Tricolor Visible Wavelength-selective Photodegradable Hydrogel Biomaterials

Photodynamic hydrogel biomaterials have demonstrated great potential for user-triggered therapeutic release, patterned organoid development, and 4D control over advanced cell fates in vitro. Current photosensitive materials are constrained by their reliance on high-energy ultraviolet (UV) light (<400 nm) that offers poor tissue penetrance and limits access to the broader visible spectrum. Here, we report a family of three photolabile material crosslinkers that respond rapidly and with unique tricolor wavelength-selectivity to low-energy visible light (400 – 617 nm). When mixed with multifunctional poly(ethylene glycol) macromolecular precursors, novel ruthenium polypyridyl- and ortho-nitrobenzyl (oNB)-based crosslinkers yield cytocompatible biomaterials that can undergo spatiotemporally patterned, uniform bulk softening, and multiplexed degradation several centimeters deep through complex tissue. Encapulated living cells within these photoresponsive gels show high viability (>85%) and can be successfully recovered from the hydrogels following photodegradation. Moving forward, we anticipate that these advanced material platforms will enable new studies in 3D mechanobiology, controlled drug delivery, and next-generation tissue engineering applications.