Hydrogel

A class of polymeric materials known as hydrogel products have a hydrophilic structure that allows them to store enormous amounts of water in their three-dimensional networks. More than any other form of synthetic biomaterial, they most nearly resemble genuine living tissue because of their high water content, porosity, and soft consistency. Hydrogels may also be prepared into a wide range of physical forms, such as coatings, films, microparticles, and slabs. Hydrogels are so often utilized in clinical practice and medicine for a variety of purposes, such as cellular immobilization, tissue engineering and regenerative medicine, diagnostics, separation of biomolecules or cells, and barrier materials to control biological adhesions. This biomaterial has the capacity to expand and store huge volumes of biological fluids. They are mushy when swollen.

  Eye, which is the most vital organ of the body suffer from various eye problems like glaucoma, endopthalmitis, dry eye syndrome, trachoma, keratitis, conjunctivitis etc. Most ocular diseases are treated by topical drug application in the form of solutions, suspensions and ointment. These conventional dosage forms suffer from the problems of poor ocular bioavailability because of dilution and rapid drainage. Prolonged drug delivery can be achieved  by various new dosage forms like in-situ gel, collagen shield, minidisc, ocular film, ocusert, nanosuspension, nanoparticulate system, liposomes, niosomes, dendrimers, ocular iontophoresis etc. The most successful of these is the in-situ forming ophthalmic drug delivery systems prepared from polymers that exhibit reversible liquid-gel phase transition .The aim of this article is to present a concise review of in-situ gelling system to overcome all above problems. This review also summarizes various temperature, pH, and ion induced in-situ forming polymeric systems used to achieve prolonged contact time of drugs with the cornea and increase their bioavailability.

  Hydrogel are three-dimensional, cross-linked networks of water-soluble polymers. Hydrogels can be made from virtually any water-soluble polymer. Injectable hydrogels are hydrogels which can given by parenteral route by use of injection and syringe. Such hydrogels are of particular interest because drugs, proteins, and cells can be easily incorporated into polymer solutions prior to administration.  Injectable hydrogel administrated in solution form by use of standard needles and syringes, it solidifies upon contact with aqueous body fluids to form gel. Drug release occurs over time as polymer biodegrades. This review will provide summary of recent progress in Injectable hydrogel, polymer used and method of preparation of Injectable hydrogel, evaluation of hydrogel and recent application of Injectable hydrogel. Key words: Hydrogel, Injectable hydrogel, Thermal and pH sensitive Injectable hydrogel, novel drug delivery system of Injectable hydrogel.

  Hydrogel nanoparticles have gained considerable attention in recent years as one of the most promising nanoparticulate drug delivery systems owing to their unique potentials via combining the characteristics of a hydrogel system with a nanoparticle. Therefore, it seems that the pharmacy world will benefit from the hydrophilicity, flexibility, versatility, high water absorptivity, and biocompatibility of these particles and all the advantages of the NPs, mainly long life span in circulation and the possibility of being actively or passively targeted to the desired bio-phase. Several polymeric hydrogel nanoparticulate systems have been prepared and characterized in recent years, based on both natural and synthetic polymers, each with its own advantages and drawbacks. Several cross linking methods have been used in the way to form the hydrogel matrix structures. The remainder of this text presents various types of nanogels prepared and characterized, using a classification based on the type of polymeric materials used in preparation of the NPs.   Key words: Hydrogel, Nanoparticles, Hydrogel nanoparticles, Nanogels, Hydrogel.