Carbon dot nanozymes: Mechanisms of ROS modulation and biomedical applications

Reactive oxygen species (ROS) play a dual role in maintaining redox homeostasis and mediating pathological signal transduction in the body. Their imbalance is closely associated with various diseases, including inflammatory diseases, tumor progression, and bacterial infections. In recent years, carbon dot nanozymes have emerged as promising candidates for managing oxidative stress-related diseases, benefiting from their favorable biocompatibility, tunable structural characteristics, and multimodal ROS-regulating capabilities. This review systematically summarizes the structural regulation strategies of carbon dot nanozymes and their mechanisms for modulating ROS behavior. Specifically, we highlight how varying structural features, driven by precursor selection, elemental doping, surface modification, and environmental or physical stimuli, dictate their distinct roles in both antioxidant and pro-oxidant processes. Furthermore, this review comprehensively examines their biomedical applications, spanning anti-inflammatory and antioxidant therapy to pro-oxidant tumor treatments and antibacterial/antibiofilm applications. By clarifying their advantages and limitations in complex pathological microenvironments, we also critically analyze the current challenges in mechanistic understanding, in vivo behavior, and clinical translation. Finally, this review discusses future development directions to inspire the rational design and biomedical application of novel ROS-regulating nanomaterials.