Voltammetric Determination of Underivatized Oligonucleotides on Graphite Electrodes Based on Their Oxidation Products

Abstract

A new electrochemical method to determine underivatized oligonucleotides is developed. The electro-oxidation of the adenine moieties of adsorbed oligonucleotides at elevated potentials on pyrolytic graphite electrodes (PGE) in neutral or alkaline media gives rise to electroactive products strongly adsorbed on the electrode surface. The extent of the redox processes of these products, with formal potential close to 0 V (vs Ag /AgCl) at pH 10, correlates well with the amount of parent oligonucleotide. Various electrochemical techniques have been compared and applied to the detection of specific DNA sequences and synthetic homopolynucleotides. Detection limits of 2 and 10 ng for (dA)20 and a 21-mer sequence of HIV-1, respectively, have been achieved using sample volumes of 10 microL. Moreover, the adsorbed oxidized oligonucleotide shows electrocatalytic activity toward the oxidation of NADH. The capability of the new method to detect DNA hybridization is discussed.

DNA-based biosensor for the electrocatalytic determination of antioxidant capacity in beverages

“…Accordingly, ssDNA leads to higher oxidation currents than dsDNA because of their flexibility and better accessibility of nucleobases to the electrode surface (de-los-Santos-Álvarez et al, 2002). Since polynucleotides strongly adsorb on carbon electrodes, the oxida-tion of a layer of dA21 was carried out after physical adsorption of the ssDNA on the electrode surface.…”

Electrochemical DNA-sensor for evaluation of total antioxidant capacity of flavours and flavoured waters using superoxide radical damage

“…Owing to the flexibility and better accessibility, nucleobases in a ssDNA are readily oxidised than in a dsDNA, leading to a higher oxidation current at an electrode surface (de-los-Santos-Álvarez et al, 2002). SWV was used to observe the electrochemical response of the oxidation of guanine and adenine immobilised on a GCE.…”

Electrocatalytic evaluation of DNA damage by superoxide radical for antioxidant capacity assessment

“…Given that both radical attacks led to different products, the reported primary OH Å radical promoter role of O ÅÀ 2 remains uncertain. The adsorbed species was shown to efficiently catalyze the oxidation of NADH reducing the overpotential by more than 300 mV at pyrolytic graphite electrodes [27,28,32]. This ability can be exploited, in principle, to detect the DNA damage.…”

“…1b) were virtually identical suggesting that the same compound is formed in both types of oxidation. According to previous studies on the electro-oxidation of adenine derivatives on carbon electrodes in phosphate buffer [28,32,33], the compound responsible for redox process at +0.041 V is a diimine species strongly adsorbed on the electrode surface. This compound was also identified after oxidation of guanine derivatives [25][26][27].…”