Papers by Keyword: Vaterite

Abstract: Cellular activities of human mesenchymal stem cells (MSCs) and osteoblasts (HOBs) on a silicon-releasable scaffold, which is siloxane-doped poly(lactic acid) / vaterite composite coated with hydroxycarbonate apatite (SPV-H), were estimated using two types of media, with or without organic factors, dexamethasone (Dex) and β-glycerophosphate (β-GP). The culture tests using MSCs shows that the level of alkaline phosphatase (ALP) activity in the cells cultured on SPV-H increased for 21-day culturing in medium without Dex and β-GP. The proliferation of MSCs on SPV-H was significantly higher than that on a poly(lactic acid) / vaterite composite coated with hydroxyapatite (PV-H) at all time points. In the case of supplementing Dex and β-GP to the medium, the level of ALP activity in MSCs cultured on SPV-H was higher in comparison with that on PV-H at all time points. Scanning electron microscopy showed that there were some agglomerates in HOBs cultured on the SPV-H surface after 21-day culturing in the medium without the factors, while there are no agglomerates on PV-H. The agglomerates were regarded from laser Raman spectroscopy as bone nodules. This result implies stimulation to HOBs by silicon species in SPV-H. SPV-H is expected to be useful as the scaffold for bone tissue engineering.

Abstract: A silicon-containing apatite layer was prepared on a metallic titanium substrate coated with a silica layer. The silica layer on a titanium substrate was derived from water glass through heat-treatment at 300 °C for 2 hr and subsequent acid-treatment using 0.1 N-HCl at 50 °C for 2 hr. The silica layer was homogeneously coated with nano-sized vaterite powders (~ 0.5 μm in diameter). The vaterite coating was achieved by utilizing the interaction of surface potentials between the positively charged vaterite and the negatively charged silica layer. After soaking the sample in simulated body fluid at 37 °C for 3 days, hydroxyapatite (HA) formed on the surface of the silica-coated titanium. The HA layer was found to include a trace amount of releasable silicon, which may enhance the osteoblast proliferation.

Abstract: Mercapto group controls the adsorption and release of insulin, which is one of the proteins for enhancing the osteoblast proliferation. Silicon-ion-species were reported to stimulate the bone-forming ability of osteoblasts. The present paper describes doping with mercapto groups and silicon-ion-species in a calcium carbonate/poly (lactic acid) composite membrane, which is prepared by a sol-gel method using 3-mercaptopropyltrimethoxysilane. The membrane was amorphous and showed high flexibility. A quantitative analysis by thiol-disulfide exchange reaction using 2, 2-dipyridyl disulfide reagent showed that the amount of mercapto group existing on membrane surface was estimated to be about 5.51μmol/cm2. A trace amount of silicon-ion-species was released from the membrane after soaking in tris (hydroxymethyl) aminomethane buffer solution at 37 oC. The membrane is expected to have high bone-forming ability.

Abstract: Hollow calcium carbonate (CaCO3) particles were synthesized by bubbling CO2 in the solution of calcium chloride (CaCl2) with the presence of ammonia at room temperature. In this method, CO2 bubble, besides as reactant, has an important role as a template for forming hollow particles. The precipitation was carried out by controlling the precipitation condition, such as pH, flow rate and additives. Hollow calcium carbonate particles were precipitated with the major crystal phase of vaterite. An interesting finding is that magnesium ion (Mg2+) can suppress the transformation of vaterite to calcite by inhibiting the growth of the calcite.

Abstract: Hollow calcium carbonate (CaCO3) particles were synthesized by bubbling CO2 in the solution of calcium chloride (CaCl2) with the presence of ammonia at room temperature. Hollow calcium carbonate is a potential component to be used as pharmaceuticals, agrochemicals, and catalysis. This paper investigated the effect of additive on the hollow structure. In this study was used vanadate ion as additive agent. Physical characteristics of precipitate were evaluated using scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Abstract: Hydroxycarbonate apatite (HCA), which formed on a poly(lactic acid) (PLA) composite membrane containing vaterite or calcium chloride after soaking in simulated body fluid, was examined to clarify the importance of the ceramic phases in the composites. FT-IR spectra showed that the ratio of CO3/PO4 in the infrared adsorption bands of HCA formed on the PLA composite containing vaterite was much larger than that of HCA formed on the PLA composite containing calcium chloride. Substitution of carbonate ion in hydroxyapatite is believed to be strongly influenced by ceramic phases in the composites. The zeta potentials of HCA formed on the PLA composite containing vaterite or calcium chloride was -6 mV or -17 mV, respectively. The zeta potential may be influenced by the amount of carbonate ion in hydroxyapatite.