Atsushi Yamazaki

Fibronectin-calcium phosphate composite layer on hydroxyapatite to enhance adhesion, cell spread and osteogenic differentiation of human mesenchymal stem cells in vitro

Fibronectin (Fn) and type I collagen (Col) were immobilized on a surface of a hydroxyapatite (HAP) ceramic by coprecipitation with calcium phosphate in a supersaturated calcium phosphate solution prepared by mixing clinically approved infusion fluids. These proteins and the calcium phosphate precipitate formed a composite surface layer. As a result, the proteins were immobilized firmly as not to be released completely for 3 d in a physiological salt solution. When human mesenchymal stem cells (hMSCs) were cultured on a HAP ceramic in a differentiation medium supplemented with dexamethasone, beta-glycerophosphate and ascorbic acid, hMSCs spread well within 1 h. The alkaline phosphatase (ALP) activity of hMSCs cultured on the Fn-calcium phosphate composite layer significantly increased compared with that of hMSCs cultured on the untreated HAP ceramic. On the other hand, Col did not increase the ALP activity of hMSCs and no synergy between Fn and Col was observed. Therefore, the Fn-calcium phosphate composite layer formed on the HAP is useful for the enhancement of the spreading and osteogenic differentiation of hMSCs in vitro.

Model calculation of sepiolite surface areas

In general, the N2-BET surface areas of sepiolite samples range from 95 to 400 m2/g depending on deposits.The surface areas of five sepiolites, all varying in crystallite size, were measured on heating, and were compared with a model calculation. A sharp decrease in the surface area, due to crystal folding, was observed between 200° and 400°C. Both before and after the folding, each sepiolite sample had peculiar values. Our model sufficiently explains this difference in surface areas among the samples. In the model, which is based on the Brauner-Preisinger structural model, surface area is a function of the crystallite size and the ratios of the coverage for nitrogen adsorption on both the internal and external surfaces. These ratios of the coverage can be inversely estimated from the model. The ratios of the coverage on the internal surface are less than 0.19, and that on the external surface between 0.7 and 1.0.

Application of hydroxyapatite-sol as drug carrier

The application of hydroxyapatite-sol as a drug carrier is being developed. Hydroxyapatite-sol which is a suspension consisting of hydroxyapatite nano-crystals, was synthesized using an ultrasonic homogenizer. The size of the crystals was 40 x 15 x 10 mm3 on average and their specific surface area was 100 m2/g. An amount of a glycoside antibiotics adsorbed onto hydroxyapatite nano-crystals was measured. The drug adsorbed 0.2 mg per 1 mg of hydroxyapatite. The affect of the drug adsorbed onto the hydroxyapatite was investigated using cancer cells. The drug, adsorbed onto the hydroxyapatite nano-crystals, inhibited cancer cell growth.

Photocatalytic Property and Deep Levels of Nb-doped Anatase TiO2 Film Grown by Metalorganic Chemical Vapor Depostion

A Nb-doped anatase TiO2 (Nb: 5 at%) film was grown on a SrTiO3(001) substrate by metalorganic chemical vapor deposition. Deep level transient spectroscopy analysis revealed that this film possessed two kinds of deep levels due to the Nb ions, which were found to exist at 0.32 eV and 0.67 eV below the bottom of the conduction band. The photocatalytic activity of this film was low compared with that of the undoped anatase film, suggesting that the deep levels acted as recombination centers of photoexcited electron-hole pairs.

Dissolution rate of zinc-containing β-tricalcium phosphate ceramics

The dissolution rates of ceramic tricalcium phosphate (TCP) and zinc-containing tricalcium phosphate (ZnTCP) ceramics at pH 5.5 decrease with increasing zinc content. The relative dissolution rates of ceramic ZnTCP with zinc contents of 0.5 and 1.0 mol% are more than three times higher than the relative resorbed volumes of these ZnTCP ceramics which were reported previously. The dissolution rates are likely controlled by only one mechanism, that is polynucleation, in the zinc content range from 0 to 1.0 mol%. Since the surface area of ceramic TCP or ZnTCP is much lower than that of powdered TCP or ZnTCP, the initial dissolution flux of ceramic TCP or ZnTCP remains unchanged for a longer period than that of powdered TCP. As a result, no change in dissolution kinetics is expected during one cycle of osteoclastic resorption. Since neither the dissolution rate nor the change in dissolution kinetics accounts for the previously reported drastic reduction in osteoclastic resorption associated with ZnTCP, it is concluded that the drastic reduction in resorption arises from the suppressive effects of ZnTCP on osteoclast formation or osteoclastic activity.

Pulse mode effects on crystallization temperature of titanium dioxide films in pulse magnetron sputtering

Pulse mode effects on the crystallization temperature and photocatalytic properties of TiO 2 films were investigated. TiO 2 films were deposited on silica glass substrates using a pulse magnetron sputtering apparatus in the unipolar and the bipolar pulse modes. X-Ray diffraction showed that in the bipolar pulse mode the rutile phase TiO 2 film grew at lower substrate temperature compared with the unipolar pulse mode. The photocatalytic activities obtained from the photoreduction of Ag ions at the surface of TiO 2 films indicated that the anatase phase TiO 2 films grown in the bipolar pulse mode had higher photocatalytic activity compared with those grown in the unipolar pulse mode. This suggests that the bipolar pulse mode is an effective technique to achieve higher nhotocatalytic activity of TiO 2 film.

Thermal analysis of ground dolomites

Abstract The characteristics of ground dolomites which have undergone a change in crystal structure and of those almost free from structural change, were studied mainly by thermal analysis. Firstly, pulverized samples passed through a 325-mesh Tyler sieve were ground further for 1, 2, 3, 5 and 24 h in order to observe their change with progressive grinding. The X-ray diffraction (XRD) and IR patterns and TG-DTA curves obtained in flowing 100% CO 2 gas indicated a gradual loss of the cation ordering characteristic of dolomite structure up to a grinding period of 24 h when a new phase of lower ordering appeared; this confirmed the results of earlier investigators. To characterize further the gradually developing new phase which was not apparently distinguished by XRD or IR analysis, TG-DTA curves were obtained under varying CO 2 partial pressures. It was found that the new phase decomposed in a straightforward manner, similarly to that of magnesite and quite differently from that dolomite, its decomposition temperature and rate were dependent upon the CO 2 partial pressure. In addition, the influence of grain size and particle size distribution on the temperature and shape of the endothermic peak of the DTA curve was studied. It was found that the peak shape is affected by the grain size, and moreover that the temperature range of the endothermic peak is affected by the size and, more importantly, the size distribution of the particles.

Hollow Structure Improved Anti-Cancer Immunity of Mesoporous Silica Nanospheres In Vivo.

Hollow and non-hollow mesoporous silica nanospheres are synthesized and used for cancer vaccine adjuvants. The hollow structure of mesoporous silica nanospheres significantly promote cellular uptake of a model cancer antigen by macrophage-like cells in vitro, improve anti-cancer immunity, CD4(+) and CD8(+) T cell populations in splenocytes of mice in vivo.

Deep Level Transient Spectroscopy Analysis of an Anatase Epitaxial Film Grown by Metal Organic Chemical Vapor Deposition

The deep level transient spectroscopy (DLTS) study of anatase-type TiO2 material was performed for the first time. The anatase film was epitaxialy grown on a conductive Nb-doped single-crystalline SrTiO3 (100) substrate by metal organic chemical vapor deposition. The photoluminescence characteristics of this anatase film were identical to those in previous reports, where they were attributed to the radiative recombination of self-trapped excitons. According to the DLTS analysis, it was revealed that this anatase film had a characteristic deep level located at 0.96 eV below the bottom of the conduction band with large concentration (6.5×1016/cm3) and capture cross section (8.3×10-13 cm2). Since the capture cross section of this level appeared to be too large to be caused by point defects, the origin of this deep level was attributed to line defects such as dislocations.

Control of gene transfer on a DNA-fibronectin-apatite composite layer by the incorporation of carbonate and fluoride ions.

Gene transfer techniques are useful tools for controlling cell behavior, such as proliferation and differentiation. We have recently developed an efficient area-specific gene transfer system using a DNA-fibronectin-apatite composite layer (DF-Ap layer). In this system, partial dissolution of the composite layer is likely to be a crucial step for gene transfer. In the present study, layer solubility was adjusted by incorporating various contents of carbonate or fluoride ions into the DF-Ap layer via ionic substitution for the apatite crystals. Carbonate ion incorporation increased the solubility of the DF-Ap layer, thereby increasing the efficiency of gene transfer on the layer. In contrast, the incorporation of fluoride ions decreased the solubility of the DF-Ap layer, thereby decreasing the efficiency and delaying the timing of gene transfer on the layer dose-dependently. The present gene transfer system with controllable efficiency and timing would be useful in tissue engineering applications because cell differentiation can be induced effectively by regulating appropriate gene expression with suitable timing.