pH sensitive methacrylated chitosan hydrogels with tunable physical and chemical properties

The pH of cutaneous wounds is dynamic and correlates with the stage of the wound healing process. The inflammation stage is acidic, granulation shifts to a progressively alkali pH, and the remodeling phase returns skin to its pre-injury pH. By taking the advantage of this pH difference, stage-specific wound treatments can be developed to respond to these environmental cues using pH sensitive hydrogels. To obtain tunable physical and chemical properties, chitosan was first methacrylated and then crosslinked through three polymerization methods step growth by a thiol-ene photoclick reaction, chain growth by UV polymerization, and mixed mode in which both step growth and chain growth mechanisms were used. pH sensitive methacrylated chitosan (MAC) hydrogels were synthesized and confirmed through 1H NMR. The resulting hydrogels exhibited adjustable mechanical properties, swelling ratios, and pH sensitivities without affecting degradation behavior or in vitro cell responses. Cytocompatibility studies were performed using NIH/3T3 fibroblasts. Cell proliferation or adhesion was suppressed when seeded on the hydrogel surfaces compared to tissue culture plastic (TCP), yet no measureable cell death was observed. The responsivity of these gels to changing pH environments may prove useful as stage-responsive wound dressings.