Engineering triple synergistic coupling effects in g-C₃N₄-supported axially coordinated Ru single atoms/clusters to enhance multienzyme-mimicking activity for delaying osteoarthritis

Excessive chondrocyte-derived reactive oxygen/nitrogen species (RONS) disrupt redox homeostasis, leading to osteoarthritis (OA) progression. Nanozymes that mimic antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) offer a promising therapeutic strategy for OA by regulating the redox microenvironment. However, limited enzyme activity and biosafety hinder clinical translation. This study describes a ligand-mediated polymerization restriction approach for the design of ultrathin two-dimensional g-C₃N₄-supported nanozymes co-anchored with atomically dispersed Ru–N₅ sites and Ru clusters (RuSA+AC). The results show that RuSA+AC had a trinity synergistic effect of axial N-ligand Ru-N5 modulation → electronic coupling of Ru atoms and atomic cluster double sites → g-C₃N₄ carrier/active center interactions. The strategy not only optimized the d-band center modulation, enhanced the stability of Ru atoms, and improved radical adsorption/activation, but also localized electron redistribution and orbital overlap (Ru-d and radical-p), thus enhancing its multi-enzyme mimicry capabilities (SOD/CAT/GPx). In vitro and in vivo studies demonstrated RuSA+AC had the biosafety, RONS scavenging ability, as well as mitochondrial protection, inflammation inhibition, and reduced apoptosis, thereby delaying OA. Mechanistically, RuSA+AC activated the Nrf2/ARE pathway, which upregulates endogenous antioxidants (HO-1, NQO-1) and downregulates inflammatory factors. These findings could advance the design principles of nanozymes and suggest a potential paradigm for redox-targeted therapy against oxidative stress-related diseases.