Photoinduced Electron Transfer-Based Fluorescence Quenching Combined with Rolling Circle Amplification for Sensitive Detection of MicroRNA

MicroRNAs (miRNAs) detection is crucial for further understanding the biological functions of miRNAs and early cancer diagnosis and therapeutics, but now remains a great challenge. Here, we present a novel homogenous biosensing strategy for fluorescence detection of miRNA. In this strategy, a preliminary synthesized circular DNA was used as recognition probe for hybridization with miRNA target, and then miRNA target primed a rolling circle amplification (RCA) reaction. The RCA product could be hybridized with thousands of carboxyfluorescein (FAM)-labeled linear DNA probes, which led FAM to be close to -GGG- base of RCA product, accompanying with the significant fluorescence quenching due to photoinduced electron transfer (PET) between FAM and guanine. This is for the first time to integrate RCA and PET into one detection process. With highly efficient amplification of RCA and excellent signal readout of PET, this method exhibited a high sensitivity toward target miRNA with a detection limit of 6 aM. The targetdependent circularization of the padlock probe and the ligation reaction could improve the specificity effectively, leading to discrimination between miRNA family members. This method provides a simple, isothermal, and low-cost approach for sensitive detection of miRNA and holds great potential for early diagnosis in gene-related diseases.