Complex electrochemical and impedimetric evaluation of DNA damage by using DNA biosensor based on a carbon screen-printed electrode

DNA biosensor (DNA/SWCNT-COOH-CHIT/SPCE) composed of dsDNA adsorptive layer on a carboxylated single-walled carbon nanotubes-chitosan composite deposited at a commercial carbon based screen-printed electrode has been prepared and applied to a complex investigation of damage to DNA by the Fenton type cleavage agent (hydroxyl radicals formed in the mixture of Cu2+, H 2O2 and ascorbic acid) and copper(ii)-quercetin system in 0.1 M PBS pH 7.0 under aerobic conditions. The dsDNA damage detection is performed by using square-wave voltammetry (SWV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 × 10-7 M thioridazine and 1 × 10-3 M K4[Fe(CN) 6]/K3Fe(CN)6 in the 0.1 M phosphate buffer solution, pH 7.0. Initial enhancement of the intrinsic guanine and adenine moieties SWV response over that of original dsDNA one indicates opening of the helix structure in the first stage of damage. At the same time, decrease in the intercalated thioridazine response confirms damage of the helix structure in parallel to deep degradation of the DNA chain and its removal from the electrode surface as indicated by the CV and EIS measurements in the presence of the [Fe(CN)6]3-/4- redox indicator in solution. © 2011 The Royal Society of Chemistry

Biosensor with Protective Membrane for the Detection of DNA Damage and Antioxidant Properties of Fruit Juices

With the purpose to prepare a DNA biosensor protected with an outer-sphere membrane against high molecular weight interferences, a carbon film electrode was layer-by-layer modified with dsDNA and chitosan. Using cyclic and square-wave voltammetry and impedance spectroscopy, the oxidative damage of DNA by the hydroxyl and superoxide anion radicals was detected which consists of opening of the helix structure followed by deep DNA chain degradation. The biosensor has been applied to the detection of the antioxidant effect of apple and orange juices. The investigation of the novel biosensor with a protective membrane represents a significant contribution to the field of DNA biosensors utilization. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Impedimetric nanostructured disposable DNA-based biosensors for the detection of deep DNA damage and effect of antioxidants

Novel impedimetric nanostructured disposable DNA-biosensors have been created using a layer of multiwalled carbon nanotubes (MWNT) and double stranded calf thymus or herring sperm DNA deposited on the surface of a screen-printed carbon electrode (SPCE) by layer-by-layer and mixed coverage. The presence of DNA significantly decreases the electroconductivity of the MWNT/SPCE interface and represents a charge barrier for the transport of the [Fe(CN6)]3- redox probe ions. Hence, electrochemical impedimetric procedure performed with DNA/MWNT/SPCE sensor in 0.1 M phosphate buffer solution (PBS) pH 7.0 using 1 mM [Fe(CN6)]3- was developed for the evaluation of deep DNA damage caused by reactive oxygen species formed in situ as well as antioxidative effects of rutin and tea extracts. Good correlation has been found between the charge transfer resistance change obtained as a parameter of the impedimetric equivalent circuit and the voltammetric current response change of the [Fe(CN6)]3- / [Fe(CN6)]4- redox couple measured at the DNA modified and bare SPCEs. © 2008 by ESG

Disposable electrochemical biosensor with multiwalled carbon nanotubes - Chitosan composite layer for the detection of deep DNA damage

A novel electrochemical DNA-based biosensor for the detection of deep DNA damage was designed employing the bionanocomposite layer of multiwalled carbon nanotubes (MWNT) in chitosan (CHIT) deposited on a screen printed carbon electrode (SPCE). The biocomponent represented by double-stranded (ds) herring sperm DNA was immobilized on this composite using layer-by-layer coverage to form a robust film. Individual and complex electrode modifiers are characterized by a differential pulse voltammetry (DPV) with the DNA redox marker [Co(phen)3]3+, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with [Fe(CN)6]3- as a redox probe in a phosphate buffer solution (PBS). A good correlation between the CV and EIS parameters has been found, thus confirming a strong effect of MWNT on the enhancement of the electroconductivity of the electrode surface and that of CHIT on the MWNT distribution at the electrode surface. Differences between the CV and EIS signals of the electrodes without and with DNA are used to detect deep damage to DNA, advantageously using simple working procedures in the same experiment. 2008 © The Japan Society for Analytical Chemistry

The influence of nonionic surfactants and B-cyclodextrin on the state of 5-phenylthio-8-mercaptoquinoline in aqueous media

© Research India Publications 2015. Using spectrophotometry method the condition of 5-phenylthio-8-mercaptoquinoline within a wide pH range (pH 0-10) was studied in water, the aqueous solutions of a nonionic surfactant Brij35 and β-cyclodextrin (βCD). It was found that in water within the range of pH = 2-6 5-phenylthio-8-mercaptoquinoline is poorly soluble after the self-association of zwitterionic (HR ±) reagent forms. In other areas of pH the aqueous solutions of the reagent are transparent due to the transition of zwitterions in protonated (H2R+) or anionic (R-) form. The spectral parameters of mercaptoquinoline in surfactant solutions or cyclodextrin were similar to the observed ones in aqueous, strongly acidic and alkaline environments. However, in neutral and slightly acidic pH areas the spectra of the reagent differed greatly in the presence of βCD and Brij35. The latter allowed to suggest that due to the different polarity of the mercaptoquinoline microenvironment in surfactant solutions and βCD various tautomeric forms of the reagent are stabilized. The molecular form (HR) is realized in the micellar environment, and the presence of cyclodextrin stabilizes the zwitterionic form (± HR), which proves the presence of a chromophore node in an aqueous medium. By varying the ratio of Brij35 and βCD in the neutral pH range, it is possible to observe the corresponding tautomeric transition. The comparison of 5-phenylthio-8-mercaptoquinoline absorption spectra results in various environments allowed to identify the spectral parameters and pH range of different reagent forms. The mathematical processing of optical density absorbance dependencies on pH showed that Brij35 supplements, unlike βCD ones, change the acid-base properties of a reagent by micelle solubilization. The influence of cyclodextrin is explained by the formation of "guest-host" complex with the phenyl substitute of 5-phenyltio-8-mercaptoquinoline. As micelle forming surfactants so as cyclodextrins may be used to increase the solubility of 8-mercaptoquinoline aromatic derivatives in water

Probiotics for plants: NO-producing lactobacilli protect plants from drought

After the inoculation of wheat roots with a suspension of the bacterium Lactobacillus plantarum, reduction or decrease of oxidative stress detected by the accumulation of H2O2 and MDA was found in leaves. Activation of catalase and increased integral antioxidant capacity in seedlings treated with NO-producing lactobacilli were detected during the determination of the contribution of bacterial NO to the plant stress reaction. Thus, for the first time, we have demonstrated that lactobacilli affect plant adaptive responses to stress by the involvement of nitric oxide. © 2014 Pleiades Publishing, Inc

An NMR relaxivity and ESR study of the interaction of the paramagnetic manganese(II) and gadolinium(III) ions with anionic, cationic and neutral water-soluble polymers and their mixtures

© 2017 Elsevier B.V.Solutions of the series of polymers (sodium polystyrene sulfonate, polyethyleneimine, and poly-N-vinylpyrrolidone) and certain mixtures thereof were studied by NMR relaxation and ESR spectroscopy using manganese(II) and gadolinium(III) ions as paramagnetic probes. The growth of the NMR-relaxation efficiency (relaxivity, R1,2) is observed in solutions of the anionic polymer, as well as the decrease of R1,2 - in the case of the cationic polymer. For mixtures of polymers, the dependent on the solution composition non-monotonic changes of R1,2 are caused either by a formation of metal-interpolymer complexes or by a competitive cation/polymer substitution. For both ions, the changes in the ESR spectra of their polyelectrolyte solutions were analyzed. In case of sodium polystyrene sulfonate and blends thereof, the ESR spectra parameters are only slightly broadened compared to the pure metal aqua ion's, whereas for the polyethyleneimine solution the ESR spectra lines broaden greatly at pH > 7 up to their disappearance. All these effects were explained by the distinction of ion probes’ binding mode to polyelectrolytes of different nature. Addition of NaCl to manganese(II) solutions containing polystyrene sulfonate, or mixtures thereof with PVP or PEI, lead to recovery of R1,2 values, close to the probes’ aqua ions relaxivities due to the release of the latter from the polymer/medium interface into the bulk water, while no changes were detected for PEI solutions

What Electrophysiology Tells Us About Alzheimer’s Disease::A Window into the Synchronization and Connectivity of Brain Neurons

Electrophysiology provides a real-time readout of neural functions and network capability in different brain states, on temporal (fractions of milliseconds) and spatial (micro, meso, and macro) scales unmet by other methodologies. However, current international guidelines do not endorse the use of electroencephalographic (EEG)/magnetoencephalographic (MEG) biomarkers in clinical trials performed in patients with Alzheimer’s disease (AD), despite a surge in recent validated evidence. This Position Paper of the ISTAART Electrophysiology Professional Interest Area endorses consolidated and translational electrophysiological techniques applied to both experimental animal models of AD and patients, to probe the effects of AD neuropathology (i.e., brain amyloidosis, tauopathy, and neurodegeneration) on neurophysiological mechanisms underpinning neural excitation/inhibition and neurotransmission as well as brain network dynamics, synchronization, and functional connectivity reflecting thalamocortical and cortico-cortical residual capacity. Converging evidence shows relationships between abnormalities in EEG/MEG markers and cognitive deficits in groups of AD patients at different disease stages. The supporting evidence for the application of electrophysiology in AD clinical research as well as drug discovery pathways warrants an international initiative to include the use of EEG/MEG biomarkers in the main multicentric projects planned in AD patients, to produce conclusive findings challenging the present regulatory requirements and guidelines for AD studies

Biosensor with Protective Membrane for the Detection of DNA Damage and Antioxidant Properties of Fruit Juices

With the purpose to prepare a DNA biosensor protected with an outer-sphere membrane against high molecular weight interferences, a carbon film electrode was layer-by-layer modified with dsDNA and chitosan. Using cyclic and square-wave voltammetry and impedance spectroscopy, the oxidative damage of DNA by the hydroxyl and superoxide anion radicals was detected which consists of opening of the helix structure followed by deep DNA chain degradation. The biosensor has been applied to the detection of the antioxidant effect of apple and orange juices. The investigation of the novel biosensor with a protective membrane represents a significant contribution to the field of DNA biosensors utilization. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim