Sensitive electrochemical determination of miRNAs based on a sandwich assay onto magnetic microcarriers and hybridization chain reaction amplification.

A novel electrochemical approach for determination of miRNAs involving a sandwich hybridization assay onto streptavidin-magnetic beads (Strep-MBs), hybridization chain reaction (HCR) amplification and amperometric detection at disposable screen-printed carbon electrodes is reported. Using miRNA-21 as the target analyte, a dynamic linear range from 0.2 to 5.0nM with a 60pM (1.5fmol in 25µL) detection limit was obtained. The achieved sensitivity is 24-fold higher than a non-HCR amplification approach involving conventional sandwich type assay onto MBs. Moreover, the whole assay time lasted 1h 45min which is remarkably shorter than other reported methodologies. The methodology exhibited full selectivity against other non-complementary miRNAs as well as an acceptable discrimination between homologous miRNA family members. The applicability of this novel approach was demonstrated by determining mature miRNA-21 in total RNA (RNAt) extracted from tumor cells and human tissues.

Simultaneous detection of two breast cancer-related miRNAs in tumor tissues using p19-based disposable amperometric magnetobiosensing platforms.

A novel magnetobiosensing approach for the rapid and simultaneous detection of two breast cancer-related miRs (miR-21 and miR-205) is reported. It involves the use of antimiR-21 and antimiR-205 specific probes, chitin-modified magnetic beads (Chitin-MBs), the p19 viral protein as capture bioreceptor and amperometric detection with the H2O2/hydroquinone (HQ) system at dual screen-printed carbon electrodes (SPdCEs). The use of SPdCEs allows the simultaneous independent amperometric readout for each target miR to be measured. The magnetosensor exhibited sensitive and selective detection with dynamic ranges from 2.0 to 10.0nM and detection limits of 0.6nM (6fmol) for both target miRs without any amplification step in less than 2h. The usefulness of the approach was evaluated by detecting the endogenous levels of both target miRs in total RNA (RNAt) extracted from metastatic breast cancer cell lines and human tissues.