Electrochemiluminescence based determination of micro-RNA using target-guided assembly of gold nanoparticles on an electrode modified with Nafion, carbon nanotubes and polyvinylpyrrolidone

The authors describe a sensing interface that is capable of selectively adsorbing gold nanopartices (AuNPs). It was applied to electrochemiluminescent (ECL) detection of microRNA (miRNA). The AuNPs are used as signal transduction probes and luminol acts as the ECL reagent. The sensing interface was generated by sequential assembly of Nafion-carbon nanotubes (CNTs) and polyvinylpyrrolidone (PVP) at a glassy carbon electrode (GCE). If only ss-DNA probes and AuNPs are present, the interaction between them leads to the formation of ss-DNA-capped AuNPs. In this case, the capped-AuNP do not assemble at the interface of the modified electrode. As a result, the ECL is weak due to the poor electroconductivity of PVP. Conversely, if ss-DNA probes bind to target miRNA, the AuNPs can't interact with the DNA/miRNA hybrids formed because of its rigid structure. Hence, aggregated-AuNP are generated. These are concentrated in the sensing interface due to the strong interaction between AuNP and PVP assembled at the modified electrode surface via Au-N chemical bonds. The AuNP concentrated at the surface of the modified GCE electrocatalyze the oxidation of luminol which results in strong ECL. These findings were used to design a quantitative assay for trace levels of miRNA. To confirm the viability of the method, let-7a was used as a model analyte. Under the optimal conditions, the resulting calibration plot is linear in the 40 fM. to 1.0 pM concentration range with a detection limit as low as 20 fM. The method is even capable of discriminating most let-7 miRNA family members and was successfully applied to real sample assay. In our perception, the results demonstrate that this sensing interface represents a cost-effective and sensitive tool for determination of clinically relevant cancer biomarkers.