Rationally engineered Pd–Os nanosheets eliminating reactive oxygen and nitrogen species for in situ nanocatalytic therapy of ear inflammation

Nanozymes with robust antioxidant properties hold great promise for the treatment of inflammatory diseases associated with reactive oxygen and nitrogen species (RONS). Herein, we designed and synthesized two-dimensional Pd-Os nanozymes via a one-pot synthesis strategy, where Os was incorporated onto Pd nanosheets (NSs). The prepared Pd-Os NSs with outstanding antioxidant efficacy and enzyme-like activities could scavenge hydrogen peroxide and superoxide anion radicals through catalase (CAT) and superoxide dismutase (SOD) activities and efficiently eliminate hydroxyl radicals (˙OH) and reactive nitrogen radicals (DPPH). Furthermore, the antioxidant activity of Pd-Os NSs demonstrated significant protective effects against oxidative stress in cellular models induced by hydrogen peroxide, as evidenced by cell viability assays and confocal microscopy imaging. Finally, Pd-Os NSs were used to treat the mouse ear acute inflammation induced by phorbol 12-myristate 13-acetate, and various data and indicators such as mouse ear section, mouse blood routine and blood biochemistry verified that Pd-Os NSs still had a remarkable ability to mitigate RONS in vivo, thus achieving a good therapeutic effect against ear inflammation.