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    Ultra-Highly Sensitive DNA Detection with Conducting Polymer-Modified Electrodes: Mechanism, Manufacture and Prospects for Rapid e-PCR

    Journal: J. Electrochem. Soc., Volume 169, MAR 1

    Authors: Zhu, Bicheng; Kerr-Philips, Thomas; Al Ghaus, Zahraa; Chan, Eddie Wai Chi; Barker, David; Evans, Clive W.; Williams, David E.; Travas-Sejdic, Jadranka

    Organizations: Auckland UniServices Ltd; MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand

    At low copy number, sequence detection by polymerase chain reaction (PCR) requires up to 30 cycles (amplification 10(9)) to produce a reliably detectable concentration of fluorescently-labelled amplicons. The cycle number and hence detection time is determined by the analytical sensitivity of the detector. Hybridisation of complementary DNA strands to oligonucleotide-modified conducting polymer electrodes yields an increase in the charge transfer resistance for the ferri-ferrocyanide redox couple. We demonstrate sensors using screen-printed carbon electrodes modified with a conducting polymer formed from a monomer pre-functionalised with complementary oligonucleotide, with pM sensitivity for short sequences and aM for bacterial lysate, with a response time-scale of 5 min. The response is due to the variation of electrical resistance within the polymer film. We develop a mechanism based on repulsion from the solution interface of dopant anions by the charge associated with surface-bound DNA. With results for >160 single-use sensors, we formulate a response model based on percolation within a random resistor network and highlight challenges for large-scale manufacture of such sensors. Such sensors used for label-free electrochemical detection for PCR (e-PCR) would decrease the required cycle number from 30 to less than 10 and would offer a much simplified instrument construction. (C) 2022 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.
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