Ir/CeO₂ Single‐Atom Nanoislands as an Atomic‐Nano System for Highly Efficient Self‐Cascade Glucose Oxidase and Peroxidase Mimics

Abstract The stability and activity of self‐cascade enzymes based on glucose oxidase (GOx) and peroxidase (POD) are usually low, which has significant limitations in tumor catalytic therapy. Building nanoislands‐supported single‐atom nanozymes with strong atomic‐nano interaction is an effective strategy for enhancing the self‐cascade enzyme‐like activity. Herein, noble metal iridium (Ir) single‐atoms are successfully deposited on CeO₂ quantum dots (QDs) nanoislands to construct Ir/CeO₂ single‐atom nanoislands (SANIs). The CeO₂ QDs nanoislands with abundant oxygen vacancies facilitate efficient electron transfer of Ir single‐atoms at the metal‐nanoislands interface. A liposomal nano platform encapsulated with Ir/CeO₂ SANIs (Ir/CeO₂@Lipo) is further developed for in vivo catalytic therapy. The Ir/CeO₂@Lipo exhibits excellent self‐cascade GOx‐ and POD‐like activity due to its unique atomic‐nano structures and the confined effect of the nanoislands. Compared with CeO₂@Lipo and other reported nanozymes, Ir/CeO₂@Lipo catalyzes glucose to generate more ROS with higher efficiency, demonstrating superior GOx‐POD self‐cascade enzyme‐like activity. In vivo, experiments demonstrate that Ir/CeO₂@Lipo possesses excellent tumor‐targeting capability as well as nearly complete tumor ablation through ROS‐mediated apoptotic pathways. Thus, this work provides a new paradigm for designing self‐cascade enzymes for tumor treatment strategies.