A one-pot isothermal Fluorogenic Mango II arrays-based assay for label-free detection of miRNA

The capability to detect a small number of miRNAs in clinical samples with simplicity, selectivity, and sensitivity is immensely valuable, yet it remains a daunting task. Here, we described a novel Mango II aptamers-based sensor for the one-pot, sensitive and specific detection of miRNAs. Target miRNA-initiated mediated catalyzed hairpin assembly (CHA) would allow for the production of plenty of DNA duplexes and the formation of the complete T7 promoter, motivating the rolling circle transcription (RCT). Then, the subsequent RCT process efficiently generates a huge number of repeating RNA Mango II aptamers, brightened by the incorporation of fluorescent dye TO1-B for miRNA quantification, realizing label-free and high signal-to-background ratio. Moreover, this assay possesses a remarkable ability to confer high selectivity, enabling the distinction of miRNAs among family members with mere 1- or 2- nucleotide (nt) differences. By employing the proposed assay, we have successfully achieved a sensitive evaluation of miR-21 content in diverse cell lines and clinical serum samples. This offers a versatile approach for the sensitive assay of miRNA biomarkers in molecular diagnosis.