Electrochemical DNA-based Biosensor Research Articles

DNA Biosensor for Rapid Detection of Genotoxic Compounds in Soil Samples

An electrochemical DNA-based biosensor is proposed as a fast and easyscreening method for the detection of genotoxic compounds in soil samples. The biosensorwas assembled by immobilising double stranded Calf thymus DNA on screen-printedelectrodes. The interactions between DNA and environmental pollutants can causevariations of the electrochemical proprieties of DNA when they cause a DNA damage.Preliminary studies were performed using benzene, naphthalene and anthracene derivativesas model compounds. The effect of these compounds on the surface-confined DNA wasfound to be linearly related to their concentration in solution. On the other hand, theobjective was to optimise the ultrasonic extraction conditions of these compounds fromartificially spiked soil samples. Then, the applicability of such a biosensor was evaluated byanalysing soil samples from an Italian region with ecological risk (ACNA of Cengio, SV).DNA biosensor for qualitative analysis of soil presented a good correlation with a semiquantitativemethod for aromatic ring systems determination as fixed wavelengthfluorescence and interestingly, according results were found also with other bioassays.This kind of biosensors represent a new, easy and fast way of analysis of polluted sites, therefore they can be used as early warnings devices in areas with ecological risk as in situ measurement.

Kinetic study of the degradation of a potential local anesthetic drug in serum using the DNA-based electrochemical biosensor

DNA-drug association interaction at the DNA modified screen-printed electrode for 1-methyl-2-piperidinoethylester of 2-hexoxyphenylcarbamic acid was found leading to an accumulation of the drug within the DNA layer. A procedure for the determination of drug in blood serum matrix using the protein precipitation and voltammetric measurement of the electroactive drug with the DNA biosensor was obtained and an effort was done to apply it for an assay of the drug enzymatic degradation in human and rabbit sera at 37 °C.

Anti/pro-oxidative properties of selected standard chemicals and tea extracts investigated by DNA-based electrochemical biosensor

A DNA-modified screen-printed carbon electrode and the [Co(phen)3]3+ complex as an electrochemical DNA marker were used for the evaluation of anti/pro-oxidative properties of α-tocopherol, β-carotene, quercetin, kaempferol and myricetin, as well as various tea extracts. Reactive oxygen species were generated using a model cleavage mixture composed of 5×10−7 M [Cu(phen)2]2+ as the catalyst, 1×10−3 M ascorbic acid as the chemical reductant and air oxygen as the natural oxidant. The antioxidative activity of standard chemicals increases with their concentration, reaching a maximum where prooxidative behaviour becomes of importance. Antioxidative effects of tea exctracts varied with the temperature of their preparation. Similar results were obtained by the 2, 2’-diphenyl-1-picrylhydrazyl free radical method.

Engineering DNA-electrode connectivities: manipulation of linker length and structure

The development of electrical or electrochemical DNA-based biosensors requires the attachment of oligonucleotides to electrode surfaces through linkages with appropriate structural and electronic properties. Using a straightforward and versatile synthetic method, we prepared DNA molecules with a series of thiol-terminated linkers containing either ethane, hexane, or xylene spacers connected either to a terminal deoxyribose C5′ or thymine C5. The modified oligonucleotides self-assemble on gold electrodes and form densely-packed monolayers. The kinetics and extent of monolayer formation are sensitive to the rigidity of the tether, with the xylene-based linker slowing adsorption to the gold surface relative to the more flexible hexane-based linker. The monolayer formation is also less efficient for double-stranded versus single-stranded DNA. The redox-active intercalator methylene blue (MB) was used to study charge transport through the series of different DNA films. The heterogeneous electron-transfer kinetics are modulated by the structure of the DNA-electrode connection, with a linker attached directly to the 5-CH 3 of thymine facilitating the most efficient charge transport through the film. These studies constitute the first systematic analysis of the effect of linker structure on DNA-electrode coupling, and provide important information for the development of new electrical DNA biosensors.

Evaluation of the redox properties and anti/pro-oxidant effects of selected flavonoids by means of a DNA-based electrochemical biosensor.

Quercetin and rutin as well as catechin and epigallocatechin gallate were investigated, as widely distributed representatives of flavonols and flavanols, respectively, regarding their anti/pro-oxidant properties. The flavonoids are irreversibly oxidized at a dsDNA-modified screen-printed electrode within 0.368 to 0.449 V vs. SHE without binding to DNA. Using the DNA biosensor the detection scheme of a DNA prevention/degradation exploits the [Co(phen)(3)](3+) complex as an electrochemical DNA marker. Antioxidant activity of flavonoids was tested in a model cleavage mixture composed of 5 x 10(-7) mol L(-1) [Cu(phen)(2)](2+) as the catalyst, 1 x 10(-3) mol L(-1) ascorbic acid as the chemical reductant and atmospheric oxygen as the natural oxidant where reactive oxygen radicals are generated. The antioxidant activity increases with the concentration of flavonoids reaching a maximum where pro-oxidative behaviour becomes of importance. The pro-oxidant potency of flavonoids depends on the presence of atmospheric oxygen and follows the order quercetin>rutin>epigallocatechin gallate>catechin.

Toward the DNA electronics

DNA is one of the most promising molecules as the scaffold for molecular nanotechnology and nanoelectronics. For realizing the molecular devices constructed with DNA, three kinds of function is required such as (1) circuit and control of the conductivity, (2) switching and (3) storage. We have found that the electrical conducting properties of the DNA networks are strongly depended on the doping condition. Photo-switching (current enhancement with shining the light) and magnetoresistance effect are observed in the dye-modified DNA and Co ions doped DNA, respectively. Furthermore, DNA network pattern can be patterned on the Si/SiO 2 surface. These results have significant implications for the application of DNA in electronic devices and in DNA-based electrochemical biosensors.

DNA electrochemical biosensors.

Disposable electrochemical DNA-based biosensors are reviewed; they have been used for the determination of low-molecular weight compounds with affinity for nucleic acids and for the detection of the hybridisation reaction. The first application is related to the molecular interaction between surface-linked DNA and the target pollutants or drugs, in order to develop a simple device for rapid screening of toxic or similar compounds. The determination of such compounds was measured by their effect on the oxidation signal of the guanine peak of calf thymus DNA immobilised on the electrode surface and investigated by chronopotentiometric analysis. The DNA biosensor is able to detect known intercalating compounds, such as daunomycin, polychlorinated biphenyls (PCBs), aflatoxin B1, and aromatic amines. Applicability to river and waste water samples is also demonstrated. Disposable electrochemical sensors for the detection of a specific sequence of DNA were realised by immobilising synthetic single-stranded oligonucleotides onto a graphite screen-printed electrode. The probes became hybridised with different concentrations of complementary sequences present in the sample. The hybrids formed on the electrode surface were evaluated by chronopotentiometric analysis using daunomycin as indicator of the hybridisation reaction. The hybridisation was also performed using real samples. Application to apolipoprotein E (ApoE) is described, in this case samples have to be amplified by PCR and then analysed by DNA biosensor. The extension of such procedures to samples of environmental interest or to contamination of food is discussed.

Affinity electrochemical biosensors for pollution control

Abstract Disposable, electrochemical DNA-based biosensors have been exploited for the determination of low-molecular-weight compounds with affinity for nucleic acids. The application is related to the molecular interaction between the surface-linked DNA obtained from calf thymus and the target pollutants or drugs, in order to develop a simple device for rapid screening of genotoxic or similar compounds. The determination of such compounds was measured by their effect on the oxidation signal of the guanine peak of the DNA immobilized on the electrode surface and investigated by chronopotentiometric or square-wave voltammetric analysis. The DNA biosensor is able to detect known intercalating and groove-binding compounds such as daunomycin, polychlorinated biphenyls (PCBs), aflatoxin B1, and aromatic amines. Applicability to river and waste water samples is discussed and reported.