Chameleon silver nanoclusters for ratiometric sensing of miRNA

Chameleon silver nanoclusters (AgNCs) have attracted substantial attention over traditional AgNCs, which provide new possibilities for the construction of ratiometric fluorescent biosensors. Herein, a novel method for sensitive and selective detection of miRNA is developed coupling chameleon AgNCs with hybridization chain reaction. Generally, the signal DNA probe is designed to contain two pieces of DNA templates for the synthesis of AgNCs, which are in close proximity due to the hairpin structure. A series of hybridization reactions can be triggered by target miRNA, which open the hairpin of signal probe and separate the two pieces of segmental AgNCs. Controllable color switching from red to yellow is thus achieved. Note that signal generation and amplification are integrated into one step, which is a great advance compared with previous amplified systems. The proposed strategy provides a sensitive fluorescent detection of miRNA down to 2.8 pM with high selectivity. Therefore, this work not only brings novel insights into fluorescence regulation of DNA-templated AgNCs, but also holds great potential for the application of miRNA diagnostics.