Sustained Release of Nitric Oxide and Cascade Generation of Reactive Nitrogen/Oxygen Species via an Injectable Hydrogel for Tumor Synergistic Therapy

Reactive nitrogen species (RNS) generated via the reaction of nitric oxide (NO) with reactive oxygen species (ROS) are more lethal than ROS, and thus RNS-mediated therapy has great potential in cancer treatment, yet it is still largely unexploited. Herein, a novel, injectable and NO-releasing hydrogel (NO-Gel) composed of alpha-(nitrate ester) acetic acid-modified amphiphilic copolymers is developed. To further convert released NO to RNS, glutathione (GSH)-sensitive CuCys nanoparticles (NPs) and beta-lapachone (Lapa) are co-loaded into the NO-Gel. This hydrogel system possesses a temperature-induced sol-gel transition and can continuously liberate Lapa, CuCys NPs, and NO in vitro for up to 3 weeks. The sustained supply of Lapa can efficiently boost hydrogen peroxide (H2O2) concentration in cancer cells, and intracellular GSH can induce the rapid release of NO and the reduction of CuCys NPs. With elevating H2O2 levels and producing highly reactive Cu(I), the Cu(I)-catalyzed Fenton-like reaction is dramatically enhanced, resulting in the generation of abundant hydroxyl radicals (center dot OH), and the subsequent cascade reactions among center dot OH, H2O2, and NO cause more lethal RNS pool. After a single peritumoral injection of the hydrogel system, the cascade generation of ROS and RNS plus the substantial depletion of GSH can significantly suppress tumor growth.