Papers by Author: Takeshi Yao

Abstract: In this study, we aimed to introduce bioactivity to bioinert zirconia by performing sandblasting process and subsequently depositing apatite nuclei (AN), which are fine particles of calcium phosphate precipitated by raising pH of SBF, on the surface of the zirconia samples. By soaking the AN treated zirconia samples in SBF, hydroxyapatite formation was observed in 1 day and high hydroxyapatite-forming ability was attained.

Abstract: Ti-12Ta-9Nb-6Zr-3V-O alloy, one of the shape-memory alloys with lower Young’s modulus in comparison with conventional titanium alloy, was treated with sulfuric acid to form roughened surface on the substrate. In order to impart hydroxyapatite formation ability to the Ti-12Ta-9Nb-6Zr-3V-O alloy, apatite nuclei (AN) were precipitated on the roughened surface using simulated body fluid (SBF) adjusted at higher pH than physiological condition. By this treatment, AN-precipitated Ti-12Ta-9Nb-6Zr-3V-O alloy was obtained. The AN-precipitated Ti-12Ta-9Nb-6Zr-3V-O alloy showed high hydroxyapatite formation ability in physiological SBF.

Abstract: Cellulose nanofiber-apatite nuclei composites were fabricated by mixing apatite nuclei with cellulose nanofiber slurry and air-drying. Then apatite-forming ability could be imparted to cellulose nanofiber-apatite nuclei composites. In order to investigate significance of mixed apatite nuclei, cellulose nanofiber-hydroxyapatite composites were fabricated by mixing commercially obtained stoichiometric hydroxyapatite particles with cellulose nanofiber slurry, and the bioactivity was evaluated by using simulated body fluid.

Abstract: We prepared hydroxyapatite (HA) capsules encapsulating maghemite particles. In order to evaluate enzyme immobilization behavior of the HA capsules under alkaline condition, we immobilized five kinds of enzymes with different isoelectric point in carbonate/bicarbonate buffer (CBB, pH 10.0). When the enzymes in CBB were moderately charged, immobilization efficiency on the HA capsules showed the highest value. It was suggested that immobilization efficiency was affected according to both pI of enzyme and pH of the surrounding solution and that enzyme immobilized on the HA capsules by not only electrical double layer interactions but also ion interaction and other interactions.

Abstract: We aimed to clarify the effect of sulfuric acid treatment and oxygen plasma treatment on changes in surface condition of PEEK substrates during fabrication process of bioactive apatite nuclei (AN) precipitated PEEK. We treated PEEK substrate by sulfuric acid treatment. This treatment contributed to provide micropores and sulfo groups on the surface of the PEEK. Next, we treated the PEEK with oxygen plasma at 200 W for 4 minutes. By this treatment, both generation of carboxyl groups and increase of sulfo groups were occurred and significant improvement of hydrophilicity of the surface of the PEEK was occurred. Finally, we precipitated AN on the surface of the PEEK. By this treatment, high apatite-forming ability was achieved.

Abstract: The fabrication of bioactive hydrophobicized cellulose nanofiber consisted of two steps. First, cellulose nanofiber-apatite nuclei composites were prepared by mixing apatite nuclei with cellulose nanofiber slurry and air-drying. Second, the obtained specimens were immersed in alkylketene dimer. By this final treatment, the surface of cellulose nanofiber-apatite nuclei composites could be hydrophobicized. In order to impart apatite-forming ability to the hydrophobicized cellulose nanofiber, the various amount of apatite nuclei were mixed with cellulose nanofiber slurry, and the bioactivity was evaluated by using simulated body fluid.

Abstract: When pH or temperature of simulated body fluid (SBF) is raised, fine particles of calcium phosphate are precipitated. We found that this fine particle actively induces hydroxyapatite from body fluid or SBF and named the particle Apatite Nucleus (AN). In this study, we attached AN on the surface of γ-Fe₂O₃ nanoparticles and soaked them in SBF. By this treatment, hydroxyapatite was induced from AN and covered the whole surface of the γ-Fe₂O₃ nanoparticles, then hydroxyapatite microcapsule encapsulated γ-Fe₂O₃ was fabricated. We dispersed the microcapsules in urease solution, and collected the microcapsules by neodymium magnet. It was indicated that the urease was adsorbed to the hydroxyapatite microcapsules and collected by the magnetism of γ-Fe₂O₃ successfully.

Abstract: Micropores were formed on the surface of polylactic acid (PLA) plate by doubled sandblasting process using alumina particles with 14.0 μm for average particle size as first process, then using the particles with 3.0 μm for average particle size as second process. Apatite Nucleus (AN) was precipitated in the pores. By these treatments, bioactive AN precipitated PLA was fabricated. Bioactivity of the AN precipitated PLA was examined by soaking in SBF and it was observed that hydroxyapatite was induced on the surface of the PLA within 1 d. High adhesive strength of hydroxyapatite layer was achieved due to a mechanical interlocking effect between hydroxyapatite formed in the micropores and the PLA plate.

Abstract: Micropores were formed on the surface of Ti metal, Ti-15Mo-5Zr-3Al alloy, Ti-12Ta-9Nb-3V-6Zr-O alloy plate by doubled sandblasting process using silicon carbide particles with 14.0 μm for average particle size as first process, then using the particles with 3.0 μm for average particle size as second process. Apatite Nuclei (AN) were precipitated in the pores. By these treatments, bioactive AN-precipitated Ti alloys were fabricated. Bioactivity of the AN-precipitated Ti alloys was examined by soaking in SBF and it was observed that hydroxyapatite was induced on the surface of the Ti alloys within 1 d. High adhesive strength of hydroxyapatite layer was achieved due to a mechanical interlocking effect between hydroxyapatite formed in the micropores and the plate.

Abstract: Many micropores were formed on the surface of a Ti-15Mo-5Zr-3Al alloy plate and a polyethylene terephthalate (PET) plate by sandblasting, Apatite Nuclei were precipitated in the pores, then bioactive Apatite Nuclei-precipitated composites were fabricated. In order to examine the bioactivity, the composites were soaked in SBF and it was observed that hydroxyapatite was induced on the whole surface within 1 d. The hydroxyapatite layer possessed high adhesive strength to the plate due to a mechanical interlocking effect between hydroxyapatite in the micropores and the plate.