Chemical Ligations in the Design of Hydrogel Materials

This chapter reviews the methods employed to form hydrogels, the classes of polymers utilized in these materials, as well as some of the common chemistries exploited to cross-link the matrix into a stable hydrogel network. It focuses on ligation strategies which allow for in situ formation of hydrogels in biologic environments, as well as the decoration of preformed hydrogel networks. Selecting the proper ligation chemistry to build hydrogel networks plays a critical role in determining network morphology and, consequently, helps govern the physical properties of the bulk gel. Preparing gels via chemical ligation allows for temporal and spatial control over material formation. Classic chemical transformations have served as the inspiration for developing novel chemical ligation strategies. In general, the rapid expansion of new chemistries and innovative orthogonal techniques capable of selective ligations in complex biologic environments will open an array of opportunities for the future of material design.