Detection of a few DNA copies by real-time electrochemical polymerase chain reaction†
In the current work, accurate quantification over 10 to 108 DNA copies has been successfully achieved for the first time by real-time electrochemical PCR. This has been made possible thanks to the combined use of a fully automated house-built electrochemical qPCR device, optimized for parallel heating and electrochemical monitoring of up to 48 PCR solutions, and the appropriate selection of a DNA intercalating redox probe retaining a strong affinity binding to ds-DNA at the PCR measurement temperature of 72 °C (corresponding to the PCR elongation step). This has also been achieved through the identification of the key parameters governing the onset electrochemical signal decrease and amplitude signal decrease as a function of the PCR cycle for a given DNA intercalating redox probe, thus allowing us to predict the electrochemical PCR kinetic plots from the values of the DNA affinity binding constant determined as a function of temperature. To the best of our knowledge, the analytical performances of the current electrochemical qPCR outperform all of those previously published, in terms of detection limit, dynamic range, reproducibility and melting curve analysis compared to that achieved on a commercialized bench-top fluorescence-based qPCR instrument.