Catalyzing Generation and Stabilization of Oxygen Vacancies on CeO_2−x Nanorods by Pt Nanoclusters as Nanozymes for Catalytic Therapy

Although CeO₂ nanomaterials have been widely explored as nanozymes for catalytic therapy, they still suffer from relatively low activities. Herein, the catalyzing generation and stabilization of oxygen vacancies on CeO₂ nanorods by Pt nanoclusters via H₂ gas reduction under mild temperature (350 °C) to obtain Pt/CeO_2−x, which can serve as a highly efficient nanozyme for catalytic cancer therapy, is reported. The deposited Pt on CeO₂ by the atomic layer deposition technique not only can serve as the catalyst to generate oxygen vacancies under mild temperature reduction through the hydrogen spillover effect, but also can stabilize the generated oxygen vacancies. Meanwhile, the oxygen vacancies also provide anchoring sites for Pt forming strong metal-support interactions and thus preventing their agglomerations. Importantly, the Pt/CeO_2−x reduced at 350 °C (Pt/CeO_2−x-350R) exhibits excellent enzyme-mimicking catalytic activity for generation of reactive oxygen species (e.g., ·OH) as compared to other control samples, including CeO₂, Pt/CeO₂, and Pt/CeO_2−x reduced at other temperatures, thus achieving excellent performance for tumor-specific catalytic therapy to efficiently eliminate cancer cells in vitro and ablate tumors in vivo. The excellent enzyme-mimicking catalytic activity of Pt/CeO_2−x-350R originates from the good catalytic activities of oxygen vacancy-rich CeO_2−x and Pt nanoclusters.