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Articles by Akiyoshi Osaka
Total Records ( 2 ) for Akiyoshi Osaka
  Atsushi Sugino , Chikara Ohtsuki , Kanji Tsuru , Satoshi Hayakawa , Takayoshi Nakano , Yoshimitsu Okazaki and Akiyoshi Osaka
  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 °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 °C in air showed no changes in metallographic structure, but not at 600 °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 μm 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 °C.
  Yuki Shirosaki , Kanji Tsuru , Satoshi Hayakawa , Akiyoshi Osaka , Maria Ascensao Lopes , Jose Domingos Santos , Maria Adelina Costa and Maria Helena Fernandes
  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 γ-glycidoxypropyltrimethoxysilane (GPTMS) concentration. Chitosan–silicate hybrids were synthesized using GPTMS as the reagent for cross-linking of the chitosan chains. Fourier transform infrared spectroscopy, 29Si 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).
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