Phosphorous containing chitosan (PCTS) was synthesized by a graft copolymerization technique in order to be used as controlled drug delivery devices. To test this potential, PCTS beads were prepared by using tripolyphosphate, at pH 4.0 and characterized by scanning electron microscopy. The in vitro drug release behavior in various pH solutions was studied using indomethacin (IM) as a model drug at two different concentrations (0.3 and 0.6% w/w). The release percent of IM from PCTS beads was found to be increased with the increasing of pH in the buffer solution. The release rate of IM at pH 7.4 was higher than that at pH 1.4, due to the ionization of phosphorous groups and the high solubility of IM in the alkaline medium. These results indicated that PCTS beads have the potential to be used as controlled drug delivery systems through oral administration by avoiding the drug release in the highly acidic gastric fluid region of the stomach
Dr. Jayakumar Rangasamy, Reis, R. L., and Mano, J. F., “Phosphorous Containing Chitosan Beads for Controlled Oral Drug Delivery”, Journal of Bioactive and Compatible Polymers, vol. 21, pp. 327-340, 2006.