Detection of the damage caused to DNA by a thiophene-S-oxide using an electrochemical DNA-biosensor

Quantification of DNA by a Thermal-Durable Biosensor Modified with Conductive Poly(3,4-ethylenedioxythiophene)

The general clinical procedure for viral DNA detection or gene mutation diagnosis following polymerase chain reaction (PCR) often involves gel electrophoresis and DNA sequencing, which is usually time-consuming. In this study, we have proposed a facile strategy to construct a DNA biosensor, in which the platinum electrode was modified with a dual-film of electrochemically synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) resulting in immobilized gold nanoparticles, with the gold nanoparticles easily immobilized in a uniform distribution. The DNA probe labeled with a SH group was then assembled to the fabricated electrode and employed to capture the target DNA based on the complementary sequence. The hybridization efficiency was evaluated with differential pulse voltammetry (DPV) in the presence of daunorubicin hydrochloride. Our results demonstrated that the peak current in DPV exhibited a linear correlation the concentration of target DNA that was complementary to the probe DNA. Moreover, the electrode could be reused by heating denaturation and re-hybridization, which only brought slight signal decay. In addition, the addition of the oxidized form of nicotinamide adenine dinucleotide (NAD⁺) could dramatically enhance the sensitivity by more than 5.45-fold, and the limit-of-detection reached about 100 pM.

Detection of DNA Damage Induced by Hydroquinone and Catechol Using an Electrochemical DNA Biosensor

DNA damage induced by hydroquinone and catechol was detected by an electrochemical method. Calf thymus DNA was immobilized onto the surface of a pretreated glassy carbon electrode (GCE(ox)) to form a DNA/GCE(ox) modified electrode. Then the DNA/GCE(ox) was incubated in acetate buffer solution containing hydroquinone or catechol at a constant potential for the desired time. Differential pulse voltammetric experiments were then performed. The anodic peaks corresponding to the oxidation of guanisine and adenosine on the electrode could be observed on voltammetric curves. The experimental results showed that DNA damage could be detected using electrochemical DNA biosensors. The extent of DNA damage could be electrochemically recognized via the change of the anodic peak current. DNA damage induced by hydroquinone was greater than that by catechol. The response conditions were optimized with respect to DNA concentration, pH, ionic strength, and other variables.

The Application of DNA-Biosensors and Differential Scanning Calorimetry to the Study of the DNA-Binding Agent Berenil

The in situ DNA-damaging capacity of berenil (1) has been investigated usingan electrochemical approach employing double stranded (ds) DNA-modified glassy carbonelectrode biosensors. Electrochemical voltammetric sensing of damage caused by 1 todsDNA was monitored by the appearance of peaks diagnostic of the oxidation of guanineand adenine. When 1 was incorporated directly onto the biosensor surface, DNA damagecould be observed at concentrations of additive as low as 10 μM. In contrast, when thedsDNA-modified biosensor was exposed to 1, in acetate buffer solution, the method wasmuch less sensitive and DNA damage could be detected only in the presence of 100 μMberenil. When mixed solutions of 1 and single stranded (ss) DNA, polyguanylic acid orpolyadenylic acid were submitted to voltammetric study, the oxidation signals of therespective bases decreased in a concentration-dependent manner and the major variation ofthe adenine current peak indicated preferential binding of 1 to adenine. The electrochemical results were in close agreement with those deriving from a differentialscanning calorimetric study of the DNA-berenil complex.

Electrochemical Determination of Trace Promethazine Hydrochloride by a Pretreated Glassy Carbon Electrode Modified with DNA

A highly sensitive electrochemical biosensor for the detection of trace amounts of promethazine has been designed. Double stranded (ds)DNA molecules are immobilized onto a pretreated glassy carbon electrode (GCE(ox)) surface. The voltammetric behaviors of promethazine on DNA-modified electrode were explored by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The promethazine gave rise to a pair of well-defined peaks, which appeared at E(pc) = 52 mV and E(pa) = 96 mV (vs. Ag/AgCl) in 0.10 M acetate buffer (pH 5.0). The peak current was linearly enhanced with increasing the concentration of promethazine. The calibration was linear for promethazine over the range of 4.7 x 10(-10) to 9.3 x 10(-9) M with a correlation coefficient of 0.999. The limit of detection (LODs) was 3.0 x 10(-10) M (S/N = 3). The modified electrode was applied to determine promethazine in human blood samples with satisfactory results.

Electrochemistry of nanoscale DNA surface films on carbon

A DNA electrochemical biosensor is an integrated receptor-transducer device. The most important step in the development and manufacture of a sensitive DNA-biosensor for the detection of DNA-drug interactions is the immobilization procedure of the nucleic acid probe on the transducer surface. Magnetic A/C Mode atomic force microscopy (MAC Mode AFM) images in air were used to characterize two different procedures for immobilising nanoscale double-stranded DNA (dsDNA) surface films on carbon electrodes. Thin film dsDNA layers presented holes in the dsDNA film that left parts of the electrode surface uncovered while thicker films showed a uniform and complete coverage of the electrode. These two procedures for preparing dsDNA-biosensors were used to study the influence of reactive oxygen species (ROS) in the mechanism of DNA damage by quercetin, a flavonoid, and adriamycin, an anthracycline anticancer drug. The study of quercetin-DNA interactions in the presence of Cu(II) ions indicated that the formation of a quercetin-Cu(II) complex leads to the formation of ROS necessary to react with DNA, disrupting the helix and causing the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo). Reduced adriamycin radicals are able to directly cause oxidative damage to DNA, generating 8-oxodGuo and ROS are not directly involved in this genomic mutagenic lesion.

Investigation of double stranded DNA damage induced by quercetin-copper(II) using piezoelectric quartz crystal impedance technique and potentiometric stripping analysis

DNA damage by quercetin-Cu(2+) was monitored in real time by piezoelectric quartz crystal impedance (PQCI) technique. In the PQCI analysis, the frequency change was caused mainly by the changes in density-viscosity of DNA solution in the damage course. The influences of DNA, Cu(2+), and quercetin concentrations on the motional resistance change (DeltaR(m)) were investigated in detail. The results showed that quercetin exhibited pro-oxidative damage at lower concentrations while anti-oxidative protection at higher concentrations, and DeltaR(m) exhibited a linear relationship in the DNA concentration range from 200 to 1600 microg/ml. Potentiometric stripping analysis (PSA) was also used to observe the electrochemical behavior of damaged DNA. From PSA, a new peak at 0.84 V and a higher peak at 1.06 V were discovered, which suggested that more purines were exposed to the electrode surface during the damage course. In agarose-gel electrophoresis, catalase and biquinoline were found to effectively inhibit DNA damage, therefore, a possible damage mechanism was proposed.