Copper single-atom carbon dots hydrogel resets oxidative and immune homeostasis for rheumatoid arthritis therapy.

Rheumatoid arthritis pathogenesis is perpetuated by a self-sustaining oxidative stress-immunodysregulation circuit. To address the limitations of conventional antioxidants, including unclear catalytic structures and single catalytic activity, we engineered copper single-atom carbon dots via topological transformation of sodium copper chlorophyllin. Encapsulated within a pH-responsive injectable hydrogel, this system achieves targeted delivery to inflamed joints, where it simultaneously scavenges superoxide anions and hydrogen peroxide, breaking the reactive oxygen species-inflammation cycle. Treatment reprograms macrophage polarization, suppresses pathogenic B-cell infiltration, and mitigates cartilage erosion. By integrating nature-inspired atomic catalysis with intelligent biomaterial engineering, this approach establishes a paradigm for resetting oxidative-immune microenvironments in autoimmune diseases.