A fluorescence assay for microRNA let-7a by a double-stranded DNA modified gold nanoparticle nanoprobe combined with graphene oxide.

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 π-π 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.