Photoreductive Degradation of Fe(III)-Catechol Crosslinked Hydrogels under Visible Light.

Hydrogels that degrade in response to external stimuli have attracted interest as dynamic materials for controlled release and biomedical applications. Light is particularly appealing as a non-invasive trigger, yet most photodegradable hydrogels rely on ultraviolet irradiation, which can induce cellular damage depending on wavelength and dose. Here we present a hydrogel system that undergoes reductive disassembly of Fe(III)-catechol crosslinks under visible light. Incorporation of Fe(III)-citrate into a catechol-conjugated polymer generated a hydrogel network that could be destabilized upon irradiation. A variety of analyses revealed a clear transition from a gel-like to a liquid-like state, confirming that photoreduction of Fe(III) to Fe(II) drives the network degradation. This structural disruption enabled functional release of encapsulated cargo molecules, which was markedly enhanced relative to the controls. Moreover, the release rate could be systematically tuned by light intensity, consistent with photon-flux-dependent photoreduction. We envision that the visible-light-degradable hydrogels herein have potential applications in spatiotemporally controlled material disassembly across diverse fields.