A multifunctional nano system based on DNA and CeO₂ for intracellular imaging of miRNA and enhancing photodynamic therapy

An increased content of reactive oxygen species (ROS) is a primary feature of tumor cells. When the new homeostasis established by cancer cells with a high ROS level is destroyed, this leads to oxidative stress and apoptosis. In this study, a composite nanosystem was designed in which the DNA structure with the functions of miRNA detection and drug delivery is connected to CeO₂ nanoclusters that exhibit enzyme-like activity to enable them to load drugs together. In addition, based on the concept of sequential catalysis, we used CeO₂ to decompose H₂O₂ into O₂ with low cytotoxicity, which provides raw materials for the photodynamic therapy (PDT) of the Cy5 fluorescent group modified on the DNA. Subsequently, this is transformed into highly cytotoxic free radicals ([rad]OH), and we used PDT to further stimulate the therapeutic ability of doxorubicin (DOX) to improve its effectiveness in killing cancer cells. This composite nanosystem can perform fluorescence detection for miRNA-21 in vitro, intracellular fluorescence imaging, and PDT treatment, and can enhance the effect of DOX.