Properties and applications of hydrogels in medicine: A review

Hydrogel is a three dimensional water insoluble polymeric network that can absorb body fluids in a biological environment. Its polymer network structure can be formed by chemical cross-linking such as photo-polymerization, enzyme-catalyzed reactions, and physical cross-linking induced by temperature, pH, and ionic interaction. Physical hydrogel is formed by weak secondary interaction. Covalent bonds are normally formed among polymer chains in a chemically crosslinked hydrogel. To synthesize hydrogels, natural and synthetic polymers were applied. Swelling, mechanical and biological properties of the hydrogels are the most important parameters that can be affected on its structure and morphology. The large volume of water that they can absorb and an ability to mimic the extracellular matrix environment are the main reasons for use the hydrogels for many biomedical applications such as tissue engineering, contact lenses, wound healing, and the controlled delivery of therapeutic agents. This review covers the various mechanisms of hydrogel formation, types of hydrogels, their properties and applications in the medicine.