Highlighting the Influence between Physical and Chemical Cross-Linking in Dynamic Hydrogels for Two-Photon Micropatterning.

Photolabile hydrogels have gained tremendous interest for a wide range of applications in materials and life sciences. Usually, photodegradability is introduced via chromophores and labile bonds, making such materials intrinsically light sensitive. In recent years, disulfide bonds have emerged as an innovative alternative, as they can be selectively cleaved in the presence of (photo)generated radicals. However, such materials suffer from limited network stability and high swelling as a result of thiol-disulfide metathesis reactions. Herein, we present two strategies to counteract such phenomena by network stabilization either via physical or chemical incorporation of (un)modified gelatin macromers to norbornene-modified poly(vinyl alcohol) networks. Photolabile behavior was introduced by a simple disulfide-containing dithiol cross-linker. Tunable material properties were investigated by means of in situ photorheology, in vitro swelling, and degradation experiments. Finally, we demonstrate an innovative method for localized disulfide cleavage via two-photon micropatterning.