Targeted delivery of 5-ASA to colon using chitosan hydrogel microspheres

The present study is aimed at developing hydrogel microspheres of chitosan grafted with vinyl polymers for the controlled release of 5-ASA to the colon in rodents. The graft copolymer of chitosan with acrylamide was synthesized and used to prepare microspheres by water-in-oil (w/o) emulsification method (CHI-g-AAm). The microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic swelling and in vitro drug release. The prepared microspheres were spherical with smooth surfaces. The in vitro 5-ASA release from chitosan hydrogel microspheres exhibited significantly higher drug release in simulated colonic fluid containing caecal and colonic content than that in the simulated stomach and small intestinal fluid. Drug release in simulated fluids such as simulated intestinal fluid (SIF-pH 7.0), was found to be 84.4 ± 1.8% and 91.1 ± 1.3% in the presence of 5 and 10% rat caecal content (RCC), respectively, at the end of 8 h. The drug loaded microspheres were also studied for the healing of 2,4,6-trinitrobenzene sulfonic acid sodium salt (TNBS)-induced colitis in rats. The colonic injury and inflammation were assessed by measuring the myeloperoxidase (MPO) activity, colon wet weight/body weight (C/B) ratio and the damage score, respectively. Grafted chitosan microspheres bearing 5-ASA exhibited better therapeutic effects as evaluated by the MPO activities, C/B ratio and the damage score in comparison to 5ASA plain drug solution in oral administration.