Synthesis and characterization of pH-sensitive thiol-containing chitosan beads for controlled drug delivery applications

摘要

The aim of this study was to develop chitosan-based materialsin drug delivery systems possessing covalent attachment of thiolmoieties. Thiol-containing chitosan (TCS), found to be soluble inwater, was synthesized by graft copolymerization technique. TheTCS beads were prepared by using tripolyphoshate, at pH 4.0.The morphology of TCS beads was examined by scanning electronmicroscopy. The in vitro drug release behavior was studied inphosphate buffer solution at various pH, using indomethacin as amodel drug at two different concentrations (0.3 and 0.6% w/w).The release amounts of indomethacin from TCS beads were higherincreasing pHs in the dissolution medium. The release rate of indomethacinat pH 7.4 was higher than the release rate at pH 1.4 dueto ionization of thiol groups and high solubility of indomethacin inan alkaline medium. These results indicated that the TCS beadsmay become a delivery system for the controlled release of differentdrugs wherever pH sensitive mechanics might be useful. Thisis especially applicable in cases when it is important to minimizedrug release in acidic sites, such as in the stomach.