Fluorescence and SERS Imaging for the Simultaneous Absolute Quantification of Multiple miRNAs in Living Cells.

The simultaneous imaging and quantification of multiple intracellular microRNAs (miRNAs) are particularly desirable for the early diagnosis of cancers. However, simultaneous direct imaging with absolute quantification of multiple intracellular RNAs remains a great challenge, particularly for miRNAs, which have significantly different expression levels in living cells. We designed dual-signal switchable (DSS) nanoprobes using the fluorescence-Raman signal switch. The intracellular uptake and dynamic behaviors of the probe are monitored by its fluorescence signal. Meanwhile, real-time quantitative detection of multiple miRNAs is made possible by measurements of the surface-enhanced Raman spectroscopy (SERS) ratios. Moreover, the signal 1:n ratio amplification mode only responds to low-abundance miRNA (asymmetric signal amplification mode) for simultaneous visualization and quantitative detection of significantly different levels of miRNAs in living cells. miR-21 and miR-203 were successfully detected in living MCF-7 cells, in agreement with in vitro results from the same batch of cell lysates. The reported dual-spectrum imaging method promises to offer a new strategy for the intracellular imaging and detection of various types of biomolecules.