Preparation and characterization of freeze-dried chitosan-poly(ethylene oxide) hydrogels for site-specific antibiotic delivery in the stomach

Purpose. The purpose of this study was to develop novel drug delivery systems with pH-sensitive swelling and drug release properties for localized antibiotic delivery in the stomach. Methods. The drug delivery systems were synthesized by crosslinking chitosan and poly(ethylene oxide) (PEG) in a blend to form semiinterpenetrating polymer network (semi-IPN). Scanning electron microscopy was used to compare the surface and bulk morphology of the freeze-dried and air-dried chitosan-PEO semi-IPN. The hydrogels were allowed to swell and release the antibiotics-amoxicillin and metronidazole-in enzyme-free simulated gastric fluid (SGE pH 1.2) and simulated intestinal fluid (SIE pH 7.2) at 37 degrees C. Results. Freeze-dried chitosan-PEO semi-IPN with a porous matrix had swollen extensively as compared to the air-dried hydrogel. The swelling ratio of freeze-dried and air-dried chitosan-PEO semi-IPN after 1 h in SGF was 16.1 and 2.30, respectively. More than 65% of the entrapped amoxicillin and 59% of metronidazole were released from the freeze-dried chitosan-PEO semi-IPN after 2 h in SGF Conclusions. The results of this study suggest that freeze-dried chitosan-PEO semi-IPN could be useful for localized delivery of antibiotics in the acidic environment of the gastric fluid.