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

Abstract

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 <i>in vitro</i> and <i>in vivo</i>. 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.