Papers by Author: Toshiyuki Ikoma

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Authors: Toru Tonegawa, Toshiyuki Ikoma, Tomohiko Yoshioka, Kazuo Shinozaki, Nobutaka Hanagata, M. Tanaka
Abstract: Insulin delivery carriers using low crystalline porous zinc hydroxyapatite (ZnHAp) microparticles with different crystal sizes and novel formulation method of poly (lactic acid) (PLA) have been developed to achieve the sustained-release of insulin. The adsorption isotherm curves of insulin dissolved into acetic acid of pH4.5 onto ZnHAp nanocrystals show non-Langmuir type due to the dissolution of the ZnHAp microparticles; the adsorption amounts were increased with the increase of crystalline sizes. The PLA formulation, coating the outer layer of microparticles, showed the apparent reduction of initial burst for insulin. The amounts of initial release of insulin decreased with the increase of crystalline sizes of ZnHAp, which could be attributed to the different meso-porous structure depending on its crystal sizes.
Authors: Motohiro Tagaya, Toshiyuki Ikoma, Taro Takemura, Mitsuhiro Okuda, Nobutaka Hanagata, Tomohiko Yoshioka, Dinko Chakarov, B. Kasemo, M. Tanaka
Abstract: The adsorption of multiple proteins derived from fetal bovine serum (FBS) in phosphate buffer saline (PBS) and alpha minimum essential (aMEM) was in situ analyzed with a quartz crystal microbalance with dissipation technique on gold, titanium and HAp sensors. The adsorption behaviors of FBS proteins were varied depending on the sensors. The DD/Df value of the HAp sensor were clearly different in PBS and aMEM, and others were not changed. The viscoelastic properties of the protein films adsorbed on the HAp sensor in PBS were flexible in comparison with those on the gold and titanium sensors. The D-f plots incidated that the proteins adsorbed on HAp in PBS would lead to competitive adsorption and conformational change and those in aMEM could form a monolayer. The adsorption behavior on the HAp in carbonate buffer saline was found to be similar to that in aMEM. These differential adsorption behaviors on the HAp surface were attributed to the pre-adsorptive ion, such PO43- or CO32- in the solvent.
Authors: Kimiyasu Sato, Toshihiro Kogure, Toshiyuki Ikoma, Yuri Kumagai, M. Tanaka
Authors: H. Omi, Soichiro Itoh, Toshiyuki Ikoma, Y. Asou, S. Nishikawa, M. Tanaka, Kenichi Shinomiya, Satoshi Toh
Abstract: Hydroxyapatite/hyaluronic acid (HAp/HyA) and hydroxyapatite/chondroitin sulfate (HAp/ChS) microparticles, which show the high adsorption ability of proteins, high biocompatibility and osteoconductivity, are potential scaffolds for a time-controlled BMP release. The present study evaluated the biocompatibility and osteoconductivity of the composites after injection into bone defect. Drilled bone holes were made at tibia and femur of Japanese white rabbits, and HAp/HyA or HAp/ChS was implanted into each bone hole using an injection syringe. After 2 and 4 weeks of implantation, rabbits were sacrificed and histological observations were conducted with HE, TRAP, and ALP staining. Histological observations revealed that HAp/ChS has superior biocompatibility compared with HAp/HyA, and 20% HAp/ChS promotes bone formation as well as osteoblast activities compared with lower ratios of HAp/ChS.
Authors: Rikako Kino, Toshiyuki Ikoma, Shunji Yunoki, Akira Monkawa, Atsushi Matsuda, Go Kagata, Tetsuo Asakura, Masanobu Munekata, M. Tanaka
Abstract: Silk fibroin (SF) films containing 5wt% of CaCl2 were prepared by a cast-film method from the degummed SF and then immersed into the simulated body fluid (SBF) to deposit hydroxyapatite (HAp) crystals. The multilayer film of HAp and SF (5-layers), and pure SF film (4-layers) were prepared by a thermo-compression method at 130 °C and 3MPa for 4min. The ratio of β-sheet structure against other structures in both samples showed almost same value of 55.8% and 55.1%. The swelling ratio and in vitro biodegradation were examined by incubating in phosphate-buffered saline (PBS) with and without protease XIV for 1 to 14 days. The changes of sample weight and its tensile strength were investigated. The multilayer film showed slower biodegradation and higher mechanical strength compared with pure SF film.
Authors: Xiang Dong Zhu, Hong Song Fan, Chao Yong Zhao, Toshiyuki Ikoma, M. Tanaka, Ji Yong Chen, Xing Dong Zhang
Abstract: Studying on the interaction between proteins and calcium phosphate implants is one of the basic subjects in biomaterials science and engineering. In this work, zeta potentials and contact angles of hydroxyapatite (HA) and biphasic calcium phosphate (BCP) ceramics were measured, and the adsorption behaviors of bovine serum albumin (BSA) on the surfaces were investigated. The adsorption isotherms of BSA on both ceramics follow the Langmuir type, however, BCP shows higher BSA adsorption ability. The differences of contact angles and zeta potentials in HA and BCP are the key factors to determine their ability to bind BSA molecules.
Authors: Toru Tonegawa, Toshiyuki Ikoma, Tomohiko Yoshioka, Guo Ping Chen, Nobutaka Hanagata, M. Tanaka
Abstract: The adsorption properties of metal ions containing hydroxyapatite (Ca10(PO4)6(OH)2, HAp) were elucidated for the development of protein drug carrier. As-prepared metal ion containing HAp nanocrystal showed plate-like morphology with 10-20nm in length and 5-10nm in width. The metal ion containing HAp microparticles had higher specific surface area than the HAp microparticle. The adsorption amount per unit area of HAp showed higher than those of metal ion containing HAp. The adsorption behavior followed the Langmuir curves for each protein, indicating the monolayer adsorption. The loaded amount of proteins could be one of the most important properties for the application of drug delivery carrier.
Authors: Toru Tonegawa, Toshiyuki Ikoma, Guo Ping Chen, M. Tanaka
Abstract: Control of protein release without the initial burst from zinc containing hydroxyapatite porous microparticles (Zn-HAp) was investigated with a novel formulation method. The formulation method was a coat of polyL(L-lactide; PLA) on the microparticle with nano-thickness, which obviously suppressed the initial burst of protein release compared with the microparticles without the formulation, the coat of PLA. The HAp/PLA microparticle with 1-20μm of the size distribution was available for the drug delivery carrier of proteins without the degradation.
Authors: Taro Takemura, Toshiyuki Ikoma, Nobutaka Hanagata
Abstract: Surfaces of sintered hydroxyapatite (HAp) were treated with four kinds of acids, hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4) and hydrogen peroxide (H2O2). On these acid-treated HAp surfaces, osteoblast-like MC3T3-E1 cells were cultured for 20 days. The matrix mineralization was observed in HCl-treated HAp and HNO3-treated HAp, but not in non-treated HAp, H2SO4-treated HAp and H2O2-treated HAp. Gene expressions of Bglap2 encoding osteocalcin and Akp2 encoding alkaline phosphatase were higher in HCl-treated HAp and HNO3-treated HAp than those in the others. These results indicate that not only hydrochloric acid but also nitric acid improves performance of HAp to mature osteoblast.
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