Soft and jelly like structure, physical properties, higher permeability and release of entrapped drug in controlled and lower interfacial tension, manner have made hydrogels to focus on exploration in different biomedical fields in particular hydrogels have been used extensively in the development of drug delivery system. These unique physico-chemical properties of hydrogels have emerged their particular interest in their use in drug delivery system. These are three-dimensional, hydrophilic, polymeric networks capable of absorbing and retaining large amounts of water or biological fluids. Their affinity to absorb and retain a large amount of water is attributed to the presence of hydrophilic groups such as –OH, CONH–, –CONH2–, and –SO3H in polymers forming hydrogel structures. Due to the contribution of these hydrophilic groups in the network make the polymer hydrated to different degrees (sometimes, more than 90% wt.), their high water content, porosity and soft texture and consistency, they closely resemble to natural living tissues. Hydrogels may be chemically stable or they may degrade and eventually disintegrate and dissolve. The purpose of this present review is to describe some advances in hydrogels, in its preparation methods, their application in biomedical and pharmaceutical fields.
