Precise spatial imaging of microRNAs distribution from single living cells

Accurate analysis of the spatial information of microRNAs (miRNAs) in migrating cells is challenging but also extremely significant for deciphering the molecular mechanisms involved in cancer progression and metastasis. In this work, a non-enzyme-assisted signal amplification sensing strategy was designed to achieve high-resolution imaging of miRNAs in individual migrating cells using a single-molecule fluorescence protocol. As proof of concept, miRNA let-7a was detected at the femtomolar level in vitro with accurate visualization and specificity. Next, the three-dimensional distribution of let-7a in single living cells was precisely visualized using a single -molecule imaging platform, during which the differential expression of intracellular let-7a was monitored. Significantly, the spatially resolved distribution of let-7a was further explored in cells undergoing distinct migration modes, which were induced by confined microenvironments. These results revealed that fast migration modes showed low let-7a expression. This work demonstrated an intuitive and ultrasensitive method of analyzing the spatial distribution of miRNAs in vitro, providing a new perspective for exploring regulatory mechanisms of key molecules in crowded intracellular environments in vivo.