Figure 3. GuHCl reversibly modulates the elasticity of crosslinked I91₈ biomaterials.

(A) Results of force-extension cycles (0.667 mm/s) conducted on a 7 mm I91₈ gel in PBS (black, solid), after 42 minutes in GuHCl (gray), and 23 minutes after return to PBS (black, dashes). At 40% strain (2.8 mm stretch) during the extension, the Young’s modulus of the gel is reduced ~35 fold upon incubation in GuHCl. Subsequent incubation in PBS increases the Young’s modulus to 1.14 times the original value. We also observe a large increase in hysteresis. (B) Young’s modulus at 20% strain at different incubation times in GuHCl (gray) and after removal of GuHCl and incubation in PBS (black). Young’s moduli are given relative to the Young’s modulus before incubation in GuHCl. In this experiment, the hydrogel was attached to the force sensor and the voice coil using cyanoacrylate-based glue.