Faculty Profiles - HAYAKAWA Satoshi

Papers - HAYAKAWA Satoshi

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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

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