A cobalt-doped iron oxide nanozyme as a highly active peroxidase for renal tumor catalytic therapy

The Fe(3)O(4) nanozyme, the first reported nanozyme with intrinsic peroxidase-like activity, has been successfully employed for various diagnostic applications. However, only a few studies have been reported on the therapeutic applications of the Fe(3)O(4) nanozyme partly due to its low affinity to the substrate H(2)O(2). Herein, we report a new strategy for improving the peroxidase-like activity and affinity of the Fe(3)O(4) nanozyme to H(2)O(2) to generate reactive oxygen species (ROS) for kidney tumor catalytic therapy. We showed that cobalt-doped Fe(3)O(4) (Co@Fe(3)O(4)) nanozymes possessed stronger peroxidase activity and a 100-fold higher affinity to H(2)O(2) than the Fe(3)O(4) nanozymes. The lysosome localization properties of Co@Fe(3)O(4) enable Co@Fe(3)O(4) to catalyze the decomposition of H(2)O(2) at ultralow doses for the generation of ROS bursts to effectively kill human renal tumor cells both in vitro and in vivo. Moreover, our study provides the first evidence that the Co@Fe(3)O(4) nanozyme is a powerful nanozyme for the generation of ROS bursts upon the addition of H(2)O(2) at ultralow doses, presenting a potential novel avenue for tumor nanozyme catalytic therapy.