Heteronuclear Single‐Atom Nanozymes Overcome Radiotherapy Resistance via Synergistic Multi‐Enzyme Activities

Single‐atom nanozymes have revolutionized catalytic tumor therapy by maximizing atomic efficiency and enabling enzyme‐mimetic reactive oxygen species (ROS) generation. Yet, their single active‐site architecture imposes fundamental limitations on catalytic selectivity and intermediate adsorption–desorption kinetics. Here, a manganese/ruthenium dual‐metal single‐atom nanozyme (Mn/Ru BMSA) is reported that overcomes these constraints through synergistic metal interactions, exhibiting unprecedented multienzyme activities, including catalase, peroxidase, and superoxide dismutase. By leveraging tumor‐overexpressed hydrogen peroxide, Mn/Ru BMSA simultaneously alleviates hypoxia and produces cytotoxic hydroxyl radicals, creating a self‐sustaining catalytic cycle that amplifies ROS for radiotherapy synergy. Density functional theory calculations reveal that Mn coordination modulates the d‐band center of Ru, optimizing electronic structure to enhance substrate activation. In radioresistant breast cancer models, Mn/Ru BMSA exhibits a synergistic triple‐modal antitumor action: 1) sustained oxygen generation alleviates tumor hypoxia, 2) X‐ray‐enhanced ROS production amplifies oxidative stress, and 3) hypoxia‐inducible factor 1α pathway inhibition suppresses cancer stem cell (CSC) stemness (as validated by transcriptomics). Patient‐derived organoid assays demonstrated complete radioresistance reversal while maintaining exceptional biosafety. This work establishes Mn/Ru BMSA as a potential radiosensitizer that overcomes the limitations of conventional high‐Z materials by targeting the hypoxia‐CSC axis, providing a strategy for developing multi‐functional nanozymes against treatment‐resistant cancers.