Modulation of zinc release from bioactive sol-gel derived SiO < inf> 2 -CaO-ZnO glasses and ceramics

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Zinc is an essential trace element which may be effective in promoting hard tissue healing. Glasses in the SiO2-CaO-ZnO system were synthesized via sol-gel methods. Using a constant silica content (70 mol %), the ratio of Ca to Zn was varied (1.5, 3.5, or 6.5), as was the stabilization temperature (650, 750, or 850°C), to examine such effects on the bioactive response and zinc release in simulated body fluid (SBF). XRD revealed the development of CaSiO3 and Ca2ZnSi2O7 crystalline phases during stabilization at 850°C only. N2 adsorption analysis determined that the specific surface area (BET) varied between 14 and 179 m2/g and was dependent on composition and stabilization temperature, as was the average initial pore size (51-125 Å). The formation of hydroxycarbonate (HCA) and amorphous calcium phosphate (ACP) was observed at 14 days for samples stabilized at 650 or 750°C. Only ACP layers were observed on such samples prior to 14 day. Relative to the Ca levels at 14 day (60-485 μg/ml), Zn levels in solution were relatively low (0.06-1.18 μg/ml). EDX and ICP data suggested that released Zn was incorporated into the forming calcium phosphate reaction layer, thereby preventing concentrations of the essential trace element from reaching potentially toxic levels. © 2007 Wiley Periodicals, Inc.

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Journal of Biomedical Materials Research - Part A