Papers by Author: Kimihiro Yamashita

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Authors: Reiko Kato, Satoshi Nakamura, Keiichi Katayama, Kimihiro Yamashita
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Authors: Takashi Kizuki, Masataka Ohgaki, Kimihiro Yamashita, Yoshiyuki Yokogawa
Abstract: Autograft, allograft, and biomaterials had been developed for bone regeneration. In recent year, a tissue engineering technique has been paid much attention for next generation implant. A problem of bone tissue engineering to be solved is a development of the substrate that is suitable for cell adhesion, proliferation, and differentiation. A biomimic scaffold for tissue culture was proposed, and then a cell response on the scaffold was estimated. The scaffold composed by a calcium deficient apatite with an adsorbed serum protein was formed on a ceramic hydroxyapatite (HAp) and surface-modified titanium by a soaking in cell-culture medium supplemented with fetal bovine serum. Excellent results on cell proliferation and cell adhesion were obtained only on osteoblast-like cells (MC3T3-E1). An actin filament in narrow filopodium of the spindle-shaped MC3T3-E1 cells on the ceramic HAp had a regular course. On the other hand, ends of the actin filament of the widely spread cells on the apatite layer with serum protein were scattering. It was suggested that the scattering of the actin end showed an existence of fibronectin, and then tight adhesion would be obtained by the many focal adhesion. Accordingly, the effectiveness of the biomimic scaffold containing serum protein on cell growth was confirmed.
611
Authors: Masahiro Tsukamoto, Togo Shinonaga, Akiko Nagai, Kimihiro Yamashita, Takao Hanawa, Nobuhiro Matsushita, Guo Qiang Xie, Nobuyuki Abe
Abstract: Titanium (Ti) is one of the most widely used for biomaterials, because of its excellent anti-corrosion and high mechanical properties. In addion to these properies, the bioactivity of Ti is required. Recently, coating of the titanium dioxide (TiO2) film on Ti plate surface is useful methods to obtain biocompatibility of Ti plate. If periodic nanostructures were formed on the film surface, direction of cell spreading might be controlled due to grooves direction. Then, femtosecond laser is one of the useful tools of periodic nanostructures formation. Peiriod of periodic nanostructures might be varied by changing the laser wavelength. In the experiments, the film was formed on Ti plate with an aerosol beam which was composed of submicron size TiO2 particles and helium gas. The film was irradiated with the femtosecond laser. Laser wavelengths of the laser was at 1044, 775 and 388 nm, respectively. Periodic nanostructures, lying perpendicular to the laser electric field polarization vector, were formed on the film by femtosecond laser irradiation at 1044, 775 and 388 nm, respectively. The period of the periodic nanostructures on the film produced by femtosecond laser irradiation at 1044, 775 and 388 nm was about 350, 230 and 130 nm, respectively. In the cell test, cell spreading along the grooves of the periodic nanostructures was observed although it was not done for the film without the periodic nanostructures. These results suggested that direction of cell spreading could be controlled by the periodic nanostructures formation
1377
Authors: Shun-ichi Nakamura, Kimihiro Yamashita
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Authors: Shigeki Kishi, Norikazu Okimoto, Satoshi Nakamura, Keishi Nishio, Kazuaki Hashimoto, Yoshitomo Toda, Kimihiro Yamashita
Abstract: To produce ceramics with high mechanical strength and bioactivity, we developed the little amount of nano-sized hydroxyapatite (HA)-doped zirconia composite ceramics (nanoHA-Z). The bioactivity of the nanoHA-Z was studied by in vitro estimation with simulated body fluid (SBF). Scanning electron microscopy observation showed deposited bone-like apatite layer entire covering the surface of nanoHA-Z ceramics in SBF. The enhanced apatite formability was attributed to higher Ca and PO4 concentrations in the vicinities of the nanoHA-Z surfaces due to the dissolution of the β-tricalcium phosphate decomposed from the added HA. Utilization of Chemicovector effect was proved to be one of the powerful approaches for improvement method of biomaterials.
589
Authors: Natalie Ohashi, Miho Nakamura, Akiko Nagai, Yumi Tanaka, Yasutaka Sekijima, Kimihiro Yamashita
Abstract: Various bioactive calcium phosphates such as hydroxyapatite (HA) and carbonate apatite (CA) bone substitutes have been studied because of the biocompatibility and osteoconductivity when implanted into bone defects. In this study, the interaction between bioceramics and osteoclast-like cell using the cell-line such a RAW264 was examined for the investigation of the important factors of the osteoclastic responses. From the results, the possibility of effectiveness by surface geometry and chemical property means solubility was suggested. Moreover, it was considerable that the CA induced much stronger responses to osteoclast-like cells than the HA.
1039
Authors: Satoshi Nakamura, M. Ueshima, Takayuki Kobayashi, Kimihiro Yamashita
445
Authors: Jun Ichi Hamagami, Atsushi Goto, Takao Umegaki, Kimihiro Yamashita
149
Authors: H. Takeda, Satoshi Nakamura, Kazumasa Yamada, Toshio Tsuchiya, Kimihiro Yamashita
35
Authors: Naohiro Horiuchi, Miho Nakamura, Akiko Nagai, Kimihiro Yamashita
Abstract: Calcium phosphate powders (hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, and tetracalcium phosphate) were electrically polarized by an applied dc voltage. Thermally stimulated depolarization current measurements confirmed that each calcium phosphate powder exhibited surface charges after polarization treatment. The surface adsorption of simvastatin on each powder was investigated. We observed a difference in adsorption between polarized and non-polarized powders. This difference in adsorption is due to the electrostatic force between the polarized surface and the open-ring form of simvastatin, which has a larger electrical polarity than its closed-ring form.
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