Enhanced multi-enzyme activity and bone-targeted phosphorus-doped carbon dots for precise antioxidant therapy of rheumatoid arthritis

Rheumatoid arthritis is a chronic autoimmune disorder characterized by the pathological accumulation of reactive oxygen species (ROS), which contributes to sustained inflammation and tissue damage. Current therapeutic modalities frequently exhibit low rates of clinical remission, and effectively mitigating the oxidative stress microenvironment associated with excessive ROS presents a significant challenge. Herein, we present a novel carbon dots (CDs) with multi-enzyme activity, featuring a porphyrin iron core and surface functional groups rich in phosphorus and oxygen, providing abundant catalytic sites for enhanced scavenging of hydrogen peroxide, hydroxyl radicals, and superoxide anions. Furthermore, the phosphate groups on the surface of CDs exhibited a specific affinity for hydroxyapatite, thereby facilitating targeted delivery to the bone. The localized accumulation of CDs with multi-enzyme activity at inflammatory lesions can effectively reduce oxidative stress levels, subsequently inhibiting bone destruction in collagen-induced arthritis rat models and significantly alleviating disease symptoms. This study integrates multiple catalytic sites and targeting moieties into a single nanostructure, representing a promising strategy for the precise treatment of oxidative stress-related bone pathologies.