One-Step in Situ Detection of miRNA-21 Expression in Single Cancer Cells Based on Biofunctionalized MoS₂ Nanosheets

Here, we report the one-step in situ detection of targeted miRNAs expression in single living cancer cells via MoS 2 nanosheet-based fluorescence on/off probes. The strategy is based on the folic acid (FA)–poly(ethylene glycol)-functionalized MoS 2 nanosheets with adsorbed dye-labeled single-stranded DNA (ssDNA). Once the nanoprobes are internalized into cancer cells, the hybridization between the probes and target miRNA results in the detachment of dye-labeled ssDNA from MoS 2 nanosheets surface, leading to the green fluorescence recovery. In this nanoprobe, MoS 2 nanosheets offer advantages of high fluorescence quenching efficiency and extremely low toxicity. The FA conjugation could protect the probes and improve cancer cell transfection efficiency. The ability of this nanoprobe for endogenous miRNA detection in single living cancer cells is demonstrated for two types of cancer cells with different miRNA-21 expressions (MCF-7 and Hela cells). This functionalized MoS 2 nanosheet-based nanoprobes could provide a sensitive and real-time detection of intracellular miRNA detection platform.