The Studies On The Synthesis And Properties Of Biodegradable Hydrogels For Colon-Specific Drug Delivery

For their biodegradability in bodies, biodegradable polymers used as biomedical materials have an extensive application and are developed rapidly. Biomedical polymers promote the development of both traditional pharmaceutics and modern controlled or targeted pharmaceutics. In this paper, the colon-specific drug delivery system, the synthesis and the biodegradation of the novel hydrogels, which are used for colon-drug delivery, have been reviewed.In colon, there is an abundant of the colonic bacteria, which produce a variety of enzymes and the typical enzymes include azoreductase, glycosidases, and glucuroridase. For lacking of proteinase, colon-delivery is the best approach for protein, peptide molecules and drugs. As to these characters, novel hydrogels for molecule drugs, which can be degraded by the enzymes in colon, were designed. The drug was released through the degradation of hydrogels. Therefore, the targeted-release of protein and peptide drugs can be realized.Konjac glucomannan(KGM) is a random copolymer of B-(1-4)linked D-mannose and D-glucose. Since it can be degraded by the B-glycosidase existed in colon but not in the upper gastrointestinal (GI) tract, the materials based on KGM can ensure the targeted-release of drugs. Its chemical stability, biodegradability and easily modified ability suggest their applications in targeted drug delivery systems.In this paper, the novel biodegradable hydrogels based on KGM for colon-specific delivery had been synthesized. For the azoreductase in colon tract, an biodegradable and pH-sensitive hydrogel crosslinked by azo segments was synthesized to increase its targeted and degradable abilities. The swelling, degradation and the drug release of the pH-sensitive hydrogel crosslinked by polyethylene glycol with different chain length were studied. The temperature-sensitive hydrogel, KGM grafted Poly(iV-isopropylacrylamide) (PNEPA), was also synthesized. We studied the effects of the reactive factors to the swelling behavior and degradation of these three kinds of hydrogels, and found the best reactive conditions. The results showed that theproduced copolymers had the pH-responsibility or the temperature-responsibility. The degradation of these hydrogels were evaluated by the reaction of buffer solution, steapsase, a-amylase and B-glycosidase. They just can be degraded by B -glycosidase like KGM. During the synthesis of the hydrogels, the modern drug bovine serum albumin (BSA) wad loaded. The research of drug release in different conditions showed that the progresses of drug release were controlled by the degradation of hydrogels. So the colon-specific drug release can be controlled by regulating the hydrogels' swelling behavior and degradation. The produced hydrogels were potential to be novel materials for colon-specific drug delivery.