Having demonstrated that hydrogel responses could be controlled in a wavelength-specific manner using visible light, we next sought to investigate the cytocompatibility of gel formation via SPAAC reaction and subsequent photodegradation. 10T ½ mouse fibroblasts were encapsulated (5 x 10 6 cells mL -1 ) in Rubiq, Rubpy, and oNB hydrogels (Fig. ). Live/dead staining with calcein/ethidium homodimer and fluorescent confocal imaging was performed 24 hours after encapsulation. High viability was observed in all cases (Fig. ), consistant with SPAAC's reported biocompatibility for gel formation and that of the crosslinkers 50 . To assess the cytocompatibility of photodegradation, cell-laden gels were photodegraded with red, green, or blue visible light 1 day post encapsulation. In a subset of the gels, released cells were left suspended in hydrogel photoproducts for an additional 24 hours, after which the cells that adhered were stained for viability (Fig. ). Fibroblasts showed normal morphology 24 hours after plating, suggesting the photodegradation process did not alter them significantly. To confirm viability following release, cells were collected following hydrogel degradation and assessed directly for viability via flow cytometry (Fig. ). Though viability was generally high, results demonstrated that fibroblasts released from Rubiq-crossedlinked gels were less viable than the other hydrogel formulations, suggesting that the Rubiq photoproduct may be partially cytotoxic.