Tetracycline and propolis incorporation and release by bioactive glassy compounds

This study compares the release of tetracycline and propolis incorporated into four silica-based bioactive glassy systems. The bioactive glasses, with composition (SiO2)x(P2O5)y(CaO)z, were prepared using a sol-gel process at room temperature. Tetraethoxysilane (TEOS), triethylphosphate, and calcium chloride were used as Si, P, and Ca precursors, respectively. The quantities of tetracycline and propolis incorporated were 2% in weight. For delivery assays, the samples were individually immersed in deionized water and buffered with tris-hydroxymethyl amino methane, pH 7.4, and kept in water bath (37 °C) for thirty days. Aliquots were withdrawn and analyzed by ultraviolet spectrophotometry in the tetracycline (270 nm) and propolis (420 nm) wavelengths. For the glass-tetracycline compounds, it was observed that four days after release had started all samples had released about 90% of the total tetracycline concentration. In contrast, 90% of the propolis was released in about 30 days' time. Sample characterization was made using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopic (FTIR), and thermogravimetry (TG).