A review of current strategies aimed at detecting nucleic acids (NA) using NA-modified solid electrodes reveals the versatility and potential of electrochemical detection in this field. What emerged at the beginning of 90s as a very promising detection system in DNA technology is now resulting in the first commercial devices. Many aspects of the experimental design, for example surface immobilisation and detection schemes, are outlined and evaluated. Although most approaches use hybridisation as the recognition reaction, those not based on hybridisation are also included. As is finally shown, great advances have been achieved, although further developments are required if electrochemical devices are to be suitable for routine measurement.
An electrochemical genosensor for the detection of nucleic acid sequences specific of Legionella pneumophila is reported. An immobilized thiolated hairpin probe is combined with a sandwich-type hybridization assay, using biotin as a tracer in the signaling probe, and streptavidin-alkaline phosphatase as reporter molecule. The activity of the immobilized enzyme was voltammetrically determined by measuring the amount of 1-naphthol generated after 2 min of enzymatic dephosphorylation of 1-naphthyl phosphate. The sensor allows discrimination between L. pneumophila and L. longbeachae with high sensitivity under identical assay conditions (no changes in stringency). A limit of detection of 340 pM L. pneumophila DNA, and a linear relationship between the analytical signal and the logarithm of the target concentration to 2 muM were obtained. Experimental results show the superior sensitivity and selectivity of the hairpin-based assay when compared with analogous sandwich-type assays using linear capture probes.
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.
The generation of a new electrocatalytic system for NADH after oxidizing flavin adenine dinucleotide (FAD) is shown. The oxidation is performed in alkaline medium until +1.4 V (Ag/AgCl) at graphite electrodes. The catalytic activity is ascribed to the electrooxidized moiety of FAD and not to quinone surface groups. A comparison between this catalyst and that attributed to poly(FAD) (Karyakin, A. A.; Ivanova Y. N.; Revunova, K. V.; Karyakina, E. E. Anal. Chem. 2004, 76, 2004-2009.) is presented. It is concluded that the surface quinone groups generated during the strong anodization of the electrode in acidic medium at 2-2.5 V and not the poly(FAD) are responsible for the catalytic activity described in the above mentioned work.
The knowledge of the redox chemistry of nucleic acids (NA) is of paramount importance in cancer and aging research. Charge migration through DNA is also involved in biologically relevant functions such as DNA damage and repair. In the first part of this article the main aspects of the electrochemistry of nucleic acids at solid electrodes are revised, including redox processes, photoelectroactivity and electrical conductivity. In the second part, an overview of its applications is presented. Methods for electrochemical detection of NA, NA-based biosensors for detection of nonnucleic acid molecules, studies on the nature and dynamics of interactions and structural conformations of NA, are some applications that take advantage of NA electrochemistry at solid electrodes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.