Ultra-sensitive detection of microRNA-21 based on duplex-specific nuclease-assisted target recycling and horseradish peroxidase cascading signal amplification

The detection and analysis of microRNA (miRNA) can provide critical information for biomedical research and clinical diagnosis. In this paper, we constructed a simple method to achieve ultra-sensitive and rapid detection of miRNA based on the double-specific nuclease (DSN) assisting target recovery and horseradish peroxidase (HRP) cascading signal amplification. In the existence of target microRNA-21 (miR-21), the DSN enzyme specifically cut the single-stranded DNA (ssDNA) hybridized with the target miRNA but still kept the target miRNA intact, so there were more free HRP released from the polystyrene microparticles-ssDNA-HRP conjugates (PS-ssDNA-HRP) because of the target recycle and signal amplification. The free HRP in the supernatant were collected to react with the substrate 3,3',5,5'-tetramethylbenzidine (TMB). The color and absorbance changes of HRP-TMB system further resulted in qualitative screening by naked eyes and quantitative detection by the microplate reader with the detection limit as low as 3.1 fM. This assay protocol not only showed high sensitivity and selectivity, but also well distinguished the difference between the miRNA family members, as well as the simple operation, fast detection, naked eye qualitative and microplate reader quantification. It has great application value in the biomedical research and clinical diagnosis.