Attomolar ultrasensitive microRNA detection by DNA-scaffolded silver-nanocluster probe based on isothermal amplification

MicroRNAs (miRNAs) play vital 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 target-assisted isothermal exponential amplification coupled with fluorescent DNA-scaffolded AgNCs and demonstrated its feasibility in the application of detecting miRNA in real samples. The method reveals superior sensitivity with a detection limit of miRNA of 2 aM synthetic spike-in target miRNA under pure conditions (approximately 15 copies of a miRNA molecule in a volume of 10 μL) and can detect at least a 10 aM spike-in target miRNA in cell lysates. 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. This simple and cost-effective strategy has a potential of becoming the major tool for simultaneous quantitative analysis of multiple miRNAs (biomarkers) in tissues or cells and supplies valuable information for biomedical research and clinical early diagnosis.