Microscopic and spectroscopic investigation of bioactive glasses for antibiotic controlled release

Bioactive glass with the composition 0.55SiO2·0.41CaO·0.04P2O5 was prepared following the sol–gel route as controlled delivery systems for tetracycline (TC). The maturation and drying of the gel under different conditions led to different behavior regarding the loading and release of TC from these matrices. The pore size modifications upon TC loading evidenced by BET method show different ability of the glass matrices with respect to TC incorporation, also supported by experimental EPR and fluorescence spectroscopy. EPR spectra of both TC solution and immobilized TC on the porous structure of glass specimens demonstrated changes in tetracycline structure during loading and upon adsorption. The TC release profile monitored by differential pulse voltammetry shows a maximum concentration after 2 h and a continuously slow release during the next 24 h. The obtained results demonstrate that the pores size modification related to different maturation and drying procedures seems to be a determinative factor in tetracycline release process.