An enzyme-free probe based on G-triplex assisted by silver nanocluster pairs for sensitive detection of microRNA-21

A sensitive ratiometric fluorescence probe based on hybridization chain reaction (HCR) was constructed for sensitive detection of miRNA-21 by using G-triplex and silver nanocluster pairs (AgNC pairs) as an enzyme-free and label-free signal output group. miRNA-21 was used as the primer for the hybridization chain reaction of molecular beacon 1 (MB1) containing the locked G-triplex sequence and molecular beacon 2 (MB2) with intact AgNC pairs at the 5′ and 3′ end activation. The double-stranded product was obtained along with the opening of the G-triplex and the separation of the AgNC pairs. A detection limit of 67 pM and a linear detection range of 0.1–300 nM were obtained for miRNA-21 determination. The proposed strategy enabled the monitoring of miRNA-21 levels in at least three cell lines, indicating that it provided new ideas for detecting miRNA in real samples.