Improved polymer functionality by cross-linking with glutaraldehyde to achieve controlled drug release

Abstract

There are many approaches to combine drug and polymers. One of them involves the use of drug-polymer conjugates in which the drug is covalently bounded to a polymer through a hydrolyzable linkage. However, the most widely used approach involves polymers as matrixes in which the drug and polymer are mixed physically and the release is achieved by diffusion from the surrounding polymeric matrix or by disintegration of the polymeric matrix. Nevertheless, most biopolymers per se do not possess adequate physicochemical and mechanical properties to produce a film or hydrogel which can be used as a matrix for the controlled release of drugs. For this reason, many cross-linking agents have been used to improve these polymer properties. The most reactive and typical cross-linking agent employed is glutaraldehyde. This chapter discusses the modification of drug release properties of polymers suchs as poly(vinyl) alcohol, chitosan, gelatin, alginates, carrageenan and naturally occurring gums by chemical modification via glutaraldehyde cross-linking. Most cross-linked products are more amorphous due to the reduction of the hydroxyl network responsible for cross-linking, crystallinity and water interaction.