An O2 Self‐Supplementing and Reactive‐Oxygen‐Species‐Circulating Amplified Nanoplatform via H2O/H2O2 Splitting for Tumor Imaging and Photodynamic Therapy

Abstract Conventional photodynamic therapy (PDT) has limited applications in clinical cancer therapy due to the insufficient O 2 supply, inefficient reactive oxygen species (ROS) generation, and low penetration depth of light. In this work, a multifunctional nanoplatform, upconversion nanoparticles (UCNPs)@TiO 2 @MnO 2 core/shell/sheet nanocomposites (UTMs), is designed and constructed to overcome these drawbacks by generating O 2 in situ, amplifying the content of singlet oxygen ( 1 O 2 ) and hydroxyl radical (•OH) via water‐splitting, and utilizing 980 nm near‐infrared (NIR) light to increase penetration depth. Once UTMs are accumulated at tumor site, intracellular H 2 O 2 is catalyzed by MnO 2 nanosheets to generate O 2 for improving oxygen‐dependent PDT. Simultaneously, with the decomposition of MnO 2 nanosheets and 980 nm NIR irradiation, UCNPs can efficiently convert NIR to ultraviolet light to activate TiO 2 and generate toxic ROS for deep tumor therapy. In addition, UCNPs and decomposed Mn 2+ can be used for further upconversion luminescence and magnetic resonance imaging in tumor site. Both in vitro and in vivo experiments demonstrate that this nanoplatform can significantly improve PDT efficiency with tumor imaging capability, which will find great potential in the fight against tumor.