Synthesis and in vitro characterization of freeze-dried doxorubicin-loaded silica/PEG composite

Freeze-dried doxorubicin-loaded silica/poly(ethylene glycol) composites have been prepared by a two-step acid/base catalyzed sol–gel process from tetraethylorthosilicate in the presence of poly(ethylene glycol) (PEG). PEG was used as a pore-forming agent, followed by liberation process of PEG during the in vitro doxorubicin release study. Simulated body fluid (SBF, Kokubo solution) at 37 °C with ion concentrations nearly equal to those of human blood plasma (pH 7.4) was used for in vitro evaluation. The characteristics of these composites before and after drug release, including the infrared absorption spectra, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) in combination with IR and nitrogen gas adsorption/desorption, were measured and analyzed. The relationship between the liberation process of PEG and rate of drug release is discussed mainly in terms of molecular and structural features of the silica composites before and after drug release study. It was shown that an increase in the proportion of PEG in the silica network was associated with an increase in degree of hydration (higher hydrophilicity) and average pore size, and with a decrease in bulk density, specific surface area, and also degree of polymerization of silica. The rate of drug release increases with an increase in PEG content. These results are in line with the increase in specific surface area and mesopore size of these composites and also correspond to a more polymerized and thermally stable silica network obtained after drug release study.