Lu Peng, Mingxu You, Quan Yuan, Cuichen Wu, Da Han, Yan Chen, Zhihua Zhong, Jiangeng Xue, and Weihong Tan Journal of the American Chemical Society Article ASAP
This paper outlines the development of DNA-acrylamide hybrid hydrogels that convert light energy to volume changes. The hydrogels are synthesized by a two step method where two separate strands of acrylamide that have been copolymerized with complementary DNA strands are permanently cross-linked using methylenebisacrylamide. The DNA strands are modified with azobenzene duplexes that isomerize from trans to cis when irradiated with UV light. Under visible light conditions, the DNA strands are allowed to hybridize creating extra cross-links that cause the hydrogel to exist in a shrunken state. When irradiated with UV light, the cis-trans isomerization of azobenzene causes the DNA strands to denature allowing the hydrogel to expand. Using control experiments, the authors demonstrate that the volume changes are indeed tied to the photo-induced isomerization (though azobenzene was shown to slowly relax to its trans state in the dark due to thermal factors). They also demonstrate the reversibility of the volume changes over many cycles of visible and UV light irradiation. Studies on how the concentration of various elements effect swelling were also carried out with the results that more permanent cross-links created for less change overall while more DNA strands made for a more shrunken initial state.