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 (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.