Dual-Modal FeCuSe and Upconversion Nanoparticle Assemblies for Intracellular MicroRNA-21 Detection.

In situ quantification and imaging of low-level intracellular microRNAs (miRs) are important areas in biosensor research. Herein, DNA-driven FeCuSe@upconversion nanoparticle (UCNP) core@satellite nanostructures were developed to probe microRNA-21 (miR-21). FeCuSe@UCNP probes displayed dual signals: upconversion luminescence (UCL) and magnetic resonance imaging (MRI). In the presence of miR-21, the luminescence signal was restored and the value was significantly increased because of dissociation of UCNPs from the assemblies. There was a good linear relationship between the dual signals and the expression levels of miR-21 in the range of 0.035-31.824 amol/ng. The limit of detection (LOD) was 0.0058 amol/ng for the luminescence intensity and 0.0182 amol/ng for the MRI signal. This method opens a new avenue for intracellular miR-21 detection with high sensitivity and specificity.