PdZn/CoSA‐NC Nanozymes with Highly Efficient SOD/CAT Activities for Treatment of Osteoarthritis via Regulating Immune Microenvironment

Abstract Inflammatory infiltration of synovial M1 macrophages, high levels of ROS, and NO exacerbate osteoarthritis (OA) progression. The PdZn/CoSA‐NC nanozymes, which are highly ordered PdZn intermetallic nanoparticles loaded with Co single atom N‐doped carbon‐rich in multi‐level pores, in an attempt to serve as SOD and CAT mimicking nanozymes for OA therapy is designed. The PdZn/CoSA‐NC nanozymes' high electron transfer and dual active site sufficient exposure enhances free radical adsorption and lower reaction energies, accelerating SOD‐like, CAT‐like, and GPx‐like catalyzed reactions, outperforming CoSA‐NC and PdZn/NC alone. Furthermore, PdZn/CoSA‐NC nanozymes exhibit favorable biocompatibility, reduce synovial macrophage oxidative stress in OA, alleviate hypoxia, restore mitochondrial function, regulate energy metabolism, increase antioxidant factors, and reduce inflammatory factors, thus effectively mitigating the progression of OA. Mechanistically, PdZn/CoSA‐NC nanozymes downregulate M1‐type phenotypic markers like IL‐1β by regulating purine metabolism. The PdZn/CoSA‐NC nanozymes offer a novel approach to treating oxidative stress‐related inflammatory diseases.