Papers by Author: Takeshi Yabutsuka

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: In order to improve the corrosion resistance, bioabsorbable magnesium (Mg) alloy was immersed in an aqueous solution with three times of Ca²⁺ and HPO₄^2- in comparison with those of conventional SBF at the moderate temperature. After immersion in the solution, the whole surface of Mg alloy was coated with plate-like crystals consisting of octacalcium phosphate (OCP). Then the OCP-coated Mg alloy was immersed in the alkali solution. Although significant change of morphology was not observed, the OCP formed on the Mg alloy was transformed to hydroxyapatite (HAp) under alkali condition.

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: When the pH or the temperature of a simulated body fluid is raised, fine particles of calcium phosphate are precipitated, which are named apatite nuclei (AN). In this study, we aimed to impart bioactivity to polycaprolactone by incorporating AN. AN-PCL composite films having different weight percentages of AN in PCL were fabricated by solution casting technique, using doctor blade method. Results showed that more than 20 wt.% AN-PCL films were fully covered with hydroxyapatite layer in three days soaking period in SBF.

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: Particles of calcium phosphate were precipitated by raising the temperature and the pH of simulated body fluid (SBF) named Apatite Nuclei (AN). AN and polyvinylidene fluoride (PVDF) composites thin films with different weight percentages of AN in PVDF were fabricated by solution casting technique, using doctor blade method. In order to assess the bioactivity, the thin films were soaked in simulated body fluid (SBF). It was found that the film containing 30 wt.% of AN in PVDF actively induced hydroxyapatite formation in 3 days soaking period in SBF.

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: Bioabsorbable magnesium (Mg) alloy was anodized in 1.0 M NaOH solution. Then the anodized Mg alloy was immersed in an aqueous solution with three times concentration of Ca²⁺ and HPO₄^2- in comparison with those of biological environment to improve its corrosion resistance. The whole surface of Mg alloy was successfully coated with crystalline calcium phosphate (CaP) within 1 day. The CaP coated Mg alloys showed high corrosion resistance in SBF.