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 is observed, and the limit of detection (LOD) was determined to be 0.011 amol/ng. The luminescence data show a linear response between 0.6 × 10 and 31 × 10 IU for logarithmic concentration of intracellular telomerase with a LOD of 3.2 × 10 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.

Assemblies of nanomaterials for biological applications in living cells have attracted much attention. Herein, graphene oxide (GO)-gold nanoparticle (Au NP) assemblies are driven by a splint DNA strand, which is designed with two regions at both ends that are complementary with the DNA sequence anchored on the surface of the GO and the Au NPs. In the presence of microRNA (miR)-21 and epithelial cell-adhesion molecule (EpCAM), the hybridization of miR-21 with a molecular probe leads to the separation of 6-fluorescein-phosphoramidite-modified Au NPs from GO, resulting in a decrease in the Raman signal, while EpCAM recognition reduces circular dichroism (CD) signals. The CD signals reverse from negative in original assemblies into positive when reacted with cells, which correlates with two enantiomer geometries. The EpCAM detection has a good linear range of 8.47-74.78 pg mL and a limit of detection (LOD) of 3.63 pg mL , whereas miR-21 detection displays an outstanding linear range of 0.07-13.68 amol ng and LOD of 0.03 amol ng . All the results are in good agreement with those of the Raman and confocal bioimaging. The strategy opens up an avenue to allow the highly accurate and reliable diagnosis (dual targets) of clinic diseases.

A DNA-driven gold (Au) heterodimer for intracellular telomerase detection is fabricated. The highly biocompatible and intracellularly stable probe shows an active chiroptical property in the visible region, due to the scissor-like confi guration formed by prolate nanoparticles. Importantly, the telomerase activity is specifi cally quantifi ed using circular dichroism intensity in situ after internalization of the heterodimer into cancer cells. Moreover, the results clearly illustrate that this method has a remarkable linear range from 0.8 × 10 −12 to 32 × 10 −12 IU, and the limit of detection for telomerase activity is 1.7 × 10 −15 IU in a single HeLa cell. This strategy paves the way for chirality-based ultrasensitive detection of intracellular cancer markers.