Towards deeper understanding of DNA electrochemical oxidation on carbon electrodes

• Published in: Electrochemistry communications 2021-03, Vol.124, p.106947, Article 106947
• Main Authors: Suprun, Elena V., Kutdusova, Gulnaz R., Khmeleva, Svetlana A., Radko, Sergey P.
• Format: Article
• Language: English
• Subjects: Carbon electrode; Double helix; Nucleic acid; Oligonucleotide; Oxidation
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2021.106947

[Display omitted] •The formation of DNA double helix blocks the oxidation of G and A residues on electrode.•The oxidation signals for G and A of ssDNA are exponentially decrease with molecular weight.•Large molecular weight dsDNA of natural origin does not give oxidation signals from G and A.•Native DNA oxidizes due to G and A of low molecular weight single-stranded fragments. To better understand the electrochemical behavior of deoxyribonucleic acid (DNA) on carbon electrodes, the oxidation of synthetic oligonucleotides of 4 to 72 nucleotides long, their thermally stable duplexes, polymerase chain reaction amplicons of 141 base pairs long, and samples of double- and single-stranded DNA (dsDNA and ssDNA) of natural origin was studied on carbon screen printed electrodes by square wave and cycling voltammetry within the potential range of 0.5–1.5 V (vs. Ag/AgCl). In square wave voltammograms, ssDNA of natural origin produced two distinct signals at approximately 0.75 V and 1.05 V (at the nucleotide concentration of 1 mM; phosphate buffer, pH 7.4), attributed to the oxidation of guanine (Gua) and adenine (Ade) residues, respectively. The oxidation reactions of both residues of ssDNA were found diffusion-controlled. Similar to that, synthetic DNA oligonucleotides exhibited the oxidation peaks at potentials of either around 0.85 V or 1.15 V (at the nucleotide concentration of 1 mM), or both, depending on their sequence. In contrast to ssDNA, dsDNA molecules showed no sign of oxidation on carbon electrodes. The low molecular weight ssDNA fragments were found as the main contributors to the overall electrooxidation currents generated via oxidation of Gua and Ade residues of DNA from a natural source. Oxidation signals of Gua and Ade residues exponentially decreased with the oligonucleotide length. In the thermally stable duplex DNA molecules even as short as those of 24 base pairs long, Gua and Ade restudies were shown to be inaccessible for oxidation on carbon electrodes.