Bifunctional MXene quantum dots-coated bimetallic Prussian blue analogues for sensitive sensing and accurate localization imaging of miRNAs in living cells.

MicroRNAs (miRNAs) are involved in multiple cellular processes and play a critical role in clinical diagnosis. In-situ spatiotemporal imaging of miRNAs in living cells is tightly linked to the carcinogenesis and development of malignant tumors. Herein, we proposed a bifunctional nanosystem-based MXene quantum dots-coated bimetallic Prussian blue analogues (Co-Mn PBA@MQDs) to execute in-vitro sensing and intracellular imaging of miRNA in living cells. The 3D nanostructures of Co-Mn PBAs were regulated to slow down the coordination reaction rate by controlling the diffusion of metal clusters and ligand precursors, thereby anchoring MQDs as the carriers of DNA probes. The resulting Co-Mn PBA@MQDs nanoparticles with miRNA recognition ability exhibit excellent electrocatalytic and photoluminescence properties for target miRNA analysis. It reached miRNA detection limit of 0.37 fM (S/N = 3) with a wide linear range of 1 fM to 1 nM, and allowed distinguish family members without additional complex modifications. Meanwhile, DNA probe adsorbed on Co-Mn PBA@MQDs can provide delivery capacity for intracellular miRNA location, resulting in the in-situ monitoring and imaging of miRNA with deregulated expression levels in cancer cells. With these advantages, the developed strategy provides a paradigm for the rational design of the miRNA analysis system, which is expected to be widely applied to disease diagnosis and further theragnostic fields.