HYDROGELS: A REVIEW ON CLASSIFICATION, PREPARATION METHODS, PROPERTIES AND ITS APPLICATIONS

Hydrogels are composed of three dimensional cross linked polymer network. The hydrogels shows excellent biocompatibility, when swelled and resemble the living tissue. High water content of hydrogels and physiochemical similarities to the native extracellular matrix, both compositionally and mechanically promotes biocompatibility. The evaluation of biocompatible properties consider more attention before the hydrogels are applied. Due to the higher water absorption capacity, long service life, and wide varieties of raw chemical resources natural hydrogels were gradually replaced by synthetic types. For hydrogel production, different technologies adopted with process design implications, block diagrams, and optimized conditions of the preparation process. Based on the different classification, hydrogels could be homo-polymeric, co-polymeric, semi-interpeneterating and interpeneterating polymer networks. These are categorized as natural, synthetic and semisynthetic and based upon polymer used they can be temperature triggered, pH triggered and ion activated and in this case these are known as smart gels. Hydrogels can be used as biosensors as well as drug delivery systems that are responsive to specific molecules, such as glucose or antigens,. Hydrogels are used in different biomedical fields such as cellular immobilization, specific site drug delivery, tissue reconstruction, tissue engineering, as biosensors, diagnostics and separation of molecules due to their unique properties and are also used in contact lenses. In this review article an attempt has been made to describe the available methods of hydrogel synthesis, classification of hydrogels, their properties, methods of preparation and its applications. Keywords: Hydrogels, Biocompatibility, Polymer, Immobilization, Chemical cross-linking