Fig. 1. (a) Photoresponsive hydrogel components spiropyran methacrylate (i, SPMA), carboxybetaine acrylamide (ii, CBAA), cRGD-functionalized CBAA (iii) and crosslinker carboxybetaine dimethacrylate (CBDMA). (b) Reversible photochromism of spiropyran between its hydrophobic spiropyran (SP) and hydrophilic merocyanine (MC) forms. (c) Representative photograph of photodynamic hydrogels receiving NIR, NG-1, NG-2 and green light exposure. (d) UV-Vis absorption spectra of photodynamic hydrogels receiving NIR, NG-1, NG-2 and green light exposure. (e and f) Photodynamic process of the MC ⇌ SP conversion in hydrogels receiving different light exposures starting from either a green hydrogel (e) or NIR hydrogel (f).