Hybridization Chain Reaction-Mediated Luminescent Silver Nanocluster System for Amplified Detection of miRNA-21

MicroRNAs (miRNAs) are biomarkers and potential therapeutic targets for various diseases. It is important to develop convenient and sensitive methods for miRNAs analysis. Herein, by integrating the high signal amplification capability of hybridization chain reaction (HCR) and the excellent luminescence performance of DNA-templated silver nanoclusters (DNA-AgNCs), a versatile and label-free fluorescent sensor was constructed for highly sensitive miRNA-21 detection. First of all, the DNA template for synthesizing AgNCs was blocked in the hairpin DNA for HCR assembly. Addition of the target DNA could trigger self-assembly of hairpin DNAs, and release numerous free DNA template for the synthesis of near-infrared fluorescent AgNCs. The fluorescence intensity of AgNCs was positively correlated with concentration of trigger DNA. Furthermore, by introducing an auxiliary hairpin containing a blocked HCR initiator sequence, the HCR-AgNCs system could be adapted as a universal sensing platform for target detection. Taking miRNA-21 analysis as an example, in the presence of miRNA-21, the auxiliary hairpin could be opened, releasing the free trigger DNA sequence for HCR, which in turn initiated the HCR reaction and the following synthesis of AgNCs. The results showed that the linear range of this method for miRNA-21 detection was from 250 pmol/L to 8 nmol/L, and the detection limit was as low as 19. 9 pmol/ L (3 sigma/S). The HCR-AgNCs system was label. free, sensitive and extendable, which could be used as a universal sensing platform for analyzing different types of targets. This approach may provide a practical method for clinical diagnosis of biomarkers.