Amplified electrochemical detection of nucleic acid hybridization via selective preconcentration of unmodified gold nanoparticles

• Differential adsorption ability for single-/double-stranded nucleic acid onto U-AuNP.
• Selective preconcentration of U-AuNPs to mediate amperometric signal.
• Amplified amperometric signal and low background current.
• 105 times improved sensitivity compared to colorimetric method.
• Novel sensing platform with general feasibility.

The common drawback of optical methods for rapid detection of nucleic acid by exploiting the differential affinity of single-/double-stranded nucleic acids for unmodified gold nanoparticles (AuNPs) is its relatively low sensitivity. In this article, on the basis of selective preconcentration of AuNPs unprotected by single-stranded DNA (ssDNA) binding, a novel electrochemical strategy for nucleic acid sequence identification assay has been developed. Through detecting the redox signal mediated by AuNPs on 1, 6-hexanedithiol blocked gold electrode, the proposed method is able to ensure substantial signal amplification and a low background current. This strategy is demonstrated for quantitative analysis of the target microRNA (let-7a) in human breast adenocarcinoma cells, and a detection limit of 16 fM is readily achieved with desirable specificity and sensitivity. These results indicate that the selective preconcentration of AuNPs for electrochemical signal readout can offer a promising platform for the detection of specific nucleic acid sequence.

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