Influence of synthesis and processing conditions on the release behavior and stability of sol-gel derived silica xerogels embedded with bioactive compounds.

The influence of processing parameters and synthetic strategies in the properties of sol-gel derived silica matrices intended for the release of bioactive compounds was investigated. The time-evolution of the matrix properties during its aging at room temperature in the dry and wet forms was investigated by measuring some of its physical and drug retaining properties. The results indicate that long term gel aging in the wet form is fundamental for the obtainment of dry matrices that are stable upon storage, a fundamental requirement for any practical application. In the case of hybrid matrices obtained by replacing part of the tetraethoxysilane precursor with mono-methyl trimethoxysilane, the order of addition of the reaction component is also important in determining the properties of the final dry gel, probably by influencing the polymer structural properties. This parameter acts synergistically with the matrix composition in determining the release properties of xerogels embedded with bioactive compounds.