Hydrogels: a smart drug delivery device

Among various investigations hydrogels have attracted much attention Hydrogels are three-dimensional, hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluid and swell. When swelled, they are soft & rubbery and resemble the living tissue. The various preparation techniques adopted are physical cross-linking, chemical cross-linking, grafting polymerization, and radiation cross-linking for the preparation of hydrogels. These biomaterials have gained attention owing to their peculiar characteristics like swelling in aqueous medium, pH and temperature sensitivity or sensitivity towards other stimuli. Hydrogels being biocompatible materials have been recognized to function as drug protectors, especially for peptides and proteins, from in-vivo environment. Also, these swollen polymers are helpful as targetable carriers for bioactive drugs with tissue specificity. Generally hydrogels are characterized for their morphology, swelling property, chemical structure and rheology. Morphological studies performed by using scanning electron microscopy (SEM) give us information about porous structure of hydrogels. Swelling determines the release mechanisms of the drug from the swollen polymeric mass while rheology give information about hydrogels.The hydrogels have been used extensively in various biomedical applications, viz. drug delivery, cell carriers and/or entrapment, wound management and tissue engineering. This article has been devoted to study the common methods of preparation, characterization, and application of hydrogels.