Faculty Profiles - HAYAKAWA Satoshi

Papers - HAYAKAWA Satoshi

Division display 21 - 40 of about 196 ／ All the affair displays >>

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

　 PREV - NEXT 　

1
2
3
4
5
6
7
8
9
10