ENVIRONMENTAL RESPONSIVE HYDROGELS: A NOVEL APPROACH IN DRUG DELIVERY SYSTEM

Hydrogels are three dimensional crosslinked hydrophilic polymeric networks which has the capability to imbibe water or biological fluids. Environmentally responsive hydrogels have the ability to respond to change in their external environment. They can exhibit dramatic changes in their swelling behaviour, network structure, permeability and mechanical strength in response to change in pH or ionic strength of the surrounding fluid or temperature. Other hydrogels have the ability to respond to applied electric or magnetic field or to change in concentration of glucose. Environmental responsive hydrogels for drug delivery application also requires biocompatibility. The chemical structure of the polymer may also affect the swelling ratio of hydrogels. Hydrogels containing hydrophilic groups swell to a higher degree compared to those containing hydrophobic groups. Swelling of environmentally responsive hydrogels can be affected by changes in the temperature of the swelling media, ionic strength and pH