Ultrasensitive detection of microRNA with isothermal amplification and a time-resolved fluorescence sensor

MicroRNAs (miRNAs) play important roles in a plethora of biological and cellular processes. The levels of miRNAs can be useful biomarkers for cellular events or disease diagnosis, thus the method for sensitive and selective detection of miRNAs is imperative to miRNA discovery, study, and clinical diagnosis. Here we develop a novel method to quantify miRNA expression levels as low as attomolar sensitivity by two-stage exponential amplification reaction (EXPAR) and a time-resolved fluorescence sensor in real samples. The method reveals superior sensitivity with a detection limit of miRNA of 0.1 aM under pure conditions. The method also shows the high selectivity for discriminating differences between miRNA family members, thus providing a promising alternative to standard approaches for quantitative detection of miRNA.