Hydrogel based drug delivery system: A review

Hydrogels are the three-dimensional hydrophilic network which is crosslinked physically or chemically. Hydrogels are also called as hydrophilic gels because they absorb considerate amount of water. The characteristic properties of hydrogels are swelling, mechanical properties, biodegradable, elasticity, biocompatible, easy to modify, flexibility, etc. They are classified based on source, polymeric composition, biodegradability, configuration, cross linking, physical appearance, chemical charges, and drug release. Hydrogels can be synthesized from natural, synthetic, semisynthetic polymers via physical, chemical crosslinking, through grafting, coacervation and polymerization. The hydrogels are useful in daily life and their major applications are drug delivery to oral cavity, GI tract, rectal, ocular, protein, subcutaneous, transdermal, controlled drug delivery, preparation of contact lenses, wound healing, tissue engineering, biosensing, bacterial culture preparation, and various other fields like agriculture, electronics, cosmetics, gene delivery, perfume delivery, regenerative medicine, plastic surgery, sealant adhesive, watering beads for plant and water purification.