Overview

Polymeric hydrogels are of special importance in polymeric biomaterials because of their favorable biocompatibility. Hydrogels are cross-linked macromolecular networks formed by hydrophilic polymers swollen in water or biological fluids. The cross-links can be formed by either covalent bonds or physical cohesion forces that exist between the polymer segments. Polymeric hydrogels are primarily classified into chemical and physical hydrogels (based on the bonding type of the cross-links), though they can also be classified in many other ways. Chemical hydrogels can be prepared by copolymerization of a monomer with cross-linker, or by cross-linking of water-soluble polymers. Physical hydrogels can be made of natural biopolymers, thermo-sensitive synthetic polymers, amphiphilic triblock copolymers or many other copolymers. Further, polyelectrolyte complexes and polymer-cyclodextrin inclusion complexes can likewise form hydrogels. All chemical and physical hydrogels described in this chapter are of biomedical significance. Their biomedical applications in drug delivery and tissue engineering are hence discussed.

7.1 Introduction

Of many polymeric biomaterials, hydrogels are of special interest because of their favorable biocompatibility and a host of unique advantages that accompany them. For example, hydrogels play an important role in controlled drug delivery: they are able to deliver delicate bioactive agents such as proteins and peptides. In addition, hydrogels have also been reported to promote tissue repair and regeneration. In this chapter, a general overview of polymeric hydrogels in...