Papers by Author: Satoshi Hayakawa

Abstract: Apatite formation on the surface of materials in body environment is an essential condition to show osteoconduction after implantation in bony defects. This study reports the novel technique for providing the apatite-forming ability to titanium metals by only controlling the spatial gap and thermal oxidation. Two pieces of titanium thermally oxidized at 400 °C were set together like V-letter with varied mouth opening. They showed the formation of apatite on both facing surface after exposure to a simulated body fluid (SBF) proposed by Kokubo and his colleagues, when the gap was less than approximately 600 μm. Moreover, specimens with micro-grooves of 500 μm in depth and 200-1000 μm in width was able to form apatite in SBF with in 7 days, after they were thermally oxidized at 400 oC. These results indicated that the titanium metals were provided with apatite-forming ability, i.e. osteoconduction, due to controlled gap with thermally oxidized surface. Hence, we conclude that bioactive titanium substrate showing osteoconduction can be produced by designed machining followed by thermal oxidation at an appropriate temperature.

Abstract: Novel hybrid gels in the system gelatin-GPTMS-TEOS were prepared via a sol-gel route, and their ability to release Si(IV) was examined using MG63 osteoblast-like cell culture. The amount of Si released and the release rate were controllable by changing the mixing ratio of GPTMS and TEOS. In addition, the hybrids had biocompatible surfaces. It is expected that the hybrids will be utilized for the investigation of the effect of Si on cell differentiation and tissue regeneration.

Abstract: Porous chitosan-silicate hybrids were prepared by freeze-drying the precursor sol solutions synthesized from chitosan and 3-glycidoxypropyltrimethoxysilane (GPTMS). Degradability of and the release of cytochrome C in to phosphate buffer saline solution (PBS) were examined as a function of the GPTMS content. The hybrids were less degradable with larger GPTMS contents, and the cytochrome C release profile was so controllable as to give either burst release or slow one due to the GPTMS content. Thus, the present porous chitosan-silicate hybrids were considered applicable to drug delivery systems.

Abstract: Boron-containing hydroxyapatite (BHAp) particles were synthesized by the wet chemical processing method and subsequent thermal treatment at the temperature ranging from 700-1200°C, and examined the effect of boron introduction on the microstructure of BHAp. The local structure around boron and phosphorus in the BHAp was analyzed by solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The heat-treatment above 700°C induced the thermal decomposition of HAp to β-TCP and then the chemical reaction between HAp and B(OH)3 was induced above 900°C, resulting in the formation of boron-substituted HAp particles accompanied by the formation of β-TCP and its transformation to α-TCP above 1200°C.

Abstract: Hydroxyapatite (HAp) and Si-containing hydroxyapatite (SiHAp) particles were synthesized by a wet chemical method. Local structures around Si, P and H in the hydroxyapatites were analyzed by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy. In vitro solubility of those SiHAp particles was evaluated by soaking them in acetic acid/acetate buffer solution (pH=4.0) at 36.5°C. As the Si content increased, the in vitro solubility of the SiHAp particles increased, while their crystallite size changed little.

Abstract: Nano-crystalline Mg-containing hydroxyapatite (Mg·HAp) were prepared by a wet chemical method, for which selective adsorption of proteins was examined, taking bovine serum albumin (BSA) and a pathogenic protein β2-microglobulin (β2-MG) as the model proteins. Increase in the Mg content led to smaller crystallites and larger specific surface area (SA) of Mg·HAps as well as zeta potential, while the amount both of BSA and β2-MG adsorption on Mg·HAp particles. It is thus concluded that the adsorption of BSA and β2-MG on Mg•HAp was associated with surface charges.

Abstract: Rutile films were deposited on poly-l-lactide (PLLA) substrates using 0.5 M titanium tetrachloride aqueous solution at 40 °C for 72 h. The rutile films exhibited excellent in vitro bioactivity as they induced apatite deposition in a simulated body fluid (SBF) within 3 days. This simple treatment provided an effective route to synthesize bioactive and biodegradable scaffolds.

Abstract: Rutile films were deposited on polyethylene terephatalate (PET), polytetrafluoroethylene (PTFE), Silicone, poly6-caprolactam (Nylon6), polyhexamethylene adipamide (Nylon6,6) and Nylon fiber substrates using 0.03 M TiOSO4 and 0.03 M H2O2 aqueous solution at 80°C for 24 h. The rutile films exhibited excellent in vitro bioactivity as they induced apatite deposition in a simulated body fluid (SBF).

Abstract: Titania films were coated by means of sol-gel method on various substrates such as titanium, titanium alloy, silicon wafer, stainless-steel, alumina, and glass slide where they coded as C5Ti, C5Ti6Al4V, C5Si, C5SUS, C5Al2O3 and C5GS, respectively. Their in vitro apatite-forming ability was examined with the Kokubo’s simulated body fluid (SBF; pH 7.4, 36.5°C). C5Ti, C5Ti6Al4V and C5Si deposited apatite particles on their surface within 7 days, whereas, C5SUS, C5Al2O3 and C5GS did not. These results implied that the in vitro apatite-forming ability of the titania films indirectly depended on the chemical or physical properties of the substrates.