The direct catalytic synthesis of ultrasmall Cu2O-coordinated carbon nitrides on ceria for multimodal antitumor therapy

Engineering chem-/sono-/photo-multimodal antitumor therapies has become an efficient strategy to combat malignant tumors. However, the existence of hypoxia in the tumor microenvironment (TME) leads to limited sonodynamic or photodynamic efficiency because O2 is the key reactant during the process of generation of reactive oxygen species (ROS). Here, to design a desirable platform that can simultaneously convert H2O2 in the TME into ROS and O2 for efficient chem-/sono-/photo-multimodal tumor therapies, we have created ultrasmall Cu2O-coordinated carbon nitride on a biocompatible ceria substrate (denoted as Cu2O-CNx@CeO2) via a self-assisted catalytic growth strategy. The chemical and morphological structures, ROS and O2 generation activities, and chemo-/photo-/sono-dynamic specificities of Cu2O-CNx@CeO2 when serving as multifunctional biocatalytic agents were systematically disclosed. The experimental studies validated that Cu2O-CNx@CeO2 presents state-of-the-art peroxidase-like and catalase-like activities. Moreover, the light excitation and ultrasound irradiation were also demonstrated to boost ROS production. The in vitro and in vivo experiments suggest that Cu2O-CNx@CeO2 can efficiently inhibit the growth of malignant melanoma via chem-/sono-/photo-multimodal antitumor ability. We believe that applying these new biocatalysts with dual catalytic activities of producing ROS and O2 will offer a new path for engineering multimodal nanoagents to combat malignant tumors.