Mn-CDs with oxidase activity produces ROS to inhibit cell activity

Carbon dots (CDs) played increasingly important roles in biotechnology due to their potential as alternatives of natural enzymes. However, the fabrication of highly active and durable CDs remains challenging and catalytic reaction mechanisms over CDs needs to be better clarified for future advances. Herein, we synthesized manganese-doped carbon dots (Mn-CDs, ∼5 nm) with excellent oxidase properties which exhibits stable catalytic capacity in various salt solutions at different temperatures. Moreover, by thoroughly investigating catalytic ability of Mn-CDs, we found that doped Mn atoms effectively modulated the spin density and charge distribution of CDs, thus reducing the band gap by forming intermediate energy levels. Besides, it is found that the content of pyrrolic N positively correlated to catalytic capacity of Mn-CDs. As a demonstration, the prepared Mn-CDs could work as pseudo-oxidase in real cell environment. They can easily enter into cells, induce the production of ·O2− under ultraviolet light irradiation, and eventually inhibit the activity of HeLa cells and 4T1 cells. We believe that the as-prepared Mn-CDs would find wide applications as metal-doped artificial nanozymes, and lay a foundation for the application and development of Mn-CDs.