microRNA (miRNA) has drawn a great attention in biomedical research due to its functions on biological processes. Detection of miRNAs is a big challenge since the amount present in real samples is very low and the length of them is short. In this study, for the first time an electrochemical biosensor for detection of mir21 using the oxidation signal of protein 19 (p19) as a molecular caliper was designed. The proposed method enables detection of mir21 in direct, rapid, sensitive, inexpensive and label-free way. Binding specificity of the p19 to 20-23 base pair length double stranded RNA (dsRNA) and direct/water-mediated intermolecular contacts between the fusion protein and miRNA allows detection of miRNA-antimiRNA hybrid structure. The detection of mir21 was achieved in picomole sensitivity through the changes of intrinsic p19 oxidation signals observed at +0.80 V with Differential Pulse Voltammetry (DPV) and the specifity of the designed sensor was proved by control studies.
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