Cytocompatible click-based hydrogels with dynamically tunable properties through orthogonal photoconjugation and photocleavage reactions

The authors present a hydrogel network with two orthogonal light controlled functions. Thiol containing molecules can be covalently attached by the radical mediated thiol-ene reaction with visible light. The gel matrix can also be degraded by photocleaving at a nitrobenzyl moiety using UV light. These reactions are bioorthogonal and spatiotemporally controlled, allowing the material's properties to be regulated in real time. They demonstrated the utility of this matrix by encapsulating human mesenchymal stem cells. The cells were allowed to grow through regions of the hydrogel that had been modified by the thiol-ene reaction to contain integrin binding peptide ligands. The photocleaving reaction was then used to liberate cells at specific areas of the gel. Also, the authors encapsulated a cell-laden fibrin clot. Cell migration from the clot was controlled by both of the the photochemical reactions.