Fig. 18. Modulation of substrate stiffness in a 2D dynamic microenvironment. (A) Incorporation of a photodegradable nitrobenzyl moiety in a hydrogel network, prepared using polyacrylamide acryl hydrate (PAAH) and a 4-bromomethyl-3-nitrobenzoic acid (BNBA) crosslinker, enabled gel degradation and softening using cytocompatible doses of UV light (365 nm). (B) Softening of the posterior substratum (rear) did not significantly alter cell spreading (left column). However, softening of the anterior substratum (front) led to reverse polarity (central column) or trapping in the softened region (right column; scale bar, 20 μm). Reprinted from Frey et al. 360 with permission from The Royal Society of Chemistry publishing group. Copyright (2009).
