Enzymatically-responsive Qk-releasing hydrogels were formed in non-degradable reactors and implanted subcutaneously in mice. One week after implantation, vascularization into the reactor was assessed via A) hemoglobin content and B–C) by multiphoton fluorescent imaging. B) Representative images of collagen (SHG, blue) and vasculature (FITC-dextran, red) formed within reactors. C) Quantification of average vessel diameter. n.s. p>0.05, * p<0.05, $ p<0.001. n=14–16 for A, 6–8 for C; error bars represent SEM. Scale bar = 100 µm.