研究者詳細 - 早川　聡

Acceleration of apatite nucleation on parallel aligned Ti-substrates with optimum gaps by UV-light Pre-irradiation

Satoshi Hayakawa, Keita Uetsuki, Akinori Kochi, Yuki Shirosaki, Akiyoshi Osaka

Key Engineering Materials 493-494 936 - 939 2012年

記述言語：英語

A recently developed "GRAPE® 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, pure titanium pieces were thermally oxidized in air and pre-irradiated by UV-light under different environmental conditions such as in air or in ultra-pure water before aligning pairs of specimens in the GRAPE® set-up, i.e., two pieces of titanium substrates were aligned parallel to each other with optimum gap width (spatial design). Then, they were soaked in Kokubo's simulated body fluid (SBF, pH7.4, 36.5°C) for 1-2 days to clarify how the UV-light pre-irradiation affects the in vitro apatite nucleation on the substrates under the specific spatial design. UV-light pre-irradiation in water led to the deposition of a large number of apatite particles within 1 day, and showed apatite X-ray diffraction, although UV-light pre-irradiation in air and non-pretreated specimens gave the deposition of a few apatite particles and did not show any apatite X-ray diffraction. These results indicated that the rate of primary heterogeneous nucleation of apatite increased by UV-light pre-irradiation in ultra-pure water. TFXRD patterns of the surface of the substrates thermally oxidized in air at 500°C showed the peak at 2θ= 27° assignable to the 110 diffraction of rutile phase of titanium dioxide (ICDD-JCPDS data #21-1276). Previous studies reported that the primary heterogeneous nucleation must be induced by Ti-OH groups on titanium oxide layer. Probably, the UV-light pre-irradiation in ultra-pure water can increase the number of Ti-OH groups on the surface, resulting in accelerated primary heterogeneous nucleation of apatite. © (2012) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/KEM.493-494.936

Preparation of injectable hydroxyapatite/collagen nanocomposite artificial bone

Akinori Kochi, Masanori Kikuchi, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

Key Engineering Materials 493-494 689 - 692 2012年

記述言語：英語

Injectable hydroxyapatite/collagen nanocomposite (HAp/Col) artificial bone was prepared utilizing gelation of sodium alginate (Na-Alg). Mass ratio of the HAp/Col powder, with or without Ca adsorption treatment and Na-Alg (80-120, 300-400, 500-600 cP in viscosity at 10 g/dm 3) was fixed at 90/10. Injectable HAp/Col was prepared by mixing the HAp/Col powder with Na-Alg solution at several powder (HAp/Col)/liquid (Na-Alg solution) ratios (P/L ratio, g/cm 3). The result of consistency measurement suggested that the operability of injectable HAp/Col paste could be controlled by both the P/L ratio and the viscosity of Na-Alg solution. According to the consistency measurement and practical feelings during mixing, P/L=1/1.67 (80-120 cP) and 1/1.89 (300-400, 500-600 cP) were considered to be the highest P/L ratio allowed to mix the HAp/Col paste with a spatula. At the P/L=1/2.33 (80-120 cP), the paste prepared with the non-treated HAp/Col powder, placed in an incubator (37 °C,relative humidity 100%) for 24h, demonstrated gellike property, while the paste prepared with Ca-treated HAp/Col powder did putty-like property. The difference in their property might be caused by the initial bonding behavior between Alg and Ca 2+ after mixing. The setting time measurement with Gillmore needle was impossible because they were toosoft for this method. Even though, their operability and coalescence/settingproperty could be used as the injectable bone filler. © (2012) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/KEM.493-494.689

Chitosan-silicate hybrids via sol-gel method for scaffold applications

第28回日韓国際セラミックスセミナーとその周辺

城崎由紀, 早川聡, 中村有里, 尾坂明義

マテリアルインテグレーション 25 ( 2 ) 9 - 12 2012年

Yuki Shirosaki, Akiyoshi Osaka, Satoshi Hayakawa, Kanji Tsuru

Handbook of Chitosan Research and Applications 327 - 336 2011年2月

Novel strategies for regenerating or reconstructing damaged bone tissues are of urgent necessity, because of limitations in conventional therapies for trauma, congenital defects, cancer, and other bone diseases. The tissue engineering approach to repair and regeneration is founded upon the use of biodegradable polymer scaffolds, which may manipulate bone cell functions, encourage the migration of bone cells from border areas to the defect site, and provide a source of inductive factors to support bone cell differentiation. During the past decades, scaffolds from natural biodegradable polymers such as collagen, gelatin, fibrin, and alginates, or synthetic biodegradable polymers such as polyglycolide, polylactides, and copolymers of glycolide with lactides have been extensively explored. On the other hand, it has been confirmed that the bonelike apatite layer, deposited spontaneously on the biomaterial surfaces, can enhance osteoconductivity. The presence of such bone-like apatite layers is also believed to be a prerequisite to conduction of osteogenic cells into various porous scaffolds or onto the surface of bioactive glasses. The formation of such bone-like apatite is favored by the cooperative behavior of a hydrated silica or titania gel surface with many Si-OH or Ti- OH groups, and calcium ions to be released into the body fluid when implanted. Thus, hybrid materials derived from the integration of biodegradable polymers with bioactive inorganic species may construct a new group of scaffolds appropriate for tissue engineering. Moreover, tissue engineering approach depends on the use of porous scaffolds that serve to support and reinforce the regenerating tissue. Controlled porous structures of these scaffolds allow cell attachment and migration, tissue generation, or vascularization. We have been studying the synthesis of novel chitosan-silicate hybrids derived from the integration of chitosan and γ-glycidoxypropyltrimethoxysilane (GPTMS). We introduce some of the results on this hybrid for biomedical application. © 2012 by Nova Science Publishers, Inc. All rights reserved.

Apatite nano-rods array grown on glass substrates in aqueous systems

Contrary effects of UV-irradiation on in vitro apatite-forming ability of TiO2 layer in simulated body fluid 査読

Keita Uetsuki, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

Bioceramics Development and Applications 1 2011年2月

A. Osaka, Y. Shirosaki, S. Hayakawa, K. Tsuru, E. Fujii, K. Kawabata

Ceramic Transactions 228 83 - 88 2011年1月

Fabrication of an assembly of nm-sized rods or wires of hydroxyapatite (HAp) would mimic the structure of dentin or enamel when they are tailored to align each other along a specific crystallographic axis. This study proposed new strategy for self-assembling one-dimensional HAp nano-rods with an organized superstructure. We prepared a nm-scale rod array of HAp having preferred orientation to the c-axis simply by soaking calcium-containing silicate glass substrates in aqueous Na2HPO4 solutions at 80°C for various periods, as inspired by the glass-apatite conversion procedure. Those HAp rods grew up perpendicularly to the glass surface, and the crystallites covered the glass entire surface uniformly, resulting in "dental enamel-like" rod array structure.

PREPARATION AND PROTEIN ADSORPTION OF SILICA-BASED COMPOSITE PARTICLES FOR BLOOD PURIFICATION THERAPY

Jie Li, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

ADVANCES IN BIOCERAMICS AND POROUS CERAMICS IV 32 13 - 18 2011年

記述言語：英語出版者・発行元：AMER CERAMIC SOC

Silica gel macrospheres of a few millimeters in diameter were fabricated via the sol-gel route using water glass, calcium chloride, and sodium alginate as the precursor components. TiO2 coating on the silica gel macrosphere surface was conducted by soaking them in titania sol derived from hydrolysis of tetraethylorthotitanate (TEOT) under varied pH (HNO3), and temperature (50 similar to 80 degrees C). X-ray diffraction analysis indicated deposition of anatase, and particular deposition (<1 mu m) on the surface was confirmed by scanning electron microscopy. Protein adsorption behavior was examined as a function of pH of the hydrolysis of TEOT, using bovine serum albumin (BSA) and lysozyme (LSZ) as the model proteins. BSA adsorption was little affected by the pH, while some effects were found for LSZ adsorption. BSA adsorption saturated at 20 similar to 25 min contact, while LSZ adsorption took longer time for the saturation. Moreover, BSA was adsorbed almost twice as much as LSZ, when saturation adsorption was compared. An effect of residual calcium ions with better affinity to BSA was proposed for partial interpretation since surface charge could not account for those adsorption behaviors.

GRAPE® Technology or bone-like apatite deposition in narrow grooves

ガラスやガラスセラミックの生体安全性

早川聡, 城﨑由紀, 都留寛治, 尾坂明義

NEW GLASS 26 ( 4 ) 16 - 20 2011年

Preparation of injectable artificial bone fabricated from hydroxyapatite/collagen nanocomposite

Akinori Kochi, Masanori Kikuchi, Yuki Shirosaki, Satoshi Hayakawa, Akiyoshi Osaka

World Journal of Engineering 1 585 - 586 2011年

空間デザインと熱酸化による骨親和性の向上

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

セラミックス 46 ( 4 ) 293 - 297 2011年

A. Sugino, K. Uetsuki, K. Kuramoto, S. Hayakawa, Y. Shirosaki, A. Osaka, K. Tsuru, T. Nakano, C. Ohtsuki

Ceramic Engineering and Science Proceedings 31 57 - 62 2010年12月

Among several techniques proposed for fixing titanium bone implant in bone tissues by inducing apatite deposition on the implant surface, "GRAPE® Technology" is the simplest one, where optimum size of macro-grooving and heating in air are provided for pure titanium because samples with such grooves deposit apatite when soaked in an aqueous solution mimicking human blood plasma. The technique is needed to be confirmed by in vivo tests if it is effective for bone tissues, or if it is applicable to newly developed titanium alloy systems. In this study, the validity of GRAPE® Technology for a Ti-15Zr-4Ta-4Nb alloy was assessed with both in vitro and in vivo experiments. Here, alloy pieces with macro-grooves 500 μm in depth and 500 μm in width were heated at 500°C to induce thin titania layers on the surface. In vivo tests confirmed bone-ingrowth within 3 weeks in the samples with the macro-grooves but very less for those without the grooves. Those results indicated that GRAPE® Technology is effective for providing the Ti-15Zr-4Ta-4Nb-based implants with osteoconductivity.

チタン系インプラントの表面改質--酸化チタン層への紫外線照射による生体親和性の向上

早川聡, 尾坂明義, 城崎由紀

チタン 58 ( 2 ) 146 - 150 2010年4月

0932 GRAPE^[○!R] Technology : 空間デザインによりチタン製人工関節に骨伝導能を付与する新しい手法(OS20-1:人工関節とバイオエンジニアリング1)

杉野篤史, 都留寛治, 早川聡, 城崎由紀, 大槻主税, 尾坂明義

バイオエンジニアリング講演会講演論文集 2009 ( 22 ) 344 - 344 2010年1月

PREPARATION OF HYDROXYAPATITE NANOPARTICLES APPLYING THE MICRO CHEMICAL PROCESS

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

ADVANCES IN BIOCERAMICS AND BIOTECHNOLOGIES 218 185 - + 2010年

記述言語：英語出版者・発行元：AMER CERAMIC SOC

A micro-chemical process was applied to prepare nanometer-size hydroxyapatite (HA) particles with various shapes and sizes so as to provide high surface activities, where solutions of reagent-grade calcium nitrate tetrahydrate and diammonium hydrogen phosphate were introduced in a micro reactor. The particles were characterized by X-ray diffractometry, transmission electron microscopy, or inductively coupled plasma photometry. Particle size and shape were dependent on not only pH and concentration of the mixing solutions but also the flow rate. Dilute solutions containing 3 mM Ca(II) and 5 mM P(V) yielded spherical HA particles, whose average particle size increased from about 3 nm to 40 nm as the flow rate increased from 0.3 to 3 ml.min(-1), where pH and the temperature of the reaction system were respectively maintained at 10 and at 40 degrees C. Concentrated solutions with 50 mM Ca(II) and 30 mM P(V) yielded rectangular plate-like HA particles, 300 am long and 50 nm wide, when pH was kept at 8, while agglomerations of smaller HA particles of about 20-50 am were obtained when pH was kept at 10.

CELL PROLIFERATION ON NANO-STRUCTURED TITANIUM OXIDE LAYER PREPARED ON TITANIUM SUBSTRATES

Satoshi Hayakawa, Koji Kawanishi, Yuki Shirosaki, Akiyoshi Osaka

ADVANCES IN BIOCERAMICS AND BIOTECHNOLOGIES 218 205 - 212 2010年

記述言語：英語出版者・発行元：AMER CERAMIC SOC

Effects of nanometer-scale surface roughness of titanium oxide layer on the adhesion and proliferation of osteoblast-like cell were examined. The nano-structured titanium oxide layer was prepared on titanium substrates by chemical treatment and heat-treatment. The anatase or rutile phase of titanium oxide was formed on the titanium substrates. The surface roughness of titanium oxide layer depended on the chemical treatment time or the heat-treatment time. The average roughness (Sa) was controlled in the range from 10 to 70 nm. The cell metabolic activity increased on the substrate with limited surface roughness. It is found that cell proliferation is affected by nanometer-scale surface roughness of titanium oxide layer.

ONE-STEP PREPARATION OF ORGANOSILOXANE-DERIVED SILICA PARTICLES

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

ADVANCES IN BIOCERAMICS AND POROUS CERAMICS II 30 ( 6 ) 3 - + 2010年

記述言語：英語出版者・発行元：AMER CERAMIC SOC

Silica particles and their derivatives with meso-structure attracted much attention, but they were synthesized through complicated multi-step procedure. Considering biomedical application, no surfactants, used in almost all cases above, should be employable due to fear of their toxicity. The present study explored one-step sol-gel preparation of silica particles with biomedical functionalities, starting from Stober-type systems, and characterized by Transmission Electron Micrograph or Si-29 MAS NMR spectroscopy. The Ca-containing particles, derived from the precursor system tetraethoxysilane (TEOS)-H2O-C2H5OH (EtOH)-CaCl2-NH4OH, consisted of primary particles of similar to 10 nm, and were spherical in shape with the diameter of similar to 1000 run, where Ca bridged Si-O- on the opposite particle surface. In contrast, the Ca-free particles were smaller with 400 similar to 500 nm in size due to the absence of such bridging effects. In addition, the Ca-containing ones deposited petal-like apatite within one week in Kokubo's simulated body fluid (SBF), which was interpreted in terms of the Ca release from the particles. Amino-modified silica particles were derived from the sol-gel precursor system aminopropyltriethoxysilane (APTES)-TEOS-H2O-EtOH where APTES behaved not only as the catalyst but also a reactant; i.e., this was a self-catalyzed sol-gel system. Hydrogen bonding among the amino group of APTES on one particle surface and with Si-O- on the other was suggested to work in agglomeration of the primary particles. Bovine serum albumin was covalently fixed on the APTES-silica surface, suggesting their applicability of proteins or other growth factor delivery.