Au/N-Doped Carbon Dot Nanozymes as Light-Controlled Anti- and Pro-Oxidants

Disturbances in the redox state of a biological system can cause diverse effects and clinical functions. The key and difficulty lies in controlling the balance between reduction and oxidation. Nanomaterials with oxidoreductase-like activity offer an appealing way to adjust anti- and pro-oxidation in response to biological conditions. To this end, we design and prepare visible light-responsive hybrid nanozymes by combining Au and N-doped carbon dots (Au/NC). It is found that Au/NC can efficiently scavenge reactive oxygen species (ROS) and free radicals and exhibit SOD-like activity, showing intrinsic antioxidant activity. Upon irradiation with visible light, we observe that Au/NC can generate ROS (e.g., hydroxyl radicals, superoxide, and singlet oxygen) and exhibit enhanced oxidase-like activity to accelerate the oxidation of chromogenic substrates, showing pro-oxidant capability. The light-activated oxidative activity is ascribed to the synergistic effects of photoexcitation of N-doped carbon dots and the surface plasmon resonance of Au nanoparticles. In addition, we demonstrate the application of the anti- and pro-oxidant capability of Au/NC in inhibition or acceleration of oxidation of Monascus pigments and Fe 2+, which is switched by the incident light. These results will be of significant interest in modulating the biological redox conditions through responsive and precise nanozymes.