Quantitative and specific detection of cancer-related microRNAs in living cells using surface-enhanced Raman scattering imaging based on hairpin DNA-functionalized gold nanocages
Variations in the intracellular expression level of cancer-related miroRNAs (miRNAs) were connected with worsening tumor progression. A simple, accurate, and sensitive analytical method for imaging and detection of intracellular miRNA was still a great challenge due to low abundances of miRNAs and the complexity of intracellular environments. In this work, a target miRNA (miRNA)-mediated catalytic hairpin assembly (CHA)-induced gold nanocages (GNCs)-hairpin DNA1 (hpDNA1)-hpDNA2-GNCs nanostructures were designed for surface-enhanced Raman scattering (SERS) detection and imaging of the specific miR-125a-5p in normal lung epithelial cell line (BEAS-2B cells) and lung cancer cell line (A549 cells). The finite difference time domain (FDTD) simulations showed that the polymer of GNCs owned much stronger electromagnetic field in nanogaps than that of single GNC, theoretically confirming the rational design of CHA assembly strategy. Using this method, miR-125a-5p can be detected in a wide linear range with a detection limit of 4.375 aM and high selectivity over other miRNAs in vitro. Moreover, SERS imaging successfully detected and distinguished the expression levels of intracellular miR-125a-5p in BEAS-2B cells and A549 cells. The results obtained by the SERS assay were consisted with real-time quantitative polymerase chain reaction (qRT-PCR). This method can offer a powerful strategy for imaging and quantitative detection of various types of biomolecules in vitro as well as in living cells.