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

Abstract

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 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.

Advances and challenges in conventional and modern techniques for halal food authentication: A review

“…In PCR, specially designed primers amplify a specific target sequence (Table 3 ). In addition, the incorporation of an internal hybridization probe can improve the specificity and sensitivity of PCR (Zhu et al., 2022 ). This strategy is fast and specific to detect species adulteration with prohibited or nonhalal foods or ingredients.…”