An electrochemical biosensor for sensitive detection of microRNAs based on target-recycled non-enzymatic amplification

In this study, a simple, economic, and label-free electrochemical biosensor was developed for highly sensitive and selective miR-21 detection based on Fe(CN)(6)(3-)/Fe(CN)(6)(4-) electrochemical signal, which relies on DNA structures conjugating with carboxyl multi-wall carbon nanotubes (MWCNTs-COOH)-modified glassy carbon electrode (GCE). High sensitivity and specificity of the biosensor were achieved by taking advantage of the target-recycled non-enzymatic amplification strategy (TRNEAS), which relies on sequence-specific hairpin strand displacement and does not require the addition of environment-susceptible enzymes. Besides, the SP-DNA strictly binds to the cMWCNTs/GCE via amide bonds, which ensure good electrochemical results and excellent stability for target miRNA detection. The developed miR-21 electrochemical biosensor exhibited a broad linear dynamic range of 0.1 fmol to 5 pmol and a detection limit of 56.7 amol for miR-21 detection in vitro. The relative miR-21 expression levels were particularly detected by our developed miR-21 biosensor and were highly consistent with the stem-loop RT-PCR results. In summary, our developed electrochemical biosensor exhibits great potential for further application in biomedical research and early clinical diagnosis.