Cell-laden hydrogels are used as three-dimensional scaffolds to examine and direct cell fate in culture. Light responsive, and in particular, photodegradable hydrogels possess many advantages stemming from their ability to be modified in space and time in a user-defined manner. Until now, photodegradation has been achieved based on incorporation of a photoactive species directly into the polymer backbone and cleavage of that molecule. This strategy suffers from slow kinetics because a single photon can cleave, at most, a single crosslink. We have developed a hydrogel platform that can be degraded through a radical addition-fragmentation chain transfer mechanism. Upon exposure to light in the presence of a photoinitiator, rapid exchange between network allyl sulfides and free monofunctional thiols results in network degradation. The kinetics of this reaction far surpass those achieved with hydrogels that rely on alpha photocleavage of a molecule in the polymer backbone. This reaction also proceeds in a cytocompatible manner, and cells remain viable through encapsulation in the AFCT hydrogel and subsequent release. Additionally, we have adapted this scheme to leverage the rapid network reorganization that occurs during exposure of allyl sulfide-crosslinked hydrogels to a radical source, to create hydrogels with spatiotemporally tunable viscoelastic properties.

Photodegradable, photoadaptable hydrogels crosslinked by allyl sulfides for cell culture applications

254th National Meeting (2017)

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