Perspectives of biodegradable natural polysaccharides for site-specific drug delivery to the colon

The ability to deliver drugs to the human colon in a specific manner has become feasible over the years. Targeting pharmaceutical drugs to the colon makes it possible to achieve local or systemic drug delivery to this site. To deliver the compounds in a non-degraded form to the lower part of the gastrointestinal tract, they must first of all pass through the stomach, the upper part of the intestine and must use the characteristics of the colon to specifically release the drugs in this part of the digestive tract. Among the different approaches available to achieve targeted drug release to the colon, the use of especially biodegradable polymers holds great promise. This family of natural polymers has great appeal to drug delivery as it is comprised of polymers with a large number of derivatizable groups, a wide range of molecular weights, varying chemical compositions, and, for the most part, low toxicity and biodegradability yet high stability. The most favorable property of these materials is their approval as pharmaceutical excipients. Polysaccharidases are bacterial enzymes that are available in sufficient quantity to be exploited in colon targeting. Bacterial sources of polysaccharidases as well as a detailed treatise of the enzymatic flora of the colonic region is reviewed, followed by a wide range of the polysaccharides which can be used solely for the purpose of colon-specific drug delivery. Present article also discusses few of the mechanisms by which members of the intestinal microbiota degrade complex polysaccharides. A final overview of the various approaches to target drugs to the colon utilizing natural polysaccharides, the limits and the future developments in this field with these natural polymers is discussed which leads to the conclusion that polysaccharides show high potential in achieving colon-specific drug delivery.