Polysaccharides for Colon–Targeted Drug Delivery: Improved Drug–Release Specificity and Therapeutic Benefits

Abstract

Ulcerative colitis (UC) is a chronic, immunologically-mediated disorder which affects the gastrointestinal tract. This disease is characterized by inflammation of the colonic or rectal mucosa, leading to rectal bleeding, diarrhea, and abdominal pain. UC, along with Crohn’s disease, is referred to as inflammatory bowel disease. The specific cause of this disease is unknown, but research has suggested that it is most likely initiated by a combination of host susceptibility and environmental triggers. These factors lead to an overly-aggressive T-cell response to bacteria in the gastrointestinal tract. An abnormal ratio between beneficial and detrimental microbes in the gut may also contribute to the development of this disease, as well as defects in the function of the intestinal mucosal barrier. No medical cure has been developed for UC; treatment focuses on inducing and maintaining remission (Sartor, 2006). Anti-inflammatory drugs, particularly those that contain 5-aminosalicylic acid (5-ASA), are often used to treat UC. The effectiveness of these aminosalicylate drugs is related to their mucosal concentration. Because free 5-ASA is rapidly absorbed in the small intestine, this drug must be encapsulated or conjugated to be effectively delivered to the colon. Methods for colonic delivery of 5-ASA include chemically attaching it to a carrier molecule or encapsulating it with pH or time-release polymers, but these methods exhibit various limitations (Caprilli et al., 2009). The use of polysaccharides as conjugate or encapsulation materials has been explored as a means of targeting the delivery of 5-ASA to the colon. The purpose of this chapter is to discuss approaches to using polysaccharides as colon-targeted drug delivery systems, and to discuss how using polysaccharides in these drug formulations may provide therapeutic benefits beyond drug delivery.