AHYDROGEL-DRUG SYSTEM that relies on the consecutive action of two trigger mechanisms to release a drug has the potential to target specific sites within the body according to the scientists in the Netherlands who developed the system. triggers are a stimulus that converts the gel into a solution and an enzyme that cleaves the hydrogelator- drug link. Raising the temperature or lowering the pH causes more low-molecular-weight gelator molecules to come out of the gel fibers and go into solution, says Kjeld J. C van Bommel, a researcher at Biomade Technology Foundation, Groningen, who carried out the work with Jan van Esch, assistant professor of chemistry at the University of Groningen, and coworkers ( Org. Biomol. Chem. 2005,3,2917). Only when they are in solution can the molecules be cleaved by an enzyme and the drug be released, van Bommel continues. The combination of a low-molecular-weight gelator gel sensitive to both its environment and ...