Nanozyme with Robust Catalase Activity by Multiple Mechanisms and Its Application for Hypoxic Tumor Treatment

Utilizing catalase-mimicking nanozymes to produce O₂ is an effective method to overcome tumor hypoxia. However, it is challenging to fabricate nanozymes with ultrahigh catalytic activity. Palladium nanosheet (Pd NS), a photothermal agent for photothermal therapy (PTT), has superior catalase-mimicking activity. Here, titanium dioxide (TiO₂ ) is used to modify Pd NS (denoted Pd@TiO₂ ) by a simple one-step method to improve its catalytic activity about 8 times. The enhancement mechanism's fundamental insights are discussed through experiments and density functional theory calculations. Next, zinc phthalocyanine is loaded on Pd@TiO₂ to form a nanomotor (denoted PTZCs) with the synergistic activities of photodynamic therapy and PTT. PTZCs inherit the catalase activity of Pd@TiO₂ to facilitate the decomposition of endogenous H₂ O₂ to O₂ , which can relieve tumor hypoxia and propel PTZC migration to expand the reach of PTZCs, further enhancing its synergistic treatment outcome both in vitro and in vivo. It is proposed that this work can provide a simple and effective strategy for catalytic activity enhancement and bring a critical new perspective to studying and guiding the nanozyme design.