Fig. 13. Selective cell release via photodegradation using differences in reactivity of o-nitrobenzyl groups. (A), (B) o-Nitrobenzyl linkers with different degradation kinetics were used to vary the degradation rate of adjacent hydrogels. (C) RFP-expressing hMSCs and GFP-expressing hMSCs were encapsulated within hydrogels made with (A) or (B), where the two hydrogels were in direct contact with each other (RFP = red fluorescent protein, GFP = green fluorescent protein). (D) The interface between hydrogels containing RFP- and GFP-expressing hMSCs was observed using optical microscopy. (E) Gels were exposed to light (10 mW cm–2 at 365 nm, 30 minute total duration), resulting in a biased release of one cell population over another (R GFP/R RFP ∼ 2.4) which was consistence with the degradation rate constants of (A) and (B) (k app A/k app B ∼ 2.5). Image reprinted from Griffin et al. 280 with permission from American Chemical Society. Copyright (2012).
