Facile detection of microRNA based on phosphorescence resonance energy transfer and duplex-specific nuclease-assisted signal amplification.

MicroRNAs (miRNAs) play an important role in many biological processes, and its level in plasma and other biological fluids is closely related to many diseases. In this work, a selective room-temperature phosphorescence (RTP) detection method for miRNA was developed based on a duplex-specific nuclease (DSN) -assisted signal amplification strategy and phosphorescence resonance energy transfer (PRET) between poly-diallyldimethylammonium chloride-modified quantum dots (QDs@PDDA) and 6-carboxy-X-rhodamine-modified miRNA sequences complementary oligonucleotide (ROX-ssDNA). The positively charged QDs@PDDA could adsorb negatively charged ROX-ssDNA by electrostatic interaction, whereas the RTP signal of QDs@PDDA could be efficiently quenched by ROX-ssDNA via PRET. In the presence of microRNA-21 (miR-21) and DSN, miR-21 hybridized with ROX-ssDNA initially to form a DNA-RNA heteroduplex as the substrate of DSN, then ssDNA in DNA-RNA heteroduplex would be cleaved into small fragments by DSN and liberate miR-21 to hybridize with another ROX-ssDNA. Eventually, due to weak interaction between ROX-ssDNA fragments and QDs@PDDA, PRET efficiency continually decreased whereas the RTP signal was significantly amplified. By employing the strategy above, quantitative detection of miR-21 in the range of 0.25-40 nM with a detection limit of 0.16 nM was realized, showing excellent performance with simplicity, good selectivity and the ability to be a promising method for miRNA detection.