Photorelease of human stromal cells from gels for flow cytometry. hS5 stromal cells stably expressing BFP, GFP, and mCherry were encapsulated in PEG-tetraBCN hydrogels crosslinked with the appropriate photocleavable crosslinker (RuPink with hS5-mCherry+, RuOrange with hS5-GFP + , and oNB with hS5-BFP + ). All three hydrogels were cast in the same tissue culture dish, allowed to form for 30 minutes, then incubated in RPMI media for 24 hours. Hydrogels were transferred to PBS and exposed to 617 nm, 530 nm, or 405 nm light (10 mW cm - 2 , until hydrogel degradation was observed) and the resulting cell suspension was collected and analyzed by flow cytometry. Any hydrogels left intact after irradiation were imaged using confocal fluorescent microscopy.