Papers by Author: Toshiki Miyazaki

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Authors: Toshiki Miyazaki, Chikara Ohtsuki, Masao Tanihara, Masahiro Ashizuka
545
Authors: Caihong You, Toshiki Miyazaki, Eiichi Ishida, Masahiro Ashizuka, Chikara Ohtsuki, Masao Tanihara
Abstract: Organic polymers with ability of apatite formation in body environment are expected as novel bone substitutes having not only bone-bonding ability, i.e. bioactivity, but also mechanical performance analogous to natural bone. Several metal oxides have been found to be effective for the apatite deposition in body environment. In addition, release of calcium ions from the materials significantly enhances it. In this study, we attempted to synthesize bioactive organic-inorganic hybrids from Poly(vinyl alcohol) (PVA) by incorporation of various metal oxides and calcium salt. Silica and molybdenum oxides were selected as metal oxides. Ability of apatite formation on the hybrids was examined in vitro using simulated body fluid (SBF, Kokubo solution). Apatite deposition were observed to occur on the surfaces of PVA/silica and PVA/molybdenum oxide hybrids in SBF, when their compositions were appropriately controlled.
469
Authors: Takahiro Kawai, Chikara Ohtsuki, Masanobu Kamitakahara, Masao Tanihara, Toshiki Miyazaki, Yoshimitsu Sakaguchi, Shigeji Konagaya
Abstract: Organic polymer coated with hydroxyapatite (so-called apatite) on its surface is a candidate of new hybrid materials for medical applications since it is expected to show bone-bonding ability and achieve mechanical properties derived from organic substrate. We have shown that some kinds of polyamide films containing carboxyl group or sulfonic group form hydroxyapatite in the simulated body environment, when they are incorporated with calcium chloride. In the present study, the polyamide containing carboxyl groups were modified with silanol groups and its apatite-forming ability was investigated in 1.5SBF, which has ion concentrations 1.5 times those of a simulated body fluid (SBF). It was found that polyamide films modified with silanol groups showed higher ability to induce apatite on its surface in 1.5SBF than the films without the modification, when they were incorporated with calcium chloride.
505
Authors: Toshiki Miyazaki, Y. Akioka, Chikara Ohtsuki, Masao Tanihara, J. Nakao, Yoshimitsu Sakaguchi, Shigeji Konagaya
133
Authors: Toshiki Miyazaki, Chikara Ohtsuki, Shinichi Ogata, Masahiro Ashizuka
Abstract: Organic-inorganic hybrids composed of organic polymer and apatite is quite attractive as novel bone-repairing materials since it has mechanical performance analogous to those of natural bone as well as bone-bonding ability, i.e. bioactivity. To fabricate such an apatite-polymer hybrid, biomimetic process has been recently paid much attention. In this process, bone-like apatite is deposited on the surfaces of organic substrates in simulated body fluid (SBF, Kokubo solution) having ion concentrations analogous to those of human extracellular fluid or more concentrated solutions. Previous studies showed that the apatite deposition is triggered by a catalytic effect of carboxyl groups (COOH) on the surfaces of the organic substrates. In this study, we examined apatite deposition on natural polypeptides derived from crops in a biomimetic solution. We selected gluten derived from wheat and zein derived from corn. Both of gluten and zein formed bone-like apatite on their surfaces in a solution that has inorganic ion concentrations 1.5 times those of simulated body fluid, when they were treated with 1 mol/L calcium chloride solution. High content of acidic amino acids such as glutamic acid and aspartic acid in gluten and zein would give large amount of carboxyl groups effective for the apatite nucleation.
671
Authors: Akari Takeuchi, Chikara Ohtsuki, Masanobu Kamitakahara, Shinichi Ogata, Masao Tanihara, Toshiki Miyazaki, Masao Yamazaki, Yoshiaki Furutani, Hisao Kinoshita
403
Authors: Tomohiro Uchino, Chikara Ohtsuki, Masanobu Kamitakahara, Masao Tanihara, Toshiki Miyazaki
Abstract: Apatite formation behavior of tricalcium phosphate (TCP) ceramics with different phases and porosity was investigated in a simulated body fluid (SBF, Kokubo solution). The pure α-TCP with 80% porosity did not form hydroxyapatite (HAp) on its surface after soaking in SBF for 7 days. On the other hand, the pure α-TCP with 20% porosity formed HAp on its surface after soaking in SBF within 7 days, and the biphasic TCP, which consisted of mixture of α-TCP and β-TCP and had 20% porosity, formed HAp within 1 day. The low porosity and coexistence of α-TCP and β-TCP phases in TCP ceramics were effective for apatite formation in SBF.
251
Authors: Toshiki Miyazaki, Moriyoshi Imamura, Eiichi Ishida, Masahiro Ashizuka, Chikara Ohtsuki, Masao Tanihara
Abstract: Apatite formation in living body is essential condition for artificial materials to exhibit bone-bonding ability, i.e. bioactivity. It has been recently revealed that sulfonic group triggers apatite nucleation in body environment. Organic-inorganic hybrids consisting of organic polymer and the sulfonic group are therefore expected to be useful for novel bone-repairing materials exhibiting flexibility as well as bioactivity. In the present study, organic-inorganic hybrids were prepared from vinylsulfonic acid sodium salt and hydroxyethylmethacrylate (HEMA), a kind of acrylic polymer. Bioactivity of the hybrids was assessed in vitro by examining their acceptance of apatite formation in simulated body fluid (SBF, Kokubo solution). The obtained hybrids showed the apatite deposition after soaking in SBF within 7 d.
725
Authors: Takahiro Kawai, Toshiki Miyazaki, Chikara Ohtsuki, Masao Tanihara, J. Nakao, Yoshimitsu Sakaguchi, Shigeji Konagaya
59
Authors: Akari Takeuchi, Chikara Ohtsuki, Toshiki Miyazaki, Shinichi Ogata, Masao Tanihara, H. Tanaka, Yoshiaki Furutani, Hisao Kinoshita
31
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