Modulation of zinc release from bioactive sol-gel derived SiO(2)-CaO-ZnO glasses and ceramics.

Zinc is an essential trace element which may be effective in promoting hard tissue healing. Glasses in the SiO(2)-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 degrees C), to examine such effects on the bioactive response and zinc release in simulated body fluid (SBF). XRD revealed the development of CaSiO(3) and Ca(2)ZnSi(2)O(7) crystalline phases during stabilization at 850 degrees C only. N(2) adsorption analysis determined that the specific surface area (BET) varied between 14 and 179 m(2)/g and was dependent on composition and stabilization temperature, as was the average initial pore size (51-125 A). The formation of hydroxycarbonate (HCA) and amorphous calcium phosphate (ACP) was observed at 14 days for samples stabilized at 650 or 750 degrees C. Only ACP layers were observed on such samples prior to 14 day. Relative to the Ca levels at 14 day (60-485 microg/ml), Zn levels in solution were relatively low (0.06-1.18 microg/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.