Mn−Ce Symbiosis: Nanozymes with Multiple Active Sites Facilitate Scavenging of Reactive Oxygen Species (ROS) Based on Electron Transfer and Confinement Anchoring

Regulating appropriate valence states of metal active centers, such as Ce³⁺/Ce⁴⁺ and Mn³⁺/Mn²⁺, as well as surface vacancy defects, is crucial for enhancing the catalytic activity of cerium-based and manganese-based nanozymes. Drawing inspiration from the efficient substance exchange in rhizobia-colonized root cells of legumes, we developed a symbiosis nanozyme system with rhizobia-like CeO_x nanoclusters robustly anchored onto root-like Mn₃O₄ nanosupports (CeO_x/Mn₃O₄). The process of “substance exchange” between Ce and Mn atoms—reminiscent of electron transfer—not only fine-tunes the metal active sites to achieve optimal Ce³⁺/Ce⁴⁺ and Mn³⁺/Mn²⁺ ratios but also enhances the vacancy ratio through interface defect engineering. Additionally, the confinement anchoring of CeO_x on Mn₃O₄ ensures efficient electron transfer in catalytic reactions. The final CeO_x/Mn₃O₄ nanozyme demonstrates potent catalase-like (CAT-like) and superoxide dismutase-like (SOD-like) activities, excelling in both chemical settings and cellular environments with high reactive oxygen species (ROS) levels. This research not only unveils a novel material adept at effectively eliminating ROS but also presents an innovative approach for amplifying the efficacy of nanozymes.