Papers by Author: Akiyoshi Osaka

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: A bioactive composite coating consisting of one layer of titania and one layer of apatite was formed on Ti substrate. The first layer of crystalline titania was deposited on Ti at low temperatures either through oxidation of Ti by hydrogen peroxide solution or through hydrolysis of TiF4 or TiCl4 solution. It was shown that the crystalline titania, either in the form of anatase or rutile, induced formation of the second layer of apatite in a simulated body fluid. However, the trace elements in the titania layer affected greatly apatite formation. The Cl incorporated in the titania layer did not hinder apatite formation while F did. The two-layer composite coating should enhance bonding of Ti implants to bone tissue.

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: Heating reduces the amount of Ti-OH groups in the surface layers that are considered to favor apatite nucleation. Thus, low temperature processes are developed to fabricate bioactive titania. Anatase/rutile dual layers were deposited on titanium substrates when they were soaked in TiOSO4/H2O2 solution at low temperature, and than aged in hot water, which can induce apatite formation in DMEM. The resulted titania layers have apatite-forming ability. The organic molecules in DMEM medium had reduced the apatite formation on as-treated substrates in some measure.