Dual Quantification of MicroRNAs and Telomerase in Living Cells

The development of a unique and universal strategy for the simultaneous quantification of different types of biomolecules (i.e., nucleic acids and proteins) in living cells is extremely challenging. Herein, a two-signal platform, based upon surface-enhanced Raman scattering and upconversion, for the ultrasensitive and quantitative in situ detection of microRNA (miR)-21 and telomerase in living cells is reported. In the presence of miR-21 and telomerase, the hybridization of miR-21 with a molecular beacon leads to the separation of 3,3'-diethylthiocarbamyl cyanine iodide-modified Au NR dimers, resulting in a decrease in Raman signal. Also, the target telomerase triggers elongation of the telomerase primer strands, followed by substitutional hybridization and release of upconversion nanoparticles, leading to an increase in luminescence. A linear relationship between the Raman intensities and logarithmic concentration of intracellular miR-21 between 0.021 and 22.36 amol/ng_RNA is observed, and the limit of detection (LOD) was determined to be 0.011 amol/ng_RNA. The luminescence data show a linear response between 0.6 × 10^-12 and 31 × 10^-12 IU for logarithmic concentration of intracellular telomerase with a LOD of 3.2 × 10^-13 IU. These results are in good agreement with Raman and confocal imaging. Importantly, the ultrasensitive detection of miR-21 was possible due to strong plasmonic "hot spots". This innovative two-signal approach can be utilized for the quantitative and precise detection of many types of signaling molecules in living cells and to understand the chemistry within cellular systems and its application in the diagnosis of disease.