Chitosan/pectin polyelectrolyte complexes: characterization and application in colon-specific delivery systems

In this study the influence of different preparative conditions of polyelectrolyte complexes composed of chitosan and pectin on the release behaviour of vancomycin was investigated. Vancomycin is a peptide drug indicated for the treatment of serious, lifethreatening infections by Gram-positive bacteria which are unresponsive to other less toxic antibiotics. In particular, in the treatment of pseudomembranous colitis, vancomycin must be given orally to reach the site of infection. The most challenging in the development of pharmaceutical systems for an efficient local therapy is overcome problems like acid catalyzed degradation in the stomach and proteolytic breakdown in the gastro-intestinal tract. In the development of colon-specific delivery systems of peptide drugs, pH-sensitive hydrogels have attracted increasing attention. Swelling of hydrogels in the stomach should be minimal, instead water absorption and drug release should increase as the hydrogels pass down the intestinal tract due to an increase in pH. Several synthetic or natural polymers with acidic or basic groups have been employed to prepare pH-sensitive hydrogels. Chitosan is a natural derivative of chitin with interesting biological properties, including biocompatibility, biodegradability and mucoadhesivity. Chitosan is a polycation and has been used extensively to prepare ionically crosslinked hydrogels with anionic polymers [1]. Chitosan/pectin polyelectrolyte complexes were prepared in various pH regions and at different molar ratios by mixing solutions of pectin and chitosan with the same ionic strength. The precipitates were collected by spray-drying and tablets were obtained with the different complexes and vancomycin. In vitro water uptake, mucoadhesion and release tests were performed in order to investigate the polyelectrolyte complex ability in the delivery of vancomycin in the gastro-intestinal tract. [1] Berger, J., Reist, M., Mayer, J.M., Felt, O., Peppas, N.A., Gurny, R. (2004) Structure and interactions in chitosan hydrogels formed by complexation or aggregation for biomedical applications. Eur. J. Pharm. Biopharm., 57, 35-52.