Multiplexed miRNA detection using cationic polythiophene

Abstract

Detection of short strands of miRNA has significant biomedical and biological implications. We report here the integration of fluorescent conjugated polymers as detection moieties with metallic striped nanorods for multiplexed detection of miR-21 and miR-122 in solution. Specifically, cationic conjugated polymers were used as chemical-coupling-free signal reporters to indicate the presence of specific miRNA molecules in solution and nanorods with self-encoded striping patterns were used as multiplexing assay substrates. A competitive assay format was developed to take advantage of stronger fluorescence output from DNA/DNA duplexes than that from DNA/miRNA duplexes. Upon selection of optimal competing DNA probes, the fluorescence signal collected was inversely proportional to the concentration of target miRNA in the system. A detection limit of fmol amounts of miRNA was achieved, with a linear response spanning across a broad dynamic range. The use of inherently encoded nanorods allowed simultaneous detection of different miRNA targets with good specificity.