Hairpin DNA probe with 5′-TCC/CCC-3′ overhangs for the creation of silver nanoclusters and miRNA assay

A facile strategy for the assay of target miRNA using fluorescent silver nanoclusters (AgNCs) has been described. Due to the preferable interaction between cytosine residues and Ag+, a short cytosine-rich oligonucleotide (ODN) with only six bases 5 '-TCCCCC-3 ' served as an efficient scaffold for the creation of the AgNCs. The AgNCs displayed a bright red emission when excited at 545 nm. Such ODN base-stabilized AgNCs have been exploited for miRNA sensing. Overhangs of TCC at the 5 ' end (5 '-TCC) and CCC at the 3 ' end (CCC-3 ') (denoted as 5 '-TCC/CCC-3 ') appended to the hairpin ODN probe which also contains recognition sequences for target miRNA were included. Interestingly, the AgNCs/hairpin ODN probe showed similar spectral properties as that templated by 5 '-TCCCCC-3 '. The formation of the hairpin ODN probe/miRNA duplex separated the 5 '-TCC/CCC-3 ' overhangs, thus disturbing the optical property or structure of the AgNCs. As a result, fluorescence quenching of the AgNCs/hairpin ODN probe was obtained, which allows for facile determination of target miRNA. The proposed method is simple and cost-effective, holding great promise for clinical applications. (C) 2013 Elsevier B.V. All rights reserved.