Hybrid Shear-thinning Hydrogel Integrating Hyaluronic Acid with ROS-Responsive Nanoparticles.

Nanoparticle (NP) supra-assembly offers unique opportunities to tune macroscopic hydrogels' mechanical strength, material degradation, and drug delivery properties. Here, synthetic, reactive oxygen species (ROS)-responsive NPs are physically crosslinked with hyaluronic acid (HA) through guest-host chemistry to create shear-thinning NP/HA hydrogels. A library of triblock copolymers composed of poly(propylene sulfide)--poly(N,N-dimethylacrylamide)--poly(N,N-dimethylacrylamide--N-(1-adamantyl)acrylamide) are synthesized with varied triblock architectures and adamantane grafting densities and then self-assembled into NPs displaying adamantane on their corona. Self-assembled NPs are mixed with β-cyclodextrin grafted HA to yield eighteen NP/HA hydrogel formulations. The NP/HA hydrogel platform demonstrates superior mechanical strength to HA-only hydrogels, susceptibility to oxidative/enzymatic degradation, and inherent cell-protective, antioxidant function. The performance of NP/HA hydrogels is shown to be affected by triblock architecture, guest/host grafting densities, and HA composition. In particular, the length of the hydrophilic second block and adamantane grafting density of self-assembled NPs significantly impacts hydrogel mechanical properties and shear-thinning behavior, while ROS-reactivity of poly(propylene sulfide) protects cells from cytotoxic ROS and reduces oxidative degradation of HA compared to HA-only hydrogels. This work provides insight into polymer structure-function considerations for designing hybrid NP/HA hydrogels and identifies antioxidant, shear-thinning hydrogels as promising injectable delivery platforms for small molecule drugs and therapeutic cells.