Novel PNA-based diagnostics for microRNA detection

We propose development of chemically-modified electrodes as the detection element of a novel bioanalytical scheme of broad potential applicability. Tumour-derived microRNAs (miRNAs) are emerging as novel biomarkers for the diagnosis and prognosis of human cancers. We aim to develop an ultrasensitive and minimally invasive electrochemical technology for the screening of multiple miRNAs in body fluids (e.g. serum, plasma or urine).
Ladame has demonstrated a novel fluorescence-based sensing strategy for detecting miRNAs in various biological fluids. It uses a combination of two complementary hybridization probes based on a synthetic peptide nucleic acid (PNA) scaffold. PNAs show higher binding affinity, specificity and chemical robustness than DNA or RNA probes making them attractive for application in diagnostics. Simultaneous binding of both probes leads to a Michael-type addition of a thiol from one probe to the quenched coumarin on the second probe, leading to restoration of the fluorescence signal. Herein we propose extension of this technology to electrochemical detection by exploiting 1,4-additions to electrochemically generated quinoid moieties. This offers the advantage of direct control of the RNA-templated reaction for improved selectivity. Since electrochemical methods scale well to extreme miniaturization our strategy holds out the prospect of multiplexed sensing.