Abstract
DNA-scaffolded silver nanoclusters (DNA/AgNC) probes are widely used to detect microRNAs (miRNAs) for diagnosing diseases. However, current available DNA/AgNC probes, which primarily based on fluorescence quenching (turn-off) method, suffer from low detection accuracy caused by bio-matrix interferences. Herein, we designed a new DNA/AgNC-cDNA probe to detect miRNA based on a fluorescence enhancing (turn-on) strategy. Using miR-223, a potential biomarker of inflammatory bowel diseases (IBD), as the target miRNA, we devised the partially hybridized DNA/AgNC-cDNA fluorescent probe. The cDNA was the sequence that completely paired against miR-223 and served as a quencher to the fluorescent DNA/AgNC moiety. Upon the presence of miR-223, which could competitively bind the cDNA, then the DNA/AgNC was set free from the DNA/AgNC-cDNA complex accompanied by an increase in the fluorescence of the DNA/AgNC. Further, by fluorescence decay and polyacrylamide gel electrophoresis (PAGE) experiments, we tentatively addressed the probe working mechanism: the restriction of photo-induced electron-transfer from complementary nucleobases to DNA/AgNC. Compared with the traditional fluorescence turn-off approach, our newly designed probe significantly improved the sensitivity (10 times) and demonstrated excellent specificity. This rapid, label-free, and low-cost fluorescence enhancing method can potentially be applied in the diagnosis of miR-223 associated disease, such as IBD.