A greenish gel that fluoresces in response to temperature and pH changes has been created by coupling a polymer scaffold with an activated protein.The hybrid material potentially could be used for the construction of various sensors, actuators and drug-delivery systems. The substance has the added advantage of being biodegradable.Researchers Aaron P. Esser-Kahn and Matthew B. Francis of the University of California, Berkeley, report that the hydrogel was constructed by cross-linking chains of polymer with proteins that display a structure-dependent function.A fluorescent green gel created by researchers could be used for a variety of sensing applications.Unlike other fabrication methods with hybrid material that rely on specific coupling and that cannot be used with some protein side chains, the technique devised by the investigators is much more flexible. It is — in principle — usable with any protein. The coupling occurs at both ends of the protein chain, which are the same for all proteins. The ends areactivated concurrently and then attached to special points on the polymer, creating a 3-D network and, ultimately, the hydrogel. Details of the research appear in the May 5, 2008, issue of Angewandte Chemie International Edition.The hydrogel was heat-tested, and its fluorescence and swelling were measured. The investigators found that the substance began to shrink and that its fluorescence declined at around 70 °C. This trend continued until fluorescence stopped and a large size reduction occurred at 75 °C.