Introduction

This chapter begins by reviewing the structure and origin of polysaccharides commonly used in hydrogels and then moves on to a brief discussion of the role of structural polysaccharides throughout tissues in the body. Common chemical modification techniques are discussed, followed by approaches used to crosslink polysaccharides into insoluble hydrogels. The authors will also describe recent research approaches for polysaccharide hydrogel materials as scaffolds for tissue engineering, vehicles for drug delivery, and tissue adhesives. The goal of this chapter is to provide the reader with an overview of the exciting potential of polysaccharide-based hydrogels in medicine.

Structure and origin of common polysaccharides

Polysaccharides are large linear or branched carbohydrate molecules composed of repeating monomer units. They can perform structurally, as in the extracellular matrix of animals and cell walls of plants [1], or provide energy storage capacity in the instances of glycogen and starch [2]. Every organism on the planet has the ability to produce polysaccharides. Solubilities of polysaccharides in water vary depending on the chemical structure [3]. Monomer units often contain chemical groups that can be functionalized chemically in order to modify their material properties. Important structural polysaccharides in the human body are known as glycosaminoglycans (GAGs), which are anionic, linear polysaccharides composed of repeating disaccharide units. The repeat unit is comprised of a hexosamine and either a hexose or hexuronic acid.