Chitosan cross-linked poly(acrylic acid) hydrogels: Drug release control and mechanism.

Chitosan has been used to cross-link poly(acrylic acid) to give three pH-sensitive hydrogels designed to control the release of the drugs amoxicillin and meloxicam. The extent of cross-linking and solution pH was found to dominate the swelling behavior of these hydrogels as shown by scanning electron microscopy and swelling time dependencies. The rates of release of amoxicillin and meloxicam from the loaded hydrogels increased with increase in pH consistent with the extent of hydrogen bonding between hydrogel components and between the hydrogel and the drugs being important determinants of release rate. Both the Korsemeyer-Peppas and Weibull models fitted release data consistent with drug release occurred through a combination of drug diffusion and hydrogel relaxation processes. These hydrogels appear to provide an ideal basis for controlled drug delivery systems.