Electrochemical functionalization of polypyrrole nanowires for the development of ultrasensitive biosensors for detecting microRNA

A simple electrochemical patterning strategy has been developed for the construction of ultrasensitive biosensors based on polyethylene glycol (PEG)-polypyrrole (PPy) nanowires substrate in order to supply improved antifouling performances. PPy nanowires array was produced through electrochemical polymerization of pyrrole at constant potential onto glassy carbon electrode (GCE) surface. PPy nanowires surfaces were decorated with 4-armed PEG molecules by electrochemical oxidation of amine groups offered by PEG end chains. The prepared PEG/PPy nanowires have integrated the excellent electrical conductivity of conducting polymer PPy nanowires with the good antifouling property of PEG. MicroRNAs (miRNAs) play very important roles in cancer development and a variety of diseases, which make them become promising biomarkers of the onset, prognosis and risk of diseases. Therefore the establishment of miRNA profiles for diseases and the detection of miRNAs in biological samples are critical milestones in diagnostics. An ultrasensitive electrochemical biosensor for miRNA can be effortlessly developed by the immobilization of DNA probes onto PEG/PPy nanowires. DNA/RNA hybridization was monitored by changes of methylene blue (MB) redox signal using differential pulse voltammetry (DPV) method. A wide linear range (0.10 pM ∼ 1.0 nM) to target miRNA was obtained by the fabricated biosensor, and miRNA mismatches can also be easily identified with satisfactory. Furthermore, the biosensor based on PEG/PPy nanowires can be extended to the development of any type of DNA-based biosensor.