Light-Controllable PEG Hydrogel Cross-Linked by Reversibly Photodissociable Dimeric Green Fluorescent Protein pdDronpa for Drug Delivery.

Hydrogel has been widely studied as a carrier model system for drug delivery. Efficient encapsulation of drug molecules and their controlled release are important factors in the design of hydrogels to control drug release at a desired time and location. In this study, we propose a photoresponsive hydrogel with tunable mechanical properties for drug delivery. The hydrogel was synthesized by cross-linking maleimide-functionalized 4-armed polyethylene glycol (4-armed PEG-Mal) with reversibly photodissociable green fluorescent protein pdDronpa. Transitions in the physical state and/or mechanical strength of the hydrogel occurred rapidly when the cross-linking agent pdDronpa was switched off and on between the monomer and dimer states using 500 and 400 nm illumination, respectively. Optically controlled release of fluorescently labeled insulin was investigated, demonstrating the ability of this hydrogel as a potent drug delivery system.