Ratiometric fluorescence biosensing of silver NanoCluster Beacons for ATP detection based on ligation- triggered rolling cycle amplification

NanoCluster Beacon (NCB) provided a label-free ratiometric fluorescence method with obvious dual-color signal output. In this work, a novel method was developed for ATP detection by coupling NCB and rolling cycle amplification (RCA). NCB was composed of the silver clusters (P2-AgNCs) and the converter (P3), and the linker sequence (P1) kept them in close proximity by Watson-Crick base pairing. The fluorescence performance of NCB was correlated with the status of the AgNCs. Controllable color switching from green to red was thus achieved. ATP served as cofactor of T4 DNA ligase to catalyze the ligation reaction, then the subsequent RCA reaction produced a long-stranded linear DNA with a lot of P1 sequences that assembled with NCBs. So that the green fluorescence of AgNCs (λem = 542 nm) was transformed to bright red fluorescence (λem = 630 nm), lighting up the ratiometric fluorescence of NCBs. Under the optimized conditions, the value of F630 nm/F542 nm (F630/542) was linearly correlated with the logarithmic ATP concentration with a detection limit of 122 pM. Furthermore, the proposed method showed good performance in human serums, indicating its potential to be applied in clinical diagnosis.