Comparison between the behaviour of native and denatured DNA at mercury and gold electrodes by capacity measurements and cyclic voltammetry

Direct Electrochemical Oxidation of DNA on Polycrystalline Gold Electrodes

“…The formation of adsorbed DNA monolayers at gold surfaces was confirmed by capacity measurements [23] and further supported by microgravimetric experiments with Au quartz crystal microbalance (QCM) [26,27] and X-ray photoelectron spectroscopy [28]. However, the electrochemical response of DNA adsorbed on Au was only observed in the region where the oxidation of the gold surface occurs, i.e., at 1.1.…”

“…No electrochemical signal corresponding to any DNA redox transformations was obtained with DNAmodified electrodes in the potential range from 0 to À 1.5 V upon CVand SWV scanning. This result most probably stems from the desorption of DNA from gold with increasing cathodic overvoltage, before the potential of any nucleotide reduction could be reached [23,26,27]. To avoid the effect of the DNA desorption from the negatively charged Au electrode surface further studies of electrochemical activity of DNA on gold were performed within the potential range from 0 to 1 V, where no formation of surface oxides occurs (see background curves Figs.…”

“…The kinetics of the DNA electrooxidation in this case was masked by the formation of gold surface oxides and possible poisoning of the electrode surface by the oxidation products [24]. At negative surface charges of the gold electrode, desorption of DNA occurs before the potentials for any nucleotide reduction could be scanned [23,26,27]. Thus, the available DNA electrochemical sensing technology at gold surfaces is limited either to the indirect detection by means of electrochemically active compounds, capable of binding with the adsorbed DNA layer, specifically, Co(bpy) 3 3 and similar complexes [29 ± 31], or to the detection of hybridization events with redox labeled complementary sequences [32] and with redox markers [33].…”

“…However, the electrochemical response of DNA adsorbed on Au was only observed in the region where the oxidation of the gold surface occurs, i.e., at 1.1. V, and it was related with the overall oxidation of DNA guanines/adenines exposed to the Au surface [23,24]. The results enabled us to estimate roughly the surface coverage with DNA, from the difference between the charges passed during the oxidation in the presence and in the absence of DNA [23,24], but did not clear up the possible mechanism of DNA oxidation on gold.…”

“…V, and it was related with the overall oxidation of DNA guanines/adenines exposed to the Au surface [23,24]. The results enabled us to estimate roughly the surface coverage with DNA, from the difference between the charges passed during the oxidation in the presence and in the absence of DNA [23,24], but did not clear up the possible mechanism of DNA oxidation on gold. The kinetics of the DNA electrooxidation in this case was masked by the formation of gold surface oxides and possible poisoning of the electrode surface by the oxidation products [24].…”