Simple and sensitive detection of microRNA based on guanine-rich DNA-enhanced fluorescence of DNA-templated silver clusters

Based on the enhancement of fluorescence of DNA-templated silver clusters (AgNCs) by guanine-rich DNA combined with duplex-specific nuclease-assisted signal amplification (DSNSA), a very simple and sensitive homogeneous strategy for microRNA (miRNA) detection has been established. The experiment design is straightforward. One DNA probe, one AgNCs, and one nuclease can complete the whole process of amplification, signal transmission, and output. The capture DNA probe containing a rich guanine sequence binds to the sticky DNA terminal of the dark AgNCs, narrowing the distance between the guanine bases and the AgNCs, lighting up the fluorescence of the AgNCs. Target miRNA-let-7a can hybridize with the 5′ terminal of the capture DNA probe and initiate the DSNSA reaction. The DSNSA reaction degrades the capture DNA probe, generating many guanine-rich DNA fragments. The released guanine-rich DNA fragments can not bind to AgNCs through hybridization. The fluorescence of the AgNCs can not be enhanced. As the dosage of let-7a increases, the fluorescence signal decreases gradually. The proposed method achieves excellent sensitivity (detection limit is 80 amol let-7a) and more than four orders of magnitude dynamic detection range. • Simplicity of design: a capture DNA probe, a DNA-templated AgNCs and a nuclease complete the whole process of the signal amplification, transmission, and output. • The proposed method exhibits excellent sensitivity and selectivity. Its detection limit is low as 80 amol let-7a. It can distinguish one base difference in target miRNA detection. • The proposed method is applied successfully to detecting let-7a in the Hela cells. • Using DNA-templated AgNCs as fluorescent probes provides a new idea for the miRNA detection.