In the present study new calcium sulfate-based nanocomposite bone cement with improved physicochemical and biological properties was developed. The powder component of the cement consists of 60 wt% α-calcium sulfate hemihydrate and 40 wt% biomimetically synthesized apatite, while the liquid component consists of an aqueous colloidal silica suspension (20 wt%). In this study, the above mentioned powder phase was mixed with distilled water to prepare a calcium sulfate/nanoapatite composite without any additive. Structural properties, setting time, compressive strength, in vitro bioactivity and cellular properties of the cements were investigated by appropriate techniques. From X-ray diffractometer analysis, except gypsum and apatite, no further phases were found in both silica-containing and silica-free cements. The results showed that both setting time and compressive strength of the calcium sulfate/nanoapatite cement improved by using colloidal silica suspension as cement liquid. Meanwhile, the condensed phase produced from the polymerization process of colloidal silica filled the micropores of the microstructure and covered rodlike gypsum crystals and thus controlled cement disintegration in simulated body fluid. Additionally, formation of apatite layer was favored on the surfaces of the new cement while no apatite precipitation was observed for the cement prepared by distilled water. In this study, it was also revealed that the number of viable osteosarcoma cells cultured with extracts of both cements were comparable, while silica-containing cement increased alkaline phosphatase activity of the cells. These results suggest that the developed cement may be a suitable bone filling material after well passing of the corresponding in vivo tests.
In this study, bioceramic nanocomposites were synthesized by sintering compacted bodies of hydroxyapatite (HA) mixed with 5 or 15 wt% nanosilicon carbide at 1,100 or 1,200 degrees C in a reducing atmosphere. Pure hydroxyapatite was also prepared for comparison. Phase compositions, structural and physical properties of the composites were studied using appropriate techniques. Some in vitro biological properties of the composites were also investigated by using newrat calvaria osteoblastic cells. X-ray diffraction analysis indicated that tricalcium phosphate (TCP) comprising negligible alpha-TCP and considerable beta-TCP were formed in composites during sintering meanwhile hydroxyapatite and silicon carbide (SiC) were also existed in the composition. Based on the results, that composite made of 5 wt% nanosilicon carbide exhibited higher bending strength, fracture toughness and bulk density than pure HA and composite with 15 wt% silicon carbide. The scanning electron microscopy coupled with energy dispersive X-ray analysis revealed that the addition of nanosilicon carbide suppressed the grain growth and yielded a feature of island-type clusters consisting of blistered calcium phosphate (HA and TCP) and SiC grains. Also, in this study, better proliferation rate and alkaline phosphatase activity were observed for the osteoblastic cells seeded on top of the composites compared to pure HA. Overall, the results indicated that the composite of 95 wt% hydroxyapatite and 5 wt% SiC exhibited better mechanical and biological properties than pure HA and further addition of SiC failed strength and toughness.
In this study, calcium phosphate cements (CPCs) were prepared by using hyaluronic acid (HA) solutions with two different molecular weights. The physical, physicochemical and structural properties of these cements were characterised and compared with those of conventional CPC as control group. Results revealed that the long setting time and the low compressive strength of the CPC could be improved drastically by using HA in the cement composition, in a molecular weight dependent manner. The HA polymer has also a promising effect on cement injectability, which is more considerable in high molecular weight HA. The X-ray diffraction patterns of set cements showed that, in both control group and HA containing cements, primary reactant components were completely converted to nanostructured apatite after soaking in simulated body fluid. This study suggests that calcium phosphate nanocomposite cement obtained by HA solution can be successfully used as injectable bone filler material.
Indole derivatives R 0140 Oxalic Acid Dihydrate: A Reusable and Cost-Effective Catalyst for the Synthesis of Bis(indolyl)methanes under Solvent-Free Conditions. -The efficient, mild, and eco-friendly method includes electrophilic substitution reaction of indole derivatives with aldehydes or ketones. -(DABIRI*, M.; BAGHBANZADEH, M.; AZIMI, S. C.; AHMADZADEH-ASL, S.; ARDESTANI, R. R.; Lett. Org. Chem. 5 (2008) 6, 490-494; Dep. Chem., Shahid Beheshti Univ., Evin 19839, Tehran, Iran; Eng.) -H. Toeppel 51-116
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