Silica sol-gel for the controlled release of antibiotics. II. The effect of synthesis parameters on the in vitro release kinetics of vanomycin.

Room temperature-processed silica sol-gel (xerogel) was investigated as a novel controlled release carrier of vancomycin for the treatment of osteomyelitis. Vancomycin-loaded xerogels were fabricated with varying water/alkoxysilane molar ratios and vancomycin concentrations. The goal of this study was to determine the effect of varying the aforementioned synthesis parameters on the daily in vitro release kinetics of vancomycin from the xerogel disks. A controlled, load-dependent, long-term release of vancomycin was observed for all of the molar ratios that were used in the study (4, 6, and 10). Variations in the water/alkoxysilane molar ratio affected the release process extensively. A cumulative release of about 90% of the original amount of vancomycin was found for molar ratios 6 and 10 by 21 and 14 days, respectively. Only about 30% was released from xerogels with a molar ratio of 4 after 21 days of immersion. A first-order release stage was followed by a steady release stage for xerogels with molar ratios of 6 and 10, whereas zero-order release was observed for xerogels with a molar ratio of 4. The findings of this study indicate that the release kinetics of vancomycin from xerogel can be tailored by varying the xerogel synthesis parameters.