Hydrogels in Regenerative Medicine

Publisher Summary This chapter provides an overview of the basic theory of hydrogels and their important uses and applications in regenerative medicine. Hydrogels could be considered amorphous, semicrystalline, hydrogen bonded, or complexation products. They could be classified according to their source, that is, whether they are naturally derived or synthetic. Synthetic systems have a variety of options and might be homopolymer or copolymer systems. Synthetic polymers could also be synthesized to form interpenetrating polymer networks in which the two polymer sheets are physically entangled. Naturally derived systems may be polysaccharide or polypeptide-based and derived from numerous sources. Three important parameters that need to be considered in defining hydrogels are the volume fraction in the swollen state, the crosslink density, and the porosity of the hydrogel and these parameters could be described mathematically. The method of hydrogel formation is particularly important for maintaining bioactivity of molecules and for minimizing any detrimental effects to cells associated with the gels. A monomer or noncrosslinked polymer is found in the solution (sol) phase. Upon application of some initiation conditions, the sol phase forms the hydrogel (gel) phase; that is, it undergoes the sol-gel transition. For hydrogels containing bioactive molecules or cells, the high temperatures and many monomers, solvents, and polymerization initiators could not be used due to inactivation of bioactives or cytotoxicity.