Redox-Responsive Hydrogels with Decoupled Initial Stiffness and Degradation

Disulfide-cross-linked hydrogels have been widely used for biological applications because of their degradability in response to redox stimuli. However, degradability often depends on polymer concentration, which also influences the hydrogel mechanical properties such as the initial stiffness. Here, we describe a one-pot cross-linking approach utilizing both a thiol-ene reaction through a Michael pathway with divinyl sulfone (DVS) to form non-reducible thioether bonds and thiol oxidation promoted by ferric ethylenediaminetetraacetic acid (Fe-EDTA) to form reducible disulfide bonds. The ratio between these two bonds was modulated by varying the DVS concentration used, and the initial shear or elastic modulus and degradation rate of the hydrogels were decoupled. These gels had tunable release rates of encapsulated dextran when exposed to 10 μM glutathione. Fibroblast encapsulation results suggested good cytocompatibility of the cross-linking reactions. This work shows the potential of combining DVS and Fe-EDTA to create thiol-cross-linked hydrogels as redox-responsive drug delivery vehicles and tissue engineering scaffolds with variable degradability.