▎ 摘　　要

Graphene oxide (GO) is capable of quenching fluorescence in bound fuel single stranded DNA (ssDNA) labeled with dye. In the presence of target microRNA let-7a, two cascaded toehold-mediated strand displacement reactions (TSDRs) were triggered, thereby desorbing substantial pi-pi stacking adsorbed fuel DNA from GO through recycling amplification, simultaneously accompanied with the restoration of dye fluorescence. By coupling dsDNA-AuNPs with the GO nanosheet, the proposed strategy achieved a non-enzymatic sensitive assay with a low detection limit of 3.9 pM. Hence, the proposed approach has great potential for applications in early cancer diagnosis and clinical analysis.