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.