Photocleavable side groups to spatially alter hydrogel properties and cellular interactions

Hydrogel systems with inducible variations in mechanical and chemical properties are of interest to many aspects of tissue engineering. Substrate-tethered hydrogel films, fabricated by copolymerization of hydroxyethylacrylate with the photolabile monomer 2-nitrobenzyl acrylate (2-NBA) and a crosslinker were shown to be responsive to UV light through cleavage of the 2-NBA moiety. The surface and bulk properties of the films were characterized by infrared spectroscopy and atomic force and confocal microscopy. At long irradiation times, a tripling of the swelling ratio and an order of magnitude decrease in gel modulus were observed, coupled with an increase in surface wettability. Following short exposures, the gels became resistant to protein and cell adhesion, a trend that was reversed with longer exposure times. Finally, high-fidelity patterns of gel swelling were fabricated through spatially selective irradiation by employing basic photomasks. These materials are useful for future studies for which spatial and temporal control of material properties and cellular interactions are desirable.