Biomaterials Engineering (Biomaterials Laboratory), Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University

Highly-oriented hydroxyapatite crystals

Fully developed mature dental enamel is a highly orga- nized structure of enamel prisms that consist of bundles of nanorod-like hydroxyapatite (HAp) crystals arranged roughly parallel to each other. 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 phosphoric salt solution.

1) S. Hayakawa, Y. Li, K. Tsuru, A. Osaka, E. Fujii, K. Kawabata, "Preparation of Nanometer-scale Rod Array of Hydroxyapatite Crystal", Acta Biomaterialia, 5[6], 2152-2160 (2009).

Ion-substituted hydroxyapatite

Lattice structure and its disorder of hydroxyapatite (HAp) influence biodegradability, and amorphous (disordered) surface layer of HAp can adsorb physiological active substance such as cellular growth factor. The oxoacid ion-induced HAp is synthesized, and relation between local structure around oxoacid ion in HAp and characteristics of HAp is investigated.

1) S. Hayakawa, T. Kanaya, K. Tsuru, Y. Shirosaki, A. Osaka, E. Fujii, K. Kawabata, G. Gasqueres, C. Bonhomme, F. Babonneau, C. Jaeger, H.J. Kleebe, "Heterogeneous structure and in vitro degradation behavior of wet-chemically derived nanocrystalline silicon-containing hydroxyapatite particles", Acta Biomaterialia, 9[1], 4856-4867 (2013).
2) S. Barheine, S. Hayakawa, A. Osaka, C. Jaeger, "Surface, Interface and Bulk Structure of Borate Containing Apatitic Biomaterials", Chemistry of Materials, 21[14], 3102-3109 (2009).

Surface treatment of titanium for enhanced bioactibity

Surface modifications of titanium or titanium-alloy implants are essential in cementless fixation because these materials cannot bond to living bone. We investigate the surface-modification conditions of these implants using chemical, heat, and electrochemical treatment methods to develop the implants with direct bonding capability to living bone.

GRAPE^® Technology (GRoove and APatitE)

Our research group and Nakashima Medical Co., Ltd. developed the extremely simple technique for providing the spontaneous apatite-forming ability to titanium by both spatial design and thermal oxidation, denoted as “GRAPE technology”. Pure titanium with machined micro-groove of less than 800 μm in depth and 1000 μm in width and thermally oxidized at 400°C in air induced apatite deposition in the internal space of micro-grooves during exposure to simulated body fluid (SBF).

1) K. Uetsuki, S. Nakai, Y. Shirosaki, S. Hayakawa, A. Osaka, "Nucleation and growth of apatite on an anatase layer irradiated with UV light under different environmental conditions", Journal of Biomedical Materials Research, 101A[3], 712-719 (2013).
2) A. Sugino, C. Ohtsuki, K. Tsuru, S. Hayakawa, T. Nakano, Y. Okazaki, A. Osaka, "Effect of spatial design and thermal oxidation on apatite formation on Ti-15Zr-4Ta-4Nb alloy", Acta Biomaterialia, 5, 298-304 (2009).

3) A. Sugino, K. Tsuru, S. Hayakawa, K. Kikuta, G. Kawachi, A. Osaka, C. Ohtsuki, "Induced deposition of bone-like hydroxyapatite on thermally oxidized titanium substrates using a spatial gap in a solution that mimics a body fluid", Journal of the Ceramic Society of Japan, 117, 515-520 (2009).

4) J-M. Wu, S. Hayakawa, K. Tsuru, A. Osaka, "Low-temperature Preparation of Anatase and Rutile Layers on Titanium Substrates and Their Ability To Induce in Vitro Apatite Deposition", J. Am. Ceram. Soc., 87[9], 1635-1642 (2004).

Prof. Jinming Wu (Zhejiang University)

5) X-X. Wang, W. Yan, S. Hayakawa, K. Tsuru, A. Osaka, "Apatite deposition on thermally and anodically oxidized titanium surfaces in a simulated body fluid", Biomaterials, 24, 4631-4637 (2003).

Prof. Xiao-Xiang Wang (Zhejiang University)

Organic-inorganic hybrid scaffolds for tissue engineering

Chitosan is biodegradable, biocompatible, non-antigenic and non-toxic material, and Si(IV) stimulates bone ingrowth, hence organic-inorganic hybrids consisting of chitosan and organosiloxanes will be candidates for biomedical applications and tissue engineering. We try to develop flexible, osteoconductive, and biodegradable organic-inorganic hybrid materials.

1) Yuki Shirosaki, “Preparation of organic-inorganic hybrids with silicate network for the medical applications”, Journal of the Ceramic Society of Japan, 120 [12], 555-559 (2012).

2) Y. Shirosaki, K. Tsuru, H. Moribayashi, S. Hayakawa, Y. Nakamura, I.R. Gibson, A. Osaka, “Preparation of osteocompatible Si(IV)-enriched chitosan-silicate hybrids”, Journal of the Ceramic Society of Japan, 118[11], 989-992 (2010).

3) Y. Shirosaki, K. Tsuru, S. Hayakawa, A. Osaka, M.A. Lopes, J.D. Santos, M.A. Costa, M.H. Fernandes, “Physical, chemical and in vitro biological profile of chitosan hybrid membrane as a function of organosiloxane concentration”, Acta Biomaterialia, 5[1], 346-355 (2009).