Simultaneously electrochemical detection of microRNAs based on multifunctional magnetic nanoparticles probe coupling with hybridization chain reaction

We report a sensor combining two distinguishable magnetic nanoprobes (DNAl/Fe3O4 NPs/Thi and DNA2/Fe3O4 NPs/Fc) with target-triggered hybridization chain reaction (HCR) strategy for the simultaneous detection of microRNA-141 (miR-141) and microRNA-21 (miR-21). In the presence of targets, the thiol-modified hairpin capture probes (HCP1 and HCP2) specifically hybridize with miR-141 and miR-21 on a gold electrode, leading to the conformation change of HCP1 and HCP2, respectively. The conformation change subsequently triggers HCR to generate plentiful bonding sequences of magnetic nanoprobes. Thus, numerous thionine (Thi) modified DNA1/Fe3O4 NPs/Thi and ferrocene carboxaldehyde (Fc-CHO) modified DNA2/Fe3O4 NPs/Fc are captured by the well-designed HCR, via DNA hybridization respectively, giving rise to the dual magnified response of currents. The increase in the electrochemical currents at different potentials of the two magnetic nanoprobes enables us to simultaneously and quantitatively detect miR-141 and miR-21. Target-triggered HCR increases the amount of captured nanoprobes due to the increasing number of bonding sequences, greatly amplifying the currents of the two magnetic nanoprobes in the presence of targets, and ultimately realizing the dual signal amplification with increased sensitivity. The sensor can be applied for detecting miRNAs in cell lysates, thus, promising to be a clinic diagnosis of cancers by means of simultaneous detection of a variety of miRNA biomarkers.