Quantum dot nanoconjugates for immuno-detection of circulating cell-free miRNAs

Argonaute protein (AGO2) bound circulating cell-free miRNAs (ccf-miRs), in the recent years, has attracted great attention due to their differential abundance in biological fluids. In the present work, a selective and technically uncomplicated quantum dot (QD) nanoconjugate has been fabricated combining the specific affinity of the antibody and fluorescent property of QDs for the precise immuno-detection of AGO2-bound ccf-miRs in plasma samples. The electrophoretic mobility assay confirmed the conjugation of antibody with QDs. The detection methodology involves a highly specific antigen-antibody reaction between the AGO2 proteins of miRNA-induced silencing complex and the anti-AGO2 antibody conjugated with QDs. The recognition efficiency of QD-Ab nanoconjugates was analysed using flow cytometry and fluorometry. The flow cytometry results demonstrated a significant change in the fluorescence intensity of the prepared nanoconjugates upon capture of ccf-miRs in the plasma samples with respect to the samples devoid of any miRNAs. Fluorometry measurements exhibited corroboration with the flow cytometry results indicating the selectivity and reproducibility of the developed method. Current research highlights the translational significance of the methodology as a novel flow cytometry based immunoassay for detection of differentially expressed AGO2-bound miRNAs in clinical and field settings.