Hybridization induced ion-barrier effect for the label-free and sensitive electrochemical sensing of Hepatocellular Carcinoma biomarker of miRNA-122

A label-free and sensitive electrochemical biosensing strategy for a hepatocellular carcinoma biomarker of miRNA-122 has been proposed based on hybridization induced ion-barrier effect on the electroactive sensing interface.First,a bifunctional electroactive electrode with the nanocomposite of Prussian blue(PB) and gold nanoparticles(AuNPs) was prepared through a two-step electrodeposition process.The PB endows the electrode excellent K~+-dependent voltammetric signal and the AuNPs act as the matrix for the self-assembly immobilization of the thiolated probe DNA.Upon specific hybridization of probe DNA with the target miRNA-122,the formed double duplex induced the ion-barrier effect,which blocked the diffusion of the K~+ from the bulk solution to the electrode surface.As a result,the voltammetric signal of the PB on the electrode was surpressed,and thus the target miRNA-122 was monitored.The sensing assay showed that the miRNA-122 could be analyzed in the concentration range from 0.1 fmol/L to 1.0 nmol/L,with a detection limit of 0.021 fmol/L.The practical applicability of the biosensor was also verified by the spiking serum assay.