Peptide nucleic acid-based electrochemical biosensor for simultaneous detection of multiple microRNAs from cancer cells with catalytic hairpin assembly amplification

Herein we demonstrated a facile electrochemical method for simultaneous detection of miRNA21 and miRNA155 using a peptide nucleic acids (PNAs)-modified gold electrode coupled with the target-catalyzed hairpin assembly (CHA) strategy. In the presence of the target miRNA, the CHA was triggered selectively between two hairpins with one ferrocene (Fc) or methylene blue (MB) labelled. The resulting redox-active group modified CHA products (Fc-CHA21 or MB-CHA155) were then specifically captured by the PNA probes (PNA21 or PNA155) attached on the surface of a gold electrode, which bring the Fc and MB labels into close proximity to generate apparently enhanced electrochemical signals for sensitive and simultaneous detecting of low amount miRNA21 and miRNA155 in cancer cells. This assay was highly selective for discriminating miRNAs with similar sequences and has detection limits of 2.49 fM and 11.63 fM for miRNA21 and miRNA155, respectively. The feasibility of the method for sensitive determination of miRNA21 and miRNA155 from human cancer cells was also demonstrated. This method thus has great potential to be applied for simultaneous detecting of a variety of miRNA biomarkers for clinic applications due to its simple, sensitive and accurate features.