An "Off On" Electrochemiluminescent Biosensor Based on DNAzyme-Assisted Target Recycling and Rolling Circle Amplifications for Ultrasensitive Detection of microRNA

In this study, an off on switching of a dual amplified electrothemilumineseence (ECL) biosensor baSed on Pb2+-induced DNAzyme-assisted target recycling and rolling circle amplification (RCA). was constructed for microRNA detection. First, the primer probe with assistant probe and miRNA formed Y junction which was cleaved with the addition Of Pb2+ to release miRNA. Subsequently, the released miRNA could initiate the next recycling process, leading to the generation of numerous intermediate DNA sequences .(S2). Afterward, bare glassy carbon electrode (GCE) was immersed into HAuCl4 Solution to electrodeposit a Au nanoparticle layer (depAu), followed by the assembly of a hairpin probe (HP). Then, dopamine modified DNA sequence (Si) was employed to hybridize with HP, which switching off the sensing system. This is the first work that employs DA to quench luminol ECL signal, possessing the biosensor ultralow-background signal. Afterward SZ produced by the target recycling process waS loaded onto the prepared electrode to displace SI :and served as an initiator for RCA. With rational design, numerous repeated DNA sequences coupling with hemin to form hemin/G-quadruplex were generated, which could exhibit strongly catalytic toward H2O2) thus amplified the ECL signal and switched ON state of the sensing system. The liner range for miRNA detection was from 1.0 fM to 100 pM with a low detection limit down to 0.3 fM. Moreover, with the high sefiSitivity and specificity induced by the dual signal amplification, the proposed miRNA. biosensor holds great potential for analysis of other interesting tumor markers.