Vancomycin-modified silica: Synthesis, controlled release and biological activity of the drug.

Vancomycin was immobilized on three different organically functionalized silicas. The materials obtained were used for a controlled release of the antibiotic. The influence of the type of chemical bond on the in vitro drug release was investigated. A weak ionic bonding caused burst release of the drug within one day. A covalent bonding resulted in a slowdown in the release process and uniformity of dosage release. For these two carriers, biological activity of the drug was retained because the minimal inhibitory concentration values against the strains tested were similar to that of a free form of the drug (about 2 μg/mL). A strong ionic bonding of vancomycin adversely affected both the drug release, as well as its biological activity. A strong base on the surface of the silica prevented disconnection of the antibiotic which then became ineffective.