Ultrasmall copper nanoclusters with multi-enzyme activities

Reactive oxygen species (ROS) as a key messenger of signal transduction mediate physiological activities, however, oxidative stress produced by excessive ROS can cause the destruction of cell homeostasis, which will result in a series of diseases. Therefore, effective control of ROS level is critical to the homeostasis of the cell. Here, we reported that glutathione (GSH)-stabilized copper nanoclusters (CuNCs) with about 9 Cu atoms can functionally mimic three major antioxidant enzymes, namely catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD). The rate of H2O2 decomposition was calculated to be similar to 0.23 mg L-1 s(-1) when the concentration of CuNCs was 100 mu g mL(-1). The SOD-like activity by catalyzing the disproportionation of superoxide (02) to H2O2 and O-2 reached 25.6 U mg(-1) when the effective inhibition rate was similar to 55.4%. Intracellular ROS scavenging studies further identified that CuNCs can obviously protect cells from oxidative stress and the cell viability recovered to above 90%. Hence, we expect that ultrasmall CuNCs will provide good therapeutic potential in the future treatment of ROS-related diseases.