'Smart gel' supplies drug to painful joint when it moves

U.S. scientists say they developed a squishy gel that when compressed -- like at a painful knee joint -- releases anti-inflammatory medicine. Xinqiao Jia, Chandran R. Sabanayagam and colleagues at the University of Delaware said in the past few decades, researchers have been developing a variety of "smart" hydrogels that can release medications over several days rather than in a single burst. Most of these gels release medicine all the time or in response to changes in temperature, light or other factors. Very few respond to physical pressure, which is what causes pain in the 27 million U.S. osteoarthritis patients. For those with osteoarthritis -- the "wear-and-tear" type of arthritis -- the cartilage between the bones becomes damaged and wears away, making everyday movements of the knees, hands, backs and hips severely painful. Jia and Sabanayagam created a special type of hydrogel that responds to compression -- such as the pressure between joints that occurs in everyday movement -- and loaded it with the anti-inflammatory drug dexamethasone. When the hydrogel was compressed in the laboratory, it boosted the release of the drug. The researchers said they are currently testing their smart pain medications in laboratory animals. The findings are published in the journal Biomacromolecules.