Preparation and Characterization of Cross-Linked Chitosan Microcapsules for Controlled Delivery of Oxytetracycline

Formulations of encapsulated oxytetracycline in chitosan spherical beads have been developed in this work through the ionotropic gelation method in sodium tripolyphosphate or tripolyphosphate and characterized as drug delivery system to the gastrointestinal tract by Fourier transform infrared spectroscopy spectroscopy, thermal analysis and in vitro drug release in simulated gastric fluids. The Fourier transform infrared spectroscopy and differential scanning calorimetry measurements showed that tripolyphosphate and tripolyphosphate are cross linked ionically to chitosan and there was no significant drug interaction between the entrapped drug and the carrying polymer. With the respect to chitosan cross linking features, sodium hexametaphosphate seems to give better swelling, higher diffusion and faster release kinetics, while addition of glutaraldehyde as a second cross linking agent lowers the drug discharge. Release extent and kinetics were found to be pH dependent and approximated very well by the multistep models equations of Makoid-Banakar, Peppas-Sahlin and Korsmeyer-Peppas.