A cathodic photoelectrochemical biosensor based on CRISPR/Cas12a trans-cleavage mediated p-n heterojunction quenching mode for microRNA determination

In this study, a cathodic photoelectrochemical (PEC) bioanalysis for sensitive determination of microRNA (miRNA) has been constructed based on CRISPR/Cas12a trans-cleavage mediated [(C6)2Ir(dcbpy)]+PF6− (C6 represents coumarin-6 and dcbpy represents 4,4′-dicarboxyl-2,2′-bipyridine)-sensitized NiO photocathode and p-n heterojunction quenching mode. The [(C6)2Ir(dcbpy)]+PF6−-sensitized NiO photocathode exhibits a stable and dramatically improved photocurrent signal due to highly effective photosensitization of [(C6)2Ir(dcbpy)]+ PF6−. Then Bi2S3 quantum dots (Bi2S3 QDs) is captured on the photocathode, resulting in markedly quenching of the photocurrent. When target miRNA is specifically recognized by the hairpin DNA to stimulate the trans-cleavage activity of CRISPR/Cas12a, leading to the leave of the Bi2S3 QDs. The photocurrent is gradually recovered with the increasing target concentration. Thus, the quantitative signal response to target is achieved. Benefiting from excellent performance of NiO photocathode, intense quenching effect of p-n heterojunction and accurate recognition ability of CRISPR/Cas12a, the cathodic PEC biosensor shows a wider linear range over 0.1 fM–10 nM, with a low detection limit of 36 aM. Also, the biosensor exhibits satisfying stability and selectivity.