Figure 1.

Mechanochemical interactions in multi-fiber hydrogel networks through the reaction of complementary chemical groups. (a) Schematic of the electrospinning of two fiber populations from hyaluronic acid modified with norbornenes (NorHA), as well as either hydrazides (NorHA-Hyd, red) or aldehydes (NorHA-Ald, green). Norbornenes are used for intra-fiber and inter-fiber crosslinking through a photoinitiated thiol-ene reaction to stabilize the fiber, while the hydrazides and aldehyde groups permit additional inter-fiber reactions when fibers are brought into contact. Inset shows hydrazide and aldehyde groups exposed on fiber surface after electrospinning, stabilization, and hydration. (b) Schematic (top) and fluorescent images (bottom) of mechanical strain-induced interactions between hydrazide (colored red or containing red fluorophore) and aldehyde (colored green or containing green fluorophore) containing NorHA fibers (i) before, (ii) during, and (iii) after applying strain for 40 minutes. After removal of strain, permanent deformations of “adhesive” fibers are observed through fluorescent microscopy (yellow indicating coinciding red and green fluorophores). (c) Schematic (top) and fluorescent images (bottom) indicating a lack of mechanical strain-induced interactions in “non-adhesive” fiber control under the same loading conditions. The multi-fiber hydrogel control is fabricated from mixed fibers of unmodified NorHA and NorHA-Ald fiber populations, where no chemical reaction is expected when the fibers contact each other. Scale bar is 100 µm.