journal of Non-Crystalline Solids 272 ( 2-3 ) 103 - 118 2000.1

Authorship：Lead author,　Corresponding author

X-ray photoelectron (XPS) and 29Si magic angle spinning (MAS)-NMR spectroscopy have been used to examine the chemical states of fluorine, oxygen, silicon and lead atoms in the glasses of composition xPbF2 · (100-y-x)PbO· ySiO2 (x = 0, 5, 10, 15, 20, 30 mol%, y = 30, 50, 60 mol%). The analysis of the F Is spectra indicated that Pb2+ and F- ions are preferentially located among the Si-O skeleton forming ionic Pb-F clusters. The fraction of the bridging (BO) and non-bridging oxygen (NBO) atoms was derived from the O 1s spectra. The network of the fluorine-containing glasses was concluded to depend on the ratio PbO/SiO2; when the ratio PbO/SiO2 was lower than 0.5, not only Pb atoms but also F atoms play a role as network modifiers, while when the ratio PbO/SiO2 is higher than 1.33, part of Pb atoms plays a role as a glass network former. © 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(00)00233-7

AMI study on infra-red spectra of silica clusters modified by fluorine Reviewed

Satoshi Hayakawa, Larry L. Hench

Journal of Non-Crystalline Solids 262 ( 1-3 ) 264 - 270 2000

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier

AM1 molecular orbital (MO) calculations were made for various cluster models of silica and for fluorinated silica. Calculations were made on clusters containing up to 12SiO4 units. On the basis of the relative position and relative intensity of the theoretical vibrational spectra of fluorine-free silica clusters with different sizes and fluorinated silica clusters, the effects of the replacement of OH groups by fluorine on the vibrational spectra of the silica clusters were established. In ring-type silica clusters the absorption around 640-720 cm-1, assignable to the ring vibration within the ring plane, could be seen in the three-membered ring. The intensity of absorption around 500-600 cm-1, assignable to the O-Si-O bending vibration, decreased with increasing size of rings and by the replacement of hydroxyl groups (OH-) by fluorine (F-). In block-type silica clusters all absorption peaks shifted to higher frequencies than those in ring-type silica clusters. The absorption peaks in AM1 calculated vibrational spectra correlated with the experimental IR spectra except for the stretching vibration of Si-F bonds. © 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(99)00664-X

Te-125 NMR study of MO-TeO2 (M=Mg, Zn, Sr, Ba and Pb) glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 107 ( 5 ) 395 - 402 1999.5

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

The structure of MO-TeO2 (RI Mg Zn, Sr, Ba and Pb) glasses has been studied by means of Te-125 static NMR technique. The fraction of TeO4, trigonal bipyramid (tbp), N-4 decreased and that of TeO3 trigonal pyramid (tp), N-3 increased almost linearly up to 33.3 mol% MO and rapidly in the range of 33.3 to 40 mol% MO, with increasing MO content, It was found that the glasses containing MO in the range of 40 to 45 mol% MO consisted only of TeO3 tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO4 tbp without a non-bridging oxygen (NBO) atom, TeO4/2 (N-4(0)), TeO4 tbp with an NBO atom, O-3/2 Te-O- (N-4(-)) and TeO3 tp with two NBO atoms, O1/2Te(= O)-O- (N-3(-)) were calculated. The structural change for MO-TeO2 glasses in the range of 0 to 33.3 mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO2 glasses containing more than 33.3 mol% MO has been proposed.

DOI： 10.2109/jcersj.107.395

¹²⁵Te NMR study of MO-TeO<inf>2</inf>(M = Mg, Zn, Sr, Ba and Pb) glasses Reviewed

Shinichi Sakida, Satoshi Hayakawa, Toshinobu Yoko

Journal of the Ceramic Society of Japan 107 395 - 402 1999.1

The structure of MO-TeO2(M=Mg, Zn, Sr, Ba and Pb) glasses has been studied by means of125Te static NMR technique. The fraction of TeO4trigonal bipyramid (tbp), N4decreased and that of TeO3trigonal pyramid (tp), N3increased almost linearly up to 33.3 mol% MO and rapidly in the range of 33.3 to 40 mol% MO, with increasing MO content. It was found that the glasses containing MO in the range of 40 to 45 mol% MO consisted only of TeO3tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO1tbp without a non-bridging oxygen (NBO) atom, TeO4/2(N40), TeO4tbp with an NBO atom, O3/2Te-O-(N4-) and TeO3tp with two NBO atoms, O1/2Te(=O)-O-(N3-) were calculated. The structural change for MO-TeO2glasses in the range of 0 to 33.3 mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO2glasses containing more than 33.3 mol% MO has been proposed.

Part 1. Te-125 NMR study of tellurite crystals Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS 243 ( 1 ) 1 - 12 1999.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Te-125 static and magic-angle spinning (MAS) NMR spectra of tellurite crystals with known crystal structures have been measured to determine the isotropic chemical shift delta(iso), the chemical shift anisotropy Delta delta and the asymmetry parameter eta. On the basis of structural unit, tellurite crystals are classified for convenience into TeO3 type (isolated TeO3 and terminal TeO3 type), TeO3+1 type and TeO4 type (alpha-TeO2 and beta-TeO2 type). As a result, the following relations were found: TeO3 greater than or equal to TeO3+1 approximate to beta-TeO2 > alpha-TeO2 in delta(iso(MAS)), beta-TeO2 greater than or equal to alpha-TeO2 > TeO3+1 > terminal TeO3 greater than or equal to isolated TeO3 in \Delta delta\ and TeO4 greater than or equal to TeO3+1 greater than or equal to TeO3 in eta. It was also found that the combination of \Delta delta\ and eta, namely, the relative values of delta(1), delta(2) and delta(3), can elucidate the local structure around Te atoms more definitely than delta(iso). This diagram is useful for examining the structures of tellurite crystals and glasses. (Glasses are discussed in another paper.) (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00811-4

Part 2. Te-125 NMR study of M2O-TeO2 (M = Li, Na, K, Rb and Cs) glasses Reviewed

S Sakida, S Hayakawa, T Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS 243 ( 1 ) 13 - 25 1999.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The structure of TeO2 and M2O-TeO2 (M = Li, Na, K, Rb and Cs) glasses has been investigated by means of Te-125 static and magic-angle spinning (MAS) NMR spectroscopies. On the basis of the relationship between the local structures around Te atoms and the NMR parameters obtained by Te-125 NMR spectra of various tellurite crystals, the local structures around Te atoms in TeO2 and M2O-TeO2 glasses were examined. The spectral simulation of static NMR spectra enabled us to discriminate between TeO3 trigonal pyramid (tp) and TeO4 trigonal bipyramid (tbp) and to estimate the fractions of TeO3 tp (N-3) and TeO4 tbp (N-4) It was concluded that in TeO2 glass TeO4 tbps are connected by sharing their corners as in alpha-TeO2 crystal. N-3 increased and NS decreased with increasing M2O content. On the basis of a previous structural model, the fractions of TeO4 tbp without a non-bridging oxygen (NBO) atom, TeO4 tbp with an NBO atom, and TeO3 tp with two NBO atoms were calculated. A new model which presents the structural change for M2O-TeO2 glasses has been proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00812-6

Molecular orbital models of silica clusters modified by fluorine Reviewed

S Hayakawa, LL Hench

JOURNAL OF NON-CRYSTALLINE SOLIDS 242 ( 2-3 ) 131 - 140 1998.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

AM1 molecular orbital calculations were conducted for various cluster models of silica and for those of fluorinated silica. Remarkably, the addition of HF to silica clusters gave an F-Si bond forming a trigonal bipyramid geometry around a 5-coordinated Si. The heat of addition reaction of HF was maximum for 4-membered rings and decreased with an increasing number of Si tetrahedra in ring-type silica clusters, while it increased with an increasing number of Si tetrahedra in block-type silica clusters. The addition reaction was strongly dependent on both whether there is sufficient structural flexibility around the Si sites to allow the formation of intramolecular hydrogen bonds with neighbouring silanol groups in the addition of HF and the degree of the strain of the arrangement for [SiO4/2F](-) The heat of reaction for the replacement of one hydroxyl group (OH-) by F- decreased with increasing number of Si tetrahedra. The replacement reaction was strongly dependent on both the size of the rings and the number of bridging oxygens per Si tetrahedron. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(98)00797-2

Ultrasonic implantation of calcium metasilicate glass particles into PMMA Reviewed

K Tsuru, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 9 ( 8 ) 479 - 484 1998.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

Polymer materials for clinical applications should be bioactive and have a bone-bonding ability. In order to provide poly(methyl methacrylate) (PMMA) with bioactivity, granules (<45 mu m) of a bioactive glass 50CaO . 50SiO(2) (mol %) were implanted into PMMA: they were suspended together with a piece of PMMA in a 40 tetrahydrofuran-60 ethanol (vol %) solution and ultrasonically agitated. The granules of <10 mu m in size were impregnated at similar to 40-20 mu m depth below the substrate surface. Two types were detected on the PMMA surface: (a) a glass-granule layer on PMMA, and (b) an inner granule layer, a PMMA layer, and an outer granule layer on the PM MA. The bioactivity of the implanted PMMA substrates was examined in vitro with a simulated body fluid (Kokubo solution). Apatite was precipitated on all glass granules and the whole substrate surfaces within 1 d. After 4 h soaking in the Kokubo solution, aggregates of apatite particles appeared on the substrate surface, independently of those on the glass granules, and they grew and proliferated on the whole subtrate surface in 7 d. Silica gel islands on PM MB due to the silicate an ions from the glass were considered to induce nucleation of the apatite particles.

DOI： 10.1023/A:1008875502451

An x-ray photoelectron spectroscopic study of the chemical states of fluorine atoms in calcium silicate glasses Reviewed

Satoshi Hayakawa, Akira Nakao, Chikara Ohtsutki, Akiyoshi Osaka, Shuji Matsumoto, Yoshinari Miura

Journal of Materials Research 13 ( 3 ) 739 - 743 1998.3

Authorship：Lead author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

X-ray photoelectron spectroscopy has been used to examine the chemical states of fluorine in the glasses of composition _{<italic>x</italic>}CaF₂(50 – <italic>x</italic>)CaO · 50SiO₂ (<italic>x</italic> = 5, 10, 15, 20, and 25 mol %) and _{<italic>x</italic>}CaF₂(50 – <italic>x</italic>/2)CaO(50 – <italic>x</italic>/2)SiO₂ (<italic>x</italic> = 5, 10, 15, and 20 mol %). The analysis of the F1_{<italic>s</italic>} spectra indicated that Ca²⁺ and F^- ions introduced as CaF₂ are favorably located among the Si–O skeleton forming Ca–F clusters. The fraction of the bridging and nonbridging oxygen atoms was derived from the O1_{<italic>s</italic>} spectra, and the network of the fluorine-containing glasses was concluded to depend only on the ratio CaO/SiO₂.

DOI： 10.1557/jmr.1998.0093

Properties of alumina-zirconia powder prepared from aluminium chelate compound and zirconium alkoxide Reviewed

K Kawabata, H Yoshimatsu, T Yabuki, A Kubotsu, S Hayakawa, A Osaka, Y Miura

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 106 ( 2 ) 155 - 159 1998.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Alumina-zirconia powder (AZ) was prepared by thermal decomposition of organic precursors synthesized from ethyl acetoacetate aluminium diisopropoxide and zirconium tetra-n-butoxide. The specific surface area of AZ was higher than that of alumina-zirconia powder (ALK) prepared from aluminium tri-sec-butoxide and zirconium tetra-n-butoxide in the range of 0-40 mol% ZrO2. The pore radius for AZ containing 0-40 mol% ZrO2 distributed from 1 to 3 nm. The true density of AZ was lower than that of ALK in the range of 0-40 mol% ZrO2. Four- and 6-coordinated Al atoms existed in ZrO2-free AZ, while 5-coordinated Al atoms in addition to 4- and 6-coordinated Al atoms existed in AZ containing 20-80 mol% ZrO2. These results indicate that alumina component and zirconia component in AZ were mixed homogeneously at the atomic level.

DOI： 10.2109/jcersj.106.155

Molecular dynamic simulation of heterogeneity and chemical states of fluorine in amorphous alkaline earth silicate systems Reviewed

Satoshi Hayakawa, Chikara Ohtsuki, Syuji Matsumoto, Akiyoshi Osaka, Yoshinari Miura

Computational Materials Science 9 ( 3-4 ) 337 - 342 1998.1

Bioactive gel coatings derived from vinyltrimethoxysilane Reviewed

K Tsuru, S Hayakawa, C Ohtsuki, A Osaka

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 13 ( 1-3 ) 237 - 240 1998

Language：English Publishing type：Research paper (scientific journal) Publisher：KLUWER ACADEMIC PUBL

An ethanol (EtOH) solution of polymerized vinyltrimethoxysilane (VTMS), about 20-mers, was mixed with an aqueous solution of calcium acetate (Ca(OAc)(2)) and refluxed in N-2 for 1 h to give sols of a typical composition VTMS:H2O:EtOH: Ca(OAc)(2) = 1 :9:8:0.05 (mol). Homogeneous films could be produced, by dip-coating, on Nylon(R) and soda-lime glass, but not on polypropylene or polytetrafluoroethylene. The gel films did not deposit apatite within 14 days of soaking in a simulated body fluid whereas films abraded with emery paper as well as bulk gels deposited apatite on the surfaces within 7 days, indicating the present gel was suitable for bioactive coatings on Nylon(R).

Apatite formation on the surface of silicone elastomer covered with bioactive glass particles Reviewed

Kanji Tsuru, Satoshi Hayakawa, Chikara Ohtsuki, Akiyoshi Osaka

Zairyo/Journal of the Society of Materials Science, Japan 47 ( 6 ) 565 - 570 1998

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Soc Mater Sci, Japan

Surface modification was applied to silicone elastomers via ultrasonic implantation of bioactive 50CaO · 50SiO2 (mol%) glass particles (&lt
45μm in diameter). Silicone elastomers with different hardness, which were sampled from an appropriate stage of their hardening process, were immersed in the bioactive glass-ethanol suspension and subjected to irradiation of ultrasonic energy. The glass particles wholly covered and well adhered to the surface of silicone elastomers when the glass was implanted in the silicone elastomer at the stage of hard gel. Thus the resulting composite formed apatite, which is essential for bone-bonding, in Kokubo solution within 7 days. The cross-sectional analysis of the composite soaked in Kokubo solution indicates that the composite is covered with a complexed layer consisting of the bioactive glass and the in situ formed apatite.

DOI： 10.2472/jsms.47.565

BIOMIMETIC COATING OF BONE-LIKE APATITE ON GLASS BEADS Reviewed

Akiyoshi OSAKA, Shinji TAKEMOTO, Satoshi HAYAKAWA, Chikara OHTSUKI

Journal of the Society of Materials Science, Japan 47 ( 3Appendix ) 60 - 63 1998

Language：English Publishing type：Research paper (scientific journal) Publisher：Society of Materials Science, Japan

Soda lime glass beads were chemically treated by either an aqueous solution of NaOH(3mol/l) or a hydrogen peroxide solution(30vol%)containing TaCl_5 in 5×10^3 mol/l or by both of them. The treated samples ware soaked up to 14 days in a simulated body fluid(SBF):Na^+142.0, K^+5.0, Ca^<2+> 2.5, Mg^<2+>1.5, Cl^-147.8, HCO_3^-4.2, HPO_4^<2->1.0, SO_4^<2->0.5(in 10^<-3>mol/l), or in another solution 1.5 times as concentrated as SBF(1.5SBF). The SBFs were kept at 36.5°C and at 7.25 in pH. Apatite was deposited on the samples treated with the NaOH solution, the H_2O_2/Ta solution, and both of them before soaking in 1.5SBF. Ta(V)ions were present on not only the samples treated with the H_2O_2/Ta solution but those treated with both NaOH and the H_2O_2/Ta solutions. It was concluded that Ta(V)ions on the surface layer had ability of inducing apatite deposition, and the ability was enhanced by the coexitence with silanol groups.

DOI： 10.2472/jsms.47.3appendix_60

Other Link： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=243528

Properties of Alumina-Zirconia Powder Prepared from Aluminium Chelate Compound and Zirconium Alkoxide Reviewed

KAWABATA Koji, YOSHIMATSU Hideyuki, YABUKI Tatsumi, KUBOTSU Akira, HAYAKAWA Satoshi, OSAKA Akiyoshi, MIURA Yoshinari

Journal of the Ceramic Society of Japan 106 ( 1230 ) 155 - 159 1998

Publisher：The Ceramic Society of Japan

Alumina-zirconia powder (AZ) was prepared by thermal decomposition of organic precursors synthesized from ethyl acetoacetate aluminium diisopropoxide and zirconium tetra-n-butoxide. The specific surface area of AZ was higher than that of alumina-zirconia powder (ALK) prepared from aluminium tri-sec-butoxide and zirconium tetra-n-butoxide in the range of 0-40mol% ZrO₂. The pore radius for AZ containing 0-40mol% ZrO₂ distributed from 1 to 3nm. The true density of AZ was lower than that of ALK in the range of 0-40mol% ZrO₂. Four- and 6-coordinated Al atoms existed in ZrO₂-free AZ, while 5-coordinated Al atoms in addition to 4- and 6-coordinated Al atoms existed in AZ containing 20-80mol% ZrO₂. These results indicate that alumina component and zirconia component in AZ were mixed homogeneously at the atomic level.

DOI： 10.2109/jcersj.106.155

DOI： 10.2472/jsms.56.526_references_DOI_WispPXNoq7EoLH9a3Rg9zT2nh5D

Other Link： http://id.ndl.go.jp/bib/4392630

Bioactivity of titanium treated with hydrogen peroxide solutions containing metal chlorides Reviewed

C Ohtsuki, H Iida, S Hayakawa, A Osaka

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 35 ( 1 ) 39 - 47 1997.4

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Commercially available pure metallic titanium was chemically treated at 60 degrees C for 24 h with H2O2 solutions containing various metal chlorides to provide titanium with bioactivity, that is, to give it the ability to form a biologically active bone-like apatite layer on the surface. After the chemical treatment the titanium specimens were soaked in a simulated body fluid (the Kokubo solution). Apatite was found to deposit on the specimens treated with the H2O2/TaCl5 and H2O2/SnCl2 solutions. X-ray photoelectron spectroscopic (XPS) study of the specimens treated with those H2O2 solutions indicated that basic Ti-OH groups in titania hydrogel layers on their surfaces were responsible for apatite nucleation and growth. (C) 1997 John Wiley & Sons, Inc.

DOI： 10.1002/(SICI)1097-4636(199704)35:1<39::AID-JBM5>3.0.CO;2-N

MAS-NMR studies of apatite formation on 50CaO・50SiO₂glass in a simulated body fluid(共著) Reviewed

Physics and Chemistry of Glasses 37 ( 5 ) 188 1996.12

³¹P MAS-NMR Studies of Phosphate Salts Formation on Calcium-Containing Oxide Glasses in a Simulated Body Fluid Reviewed

HAYAKAWA Satoshi, TSURU Kanji, IIDA Hirohisa, OHTSUKI Chikara, OSAKA Akiyoshi

Journal of the Ceramic Society of Japan 104 ( 1215 ) 1000 - 1003 1996.11

Authorship：Lead author,　Corresponding author Language：Japanese Publisher：The Ceramic Society of Japan

^<31>P MAS-NMR spectra were measured for pulverized binary and ternary glasses containing Ca^<2+> ions after soaking in a simulated body fluid (Kokubo solution; pH=7.25) for 1 d, and the chemical state of adsorbed phosphate ions were examined. The ^<31>P chemical shift indicated that orthophosphate ions, H_xPO_4^<-(3-x)>(0<x<3), were adsorbed on all the glasses but 60CaO・40Al_2O_3; pyrophosphate ions, H_zP_2O_7^<-(4-z)<(0<z<4), were detected on the aluminate glass, indicating that orthophosphate ions in the Kokubo solution were dimerized on the glass surface. For the glasses such as 60CaO・40Al_2O_3, 40CaO・60B_2O_3, 40aO・30B_2O_3・30Al_2O_3 and 40CaO・30B_2O_3・30SiO_2, those phosphate ions gave broad ^<31>P MAS-NMR spectra, hence have a broad distribution by coordinating to the various surface sites of the glasses. On the other hand, sharp ^<31>P MAS-NMR spectra as for a cortical bone (rabbit) were obtained for the rest of the glasses, 50CaO・50SiO_2 and 40CaO・30B_2O_3・30TiO_2, on which apatite formed in shorter soaking period in the Kokubo solution. It was thus concluded that presence of orthophosphate ions on the glass surfaces favored the deposition of apatite.

DOI： 10.2109/jcersj.104.1000

Other Link： https://jlc.jst.go.jp/DN/JALC/00370917762?from=CiNii

P-31 MAS-NMR studies of phosphate salts formation on calcium-containing oxide glasses in a simulated body fluid Reviewed

S Hayakawa, K Tsuru, H Iida, C Ohtsuki, A Osaka

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 104 ( 11 ) 1000 - 1003 1996.11

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

P-31 MAS-NMR spectra were measured for pulverized binary and ternary glasses containing Ca2+ ions after soaking in a simulated body fluid (Kokubo solution; pH=7.25) for 1 d, and the chemical state of adsorbed phosphate ions were examined. The P-31 chemical shift indicated that orthophosphate ions, H2PO4-(3-x) (0<x<3), were adsorbed on all the glasses but 60CaO . 40Al(2)O(3); pyrophosphate ions, H2P2O7-(4-x) (0<z<4), were detected on the aluminate glass, indicating that orthophosphate ions in the Kokubo solution were dimerized on the glass surface. For the glasses such as 60CaO . 40Al(2)O(3), 40CaO . 60B(2)O(3), 40CaO . 30B(2)O(3) . 30Al(2)O(3) and 40CaO . 30B(2)O(3) . 30SiO(2), those phosphate ions gave broad P-31 MAS-NMR spectra, hence have a broad distribution by coordinating to the various surface sites of the glasses. On the other hand, sharp P-31 MAS-NMR spectra as for a cortical bone (rabbit) were obtained for the rest of the glasses, (CaO)-Ca-50 . 50SiO(2) and 40CaO . 30B(2)O(3) . 30TiO(2), on which apatite formed in shorter soaking period in the Kokubo solution. It was thus concluded that presence of orthophosphate ions on the glass surfaces favored the deposition of apatite.

DOI： 10.2109/jcersj.104.1000

IR AND NMR STRUCTURAL STUDIES ON LEAD VANADATE GLASSES Reviewed

S HAYAKAWA, T YOKO, S SAKKA

JOURNAL OF NON-CRYSTALLINE SOLIDS 183 ( 1-2 ) 73 - 84 1995.4

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The structure of lead vanadate glasses, xPbO . (100 - x)V2O5, (x = 55, 50, 40, 30) has been investigated by means of infrared and V-51 static and magic angle spinning nuclear magnetic resonance (MAS-NMR) and Pb-207 MAS-NMR spectroscopies. The V-51 NMR spectral parameters of various constituent vanadate groups in lead vanadate glasses were determined by spectrum simulation on the basis of our previous results on alkaline earth vanadate glasses. The structure of 55PbO . 45V(2)O(5) glass mainly consists of VO4 tetrahedra, which are composed of V2O74- and (VO3)(n) single chains. The structure of xPbO . (100 - x)V2O5 glasses (x = 30, 40, 50) consists of both VO4 tetrahedra and VO5 trigonal bipyramids. These VOn polyhedra (n = 4, 5) compose at least four types of vanadate group, i.e., V2O74-, (VO3)(n) single chains, branched VO4 group and (V2O8)(n) zigzag chains depending on the PbO content.

DOI： 10.1016/0022-3093(94)00652-0

Structural studies on alkaline earth vanadate glasses (part 1) - IR spectroscopic study - Reviewed

Satoshi Hayakawa, Toshinobu Yoko, Sumio Sakka

Journal of the Ceramic Society of Japan. International ed. 102 ( 6 ) 522 - 528 1994.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Fuji Marketing Research Co Ltd

The structure of alkaline earth vanadate glasses of the compositions, xMO·(100-x)V2O5 (M = Mg, Ca, Sr, Ba, x = 30, 40, 45, 50, 55), has been investigated by means of IR spectroscopy with reference to various crystalline alkaline earth vanadates structurally known. It is found that the structure of alkaline earth vanadate glasses is very similar to each other and mainly consists of VO4-tetrahedra which form either (VO3)n-single chains as found in Sr(VO3)2 and Ba(VO3)2 crystals or the three dimensional arrangement of the corner-sharing branched VO4-tetrahedral groups as found in molten and amorphous V2O5. It is stressed that the glass network of the V2O5-rich glasses, 30MO·70V2O5, also mainly consists of VO4-tetrahedra.

Structural studies on alkaline earth vanadate glasses (part 2) - 51V NMR spectroscopic study - Reviewed

Satoshi Hayakawa, Toshinobu Yoko, Sumio Sakka

Journal of the Ceramic Society of Japan. International ed. 102 ( 6 ) 529 - 535 1994.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Fuji Marketing Research Co Ltd

The structure of alkaline earth vanadate glasses, xMO · (100-x)V2O5 (M = Ca, Sr, Ba, x = 30, 40, 45, 50, 55), has been investigated by means of 51V static and magic angle spinning (MAS) NMR spectroscopies. The 51V NMR spectral parameters of various constituent vanadate groups contained in the vanadate glasses were determined by the spectrum simulation with reference to those of various crystalline vanadates obtained previously. It was found that the structure of alkaline earth vanadate glasses consists mainly of VO4-tetrahedra in accordance with authors' previous results based on the IR study. It was deduced that for x = 50 the glass network is mainly constituted of one dimensional (VO3)n-single chains, and for x ≤ 45 the decrease of the MO content yields a mixture of the V2O5-rich phase constituted of three dimensionally branched VO4-groups and the MO-rich phase constituted of the VO5-trigonal bipyramids, followed by the decrease of (VO3)n-single chains.

51V NMR studies of crystalline monovalent and divalent metal metavanadates Reviewed

Satoshi Hayakawa, Toshinobu Yoko, Sumio Sakka

Journal of Solid State Chemistry 112 ( 2 ) 329 - 339 1994

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

51V static and magic-angle spinning (MAS) NMR spectra of crystalline monovalent metal metavanadates LiVO3, α- and βNaVO3, KVO3, CsVO3, β-AgVO3, and NH4VO3 and divalent metal metavanadates M(VO3)2 (M = Mg, Ca, Sr, Ba, Zn, Pb) have been measured in order to establish the relationships between the various NMR parameters, such as isotropic chemical shift, δiso, chemical shift anisotropy, |Δ
δ|, the asymmetry parameter, η, and the crystallographic parameters. When the structural units are the same, in this case VO4 tetrahedra or VO5 trigonal bipyramids, the δiso decrease almost linearly with decreasing average V-O bond length, independent of the polymerization degree and linkage mode of the VOn polyhedra. |Δ
δ|, increases with the polymerization degree and the degree of the structural distortion of the VOn polyhedron. It is found possible to predict the structural unit and the polymerization degree on the basis of the relation between |Δ
δ| and η. © 1994 Academic Press, Inc.

DOI： 10.1006/jssc.1994.1313

Structural Studies on Alkaline Earth Vanadate Glasses (Part 1) Reviewed

Satoshi HAYAKAWA, Toshinobu YOKO, Sumio SAKKA

Journal of the Ceramic Society of Japan 102 ( 1186 ) 522 - 529 1994

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

The structure of alkaline earth vanadate glasses of the compositions, _xMO・(100-x)V_2O_5 (M=Mg, Ca, Sr, Ba, x=30, 40, 45, 50, 55) , has been investigated by me ans of IR spectroscopy with reference to various crys talline alkaline earth vanadates structurally known. It is found that the structure of alkaline earth vanadate glasses is very similar to each other and mainly con sists of V0_4 tetrahedra which form either (VO_3) single chains as found in Sr (VO_3)_2 and Ba (VO_3)_2 crystals or the three dimensional arrangement of the corner sharing branched VO_4 tetrahedral groups as found in molten and amorphous V_2O_5. It is stressed that the glass network of the V_2O_5-rich glasses, 30MO・70V_2O_5, also mainly consists of VO_4 tetrahedra.

DOI： 10.2109/jcersj.102.522

⁵¹V NMR Studies of Crystalline Divalent Metal Vanadates and Divanadates Reviewed

Satoshi Hayakawa, Toshinobu Yoko, Sumio Sakka

Bulletin of the Chemical Society of Japan 66 ( 11 ) 3393 - 3400 1993.11

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：The Chemical Society of Japan

⁵¹V static and magic-angle spinning (MAS) NMR spectra of crystalline divalent metal vanadates, M₃(VO₄)₂ (M = Mg, Sr, Ba, Zn, Pb) and Mg₂M′(VO₄)₂ (M′ = Sr, Ba, Pb) and divanadates, M₂V₂O₇ (M = Mg, Ca, Sr, Ba, Zn, Pb) have been measured. In vanadates and dichromate-type divanadates, the ⁵¹V isotropic chemical shifts decrease linearly with decreasing electronegativity of divalent metal atom adjacent to the VO₄-tetrahedron. This was interpreted by considering that the electron density and the symmetry of VO₄-tetrahedron increases with decreasing electronegativity of divalent metal atom. This effect was more significant in vanadates than in divanadates. In divanadates the isotropic chemical shifts of the thortveitite-type configuration appeared at lower frequencies than that of the dichromate-type configuration. This was explained by assuming that the degree of s-hybridization of the oxygen orbitals in the V–O–V bonds is higher in the thortveitite-type than in the dichromate-type.

DOI： 10.1246/bcsj.66.3393

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