Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogels are crosslinked three-dimensional hydrophilic polymer networks capable of retaining a significant amount of water within their structures, and swell without dissolving in water.1 A hydrogel is formed when an organic polymer (natural or synthetic) is crosslinked via covalent, ionic, or hydrogen bonds to create a three-dimensional structure.2 Recently, much work has been carried out on the synthesis and characterization of pHand temperature-sensitive hydrogels by copolymerization and crosslinking. Interpenetrating polymer networks (IPNs) have also been synthesized and used in a wide range of applications including artificial implants, dialysis membranes, wound dressings, etc., suggesting their enormous potential as drug delivery systems. IPNs are defined as a combination of two or more polymers, each in a network form, at least one of which is synthesized and/or crosslinked in the immediate presence of the other. Several reviews have been published describing both applications and fundamental theory of IPNs.3 In the recent past, there has been considerable interest in developing controlled drug delivery systems using natural polymers due to their non-toxicity, biodegradability and biocompatibility. Chitosan (CS) is a linear polysaccharide composed of randomly distributed -(1–4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit) (Fig. 1).4 It is produced commercially by deacetylation of chitin, the structural element in the exoskeleton of crustaceans (crabs, shrimp, etc.).5 CS is widely used in biomedical and pharmaceutical applications because of its unique chemical and biologic properties. It is a cationic polysaccharide (pKa ~6.3) soluble at acidic pH, and bioadhesive, which increases retention at the site of application and readily binds to negatively charged surfaces such as mucosal membranes. Mucoadhesive formulations have been developed for ocular, nasal, buccal, gastrointestinal, and vaginal drug adSorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum