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

• Main Authors: Barker, D. (Author), Chan, E.W.C (Author), Evans, C.W (Author), Ghaus, Z.A (Author), Kerr-Philips, T. (Author), Travas-Sejdic, J. (Author), Williams, D.E (Author), Zhu, B. (Author)
• Format: Article
• Language: English
• Published: IOP Publishing Ltd 2022
• Subjects: Amplicons; Charge transfer; Chemical detection; Conducting polymers; Copy number; Cycle number; Detection time; DNA; DNA detection; ELectrochemical detection; Electrode mechanism; Electrodes; Hybridisation; Oligonucleotides; Polymer films; Polymer modified electrodes; Polymerase chain reaction; Semiconducting films; Sequence detection; Solvents
• Online Access: View Fulltext in Publisher

 At low copy number, sequence detection by polymerase chain reaction (PCR) requires up to 30 cycles (amplification 109) 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 prefunctionalised 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. © 2022 The Electrochemical Society ("ECS").