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

The Fe3O4 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 Fe3O4 nanozyme partly due to its low affinity to the substrate H2O2. Herein, we report a new strategy for improving the peroxidase-like activity and affinity of the Fe3O4 nanozyme to H2O2 to generate reactive oxygen species (ROS) for kidney tumor catalytic therapy. We showed that cobalt-doped Fe3O4 (Co@Fe3O4) nanozymes possessed stronger peroxidase activity and a 100-fold higher affinity to H2O2 than the Fe3O4 nanozymes. The lysosome localization properties of Co@Fe3O4 enable Co@Fe3O4 to catalyze the decomposition of H2O2 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@Fe3O4 nanozyme is a powerful nanozyme for the generation of ROS bursts upon the addition of H2O2 at ultralow doses, presenting a potential novel avenue for tumor nanozyme catalytic therapy.