Adsorptive Transfer Stripping Voltammetry Research Articles

A Reduced Graphene Oxide‐based Electrochemical DNA Biosensor for the Detection of Interaction between Cisplatin and DNA based on Guanine and Adenine Oxidation Signals

AbstractA glassy carbon electrode (GCE) was modified by electrochemically reduced graphene oxide (ERGO) for subsequent dsDNA immobilization. The interaction of cisplatin with dsDNA was studied at this modified electrode. Quantitative investigations were performed by adsorptive transfer stripping voltammetry (AdTSV) using differential pulse voltammetry (DPV). The morphology and structure of graphene oxide (GO) and ERGO modified GCEs (GO/GCE and ERGO/GCE, respectively) were characterized by UV‐vis, FT‐IR, Raman spectroscopy and cyclic voltammetry. Compared with the bare GCE and the GO/GCE, the ERGO/GCE exhibited excellent electrocatalytic activity towards the oxidation of dsDNA due to guanine and adenine groups, testified by high oxidation peak currents and decreased oxidation potentials. The interaction of micromolar concentrations of cisplatin with surface confined dsDNA was readily detected as inferred from the decrease of the voltammetric oxidation peaks of guanine and adenine. This trend was significantly greater at the ERGO/GCE compared to the GO/GCE. The interaction of cisplatin with dsDNA was also studied in solution phase by AdTSV with detection at the ERGO/GCE.

Electrochemical study of dsDNA on carbon nanotubes paste electrodes applying cyclic and differential pulse voltammetry

Abstract Abstract Carbon nanotubes paste electrodes (CNTPEs) in combination with adsorptive transfer stripping voltammetry are shown to be very suitable for the determination of calf thymus double-stranded DNA (dsDNA). The performance of three types of multi-walled carbon nanotubes paste electrodes (MWCNTPEs) is investigated. The effects of surface pre-treatment and accumulation conditions on the adsorption and electrooxidation of the dsDNA at MWCNTPEs are also described. The results indicate that the electroactivity inherent to carbon nanotubes/paste electrodes allows a large enhancement of the guanine oxidation signal compared to that obtained at the conventional carbon paste electrodes (CPEs). Moreover, the extent of the enhancement dependents on the type of MWCNTs incorporated into the paste. Based on the signal of guanine, under optimal conditions, very low levels of dsDNA can be detected following short accumulation times for all three types of MWCNTPEs (MWCNTPE1, MWCNTPE2, MWCNTPE3), with detection limits of 2.64 mg L−1, 2.02 mg L−1 and 1.46 mg L−1, respectively. Additionally, the dsDNA isolated from rat liver tissues is determined by use of the previously mentioned MWCNTPEs. Graphical abstract

Synthesis, characterization, DNA binding properties and antioxidant activity of a manganese(II) complex with NO6 chromophore

The mononuclear complex [Mn(thiophenyl-2-carboxylate)2(H3tea)] (1), where H3tea=triethanolamine has been synthesized, characterized, while the DNA binding properties and the antioxidant activity were studied. The crystal structure of 1 is also reported. The interaction between 1 and calf thymus double stranded (ds) DNA was electrochemically at a calf thymus DNA (CT-DNA) modified carbon paste electrode (CPE) and spectrophotometrically investigated, respectively. Adsorptive transfer stripping voltammetry showed that the interaction mode between 1 and CT-DNA depends on manganese(II) complex concentration. UV studies between 1 and CT-DNA revealed that 1 can bind to CT-DNA by the intercalative binding mode and the binding constant has been calculated. A competitive study with acridine orange (AO) showed that 1 exhibits the ability to displace the DNA-bound AO, since 1 binds to the DNA in competition with AO. In vitro antioxidant activity of free ligands and 1 was evaluated using five different antioxidant assays: a) interaction with 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, b) the ΗΟ mediated oxidation of DMSO, c) scavenging of superoxide anion radicals, d) inhibition of lipid peroxidation and e) soybean lipoxygenase (LOX) inhibition. The results revealed the selectivity of the manganese complex to different free radicals as a consequence of its physicochemical feature. In particular, 1 presents significant inhibitory activity on LOX, with IC50=30μM and selectivity to the inhibition of superoxide anion radicals and thus a promising candidate as a superoxide dismutase (SOD) biomimetic.

A study of the antioxidative behavior of phenolic acids, in aqueous herb extracts, using a dsDNA biosensor

Abstract Electrochemical DNA biosensors are promising tools for the fast, inexpensive and simple in vitro analysis for the determination of free radicals and antioxidants. High concentrations of antioxidants in such compounds as phenolic acids and plant extracts, act as free radical terminators which reduce the effect of the oxidative dam-age on DNA. The electrochemical behavior of three representative phenolic acids, caffeic acid, gallic acid and trolox were studied by cyclic voltammetry. Moreover, the determination of the above antioxidants under the optimized conditions (scan rate, deposition potential and time) using differential pulse voltammetry was also investigated. In vitro studies focused on their antioxidative effect were performed by adsorptive transfer stripping voltammetry and dsDNA biosensor. Using Fenton’s system, with FeSO4 and H2O2 was chosen as a strong oxidative system. This biosensor was applied as a screening antioxidant test in order to estimate the antioxidant capacity of aqueous herb extracts.

Determination of 7,12-Dimethylbenz[a]Anthracene in Orally Treated Rats by High-Performance Liquid Chromatography and Transfer Stripping Voltammetry

A number of polycyclic aromatic hydrocarbons (PAHs) have been shown to be toxicants, and induce carcinogenic and immunotoxic effects. As a model PAH agent, 7,12-dimethylbenz[a]anthracene (DMBA) was the strongest one tested in terms of its biological activities and biotransformation. A new and simple high-performance liquid chromatographic (HPLC) method with diode-array detection at 290 nm was developed and validated for monitoring of DMBA in different matrices (serum, liver and kidney) of rats orally treated with DMBA. Furthermore, the applicability of adsorptive transfer stripping voltammetry (AdTSV) on the pencil-lead graphite electrode to these samples was illustrated using our previously reported data for bulk aqueous solutions of DMBA. HPLC and AdTSV methods, which were compatible with each other, allowed DMBA to be detected down to the levels of 3.82x10-9 M (0.98 ppb) and 6.73x10-9 M (1.73 ppb), respectively. Olive oil solutions of DMBA in dose 50 mg/kg were orally administered. 60 days after a single dose of DMBA, its concentrations in these biological samples from rats were measured by means of both methods. Because of rapid biotransformation, DMBA could not be detected in serum. Only low levels of the compounds were deposited unchanged in kidney whereas its levels were considerably higher in liver. These methods were also applied to the assay whether there is an influence of the intake of aqueous extracts of Hypericum Perforatum L. plant on the parent DMBA levels accumulated in rat tissues.

Voltammetric behavior of benzo[a]pyrene at boron-doped diamond electrode: A study of its determination by adsorptive transfer stripping voltammetry based on the enhancement effect of anionic surfactant, sodium dodecylsulfate

Benzo[a]pyrene (BaP), a member of the polycyclic aromatic hydrocarbon (PAH) class, is one of the most potent PAH carcinogens. The electrochemical oxidation of BaP was first studied by cyclic voltammetry at the boron-doped diamond electrode in non-aqueous solvent (dimethylsulphoxide with lithium perchlorate). The compound was irreversibly oxidized in a single step at high positive potential, resulting in the well-resolved formation of a couple with a reduction and re-oxidation wave at much lower potentials. Special attention was given to the use of adsorptive stripping voltammetry together with a medium exchange procedure in aqueous and aqueous/surfactant solutions over the pH range of 2.0–8.0. The technique in aqueous solutions had little value in practice because of too small oxidation peak current. This problem was solved when surfactants were added into the sample solution, by which the oxidation peak currents of BaP were found enhanced dramatically. The employed surfactants were sodium dodecylsulfate (anionic, SDS), cetyltrimethylammonium bromide (cationic, CTAB) and Tween 80 (non-ionic). Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in Britton–Robinson buffer, pH 2.0 containing 2.5×10−4M SDS at +1.07V (vs. Ag/AgCl) (after 120s accumulation at +0.10V). The process could be used to determine BaP in the concentration range of 16–200nM (4.04–50.46ngmL−1), with a detection limit of 2.86nM (0.72ngmL−1). This method was also applied to determine BaP in model water sample prepared by adding its different concentrations into tap water.

Adsorption of cetyltrimethylammonium bromide and cetyldimethylbenzylammonium chloride on a hanging mercury electrode studied by adsorptive transfer stripping voltammetry

The adsorption of cetyltrimethylammonium bromide (CTAB) and cetyldimethylbenzylammonium chloride (CDBACl) on a hanging mercury electrode is studied using adsorptive transfer stripping voltammetry. The surfactants are adsorbed on mercury and are then transferred in KBr or KCl under various conditions, including temperatures from 1 to 40°C, open or closed circuits with different initial potentials, and repeated scans, etc. The results are compared with previously published results on the adsorption of CTAB or CDBACl on mercury, where condensed films were formed and are quite different than those obtained by adsorptive stripping voltammetry. In this case, an absence of condensed film is observed for CTAB. A condensed film with low capacitance value is formed in the case of CDBACl after transfer at low temperatures, or after repeated scans, resulting in reorientation of the molecules to more compact states. Capacity time curves at the potentials where the film is formed show in a few cases a nucleation and growth mechanism, with induction time and studied by the Avrami formulation, while an observed increase of the capacitance with time is attributed to the formation of hemimicelles. The results also indicate the importance of interactions between the hydrophobic chains.

Use of Adsorptive Transfer Stripping Voltammetry for Analyzing Variations of Cytosine Methylation in DNA

AbstractThe electrochemical behavior and thermal stability of double stranded oligonucleotides containing 5‐methyl‐cytosine and 7‐deaza‐guanosine as nucleotide analogues, as well as of Jurkat genomic DNAs methylated to different degree were studied by ACV and SWV and by thernal denaturation analysis. ACV and SWV combined with thermal denaturation analysis of the natural and modified oligonucleotides gave information regarding the presence of methylation and the concomitant conformational changes. ACV and SWV of Jurkat DNA mixtures methylated to different degrees revealed a decrease of the peak heights with increasing methylation, indicating an increase of structural rigidity, in agreement with the thermal denaturation data. These results verify the, possibly local, conformational changes introduced by DNA methylation. The results obtained in all cases were reproducible.

Analytical Applications of Solid and Paste Amalgam Electrodes

The review describes working and reference electrodes based on solid and/or paste amalgams and their application for voltammetric, amperometric, and potentiometric determination of both inorganic and organic analytes. Attention is paid to their preparation, pre-treatment and possible modification, and their application in classical voltammetric arrangements, in flowing systems (HPLC-ED, FIA-ED), and in adsorptive transfer stripping voltammetry. The review confirms that amalgam electrodes can successfully substitute mercury electrodes and, in some special cases, offer possibilities not available to mercury electrodes.

Osmium Tetroxide, 2,2′-Bipyridine: Electroactive Marker for Probing Accessibility of Tryptophan Residues in Proteins

A complex of osmium tetroxide with 2,2'-bipyridine (Os,bipy) has been applied as a chemical probe of DNA structure as well as an electroactive DNA label. The Os,bipy has been known to form covalent adducts with pyrimidine DNA bases. Besides the pyrimidines, electrochemically active covalent adducts with Os,bipy are formed also by tryptophan (W) residues in peptides and proteins. In this paper we show that Os,bipy-treated proteins possessing W residues (such as avidin, streptavidin, or lysozyme) yield at the pyrolytic graphite electrode (PGE) a specific signal (peak alphaW) the potential of which differs from the potentials of signals produced by free Os,bipy or by Os,bipy-modified DNA. No such signal is observed with proteins lacking W (such as ribonuclease A or alpha-synuclein). Subpicomole amounts of W-containing proteins modified with Os,bipy can easily be detected using adsorptive transfer stripping voltammetry with the PGE. Binding of biotin to avidin interferes with Os,bipy modification of the protein, in agreement with the location of W residues within the biotin-binding site of avidin. These Ws are accessible for modification in the absence of biotin but hidden (protected from modification) in the avidin-biotin complex. The Os,bipy-modified avidin is unable to bind biotin, and its quarternary structure is disrupted. Analogous effects were observed with another biotin-binding protein, streptavidin. Our results demonstrate that modification of proteins with Os,bipy under conditions close to physiological, followed by a simple electrochemical analysis, can be applied in the microanalysis of protein structure and interactions.

Synthesis and pharmacochemical study of new Cu(II) complexes with thiophen-2-yl saturated and α,β-unsaturated substituted carboxylic acids

Copper complexes with thiophen-2-yl saturated and α,β-unsaturated carboxylic acids as ligands were prepared, characterized and pharmacochemically studied. The available evidence supports a dimeric structure for the complexes of the general formula [Cu 2(L) 4(MeOH) 2] where L are the anions of thiophene 2-carboxylic acid (HL 1), 2-(thiophen-2-yl)-acetic acid (HL 2), 3-thiophen-2-yl-acrylic acid (HL 3), 2-phenyl-3-thiophen-2-yl-acrylic acid (HL 4) respectively. The crystal structure of [Cu 2(L 1) 4(MeOH) 2] ( 2) was determined while preliminary X-ray analysis of the copper complex with L 4 isolated from MeOH/DMSO solution proved to contain three crystallographically independent dimers of the formula [Cu 2(L 4) 4(MeOH)( dmso)][Cu 2(L 4) 4(MeOH) 2][Cu 2(L 4) 4( dmso) 2] · 8MeOH ( 9). Since lipophilicity is a significant physicochemical property determining distribution, bioavailability, metabolic activity and elimination, we tried to measure experimentally their lipophilicity from RPTLC method. The copper complexes and the ligands (thiophen-2-yl saturated and α,β-unsaturated carboxylic acids) were tested in vitro on: (a) soybean lipoxygenase inhibition, (b) interaction with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, (c) the HO mediated oxidation of DMSO, (d) inhibition of lipid peroxidation, (e) scavenging of superoxide anion radicals and in vivo for the inhibition of carrageenin-induced rat paw edema. The compounds have shown important antioxidant activity, significant anti-inflammatory activity and potent inhibition of soybean lipoxygenase as a result of their physichochemical features. Complex [Cu 2(L 1) 4(MeOH) 2] (2) presents the higher in vivo activity (77.4%) followed by complex [Cu 2(L 2) 4(MeOH) 2] ( 4) (51%). Both complexes are more potent anti-inflammatory agents compared to their respective ligands. Moreover we have performed in vitro studies upon their effect on dsDNA, using adsorptive transfer stripping voltammetry and a dsDNA modified carbon paste electrode. Our conclusions were mainly based upon the effect of the studied compounds on the oxidation signal of guanine and adenine. From the given data it seems that complexes show similarities in their behaviour.

Electrochemical determination of Ag-ions in environment waters and their action on plant embryos

We utilized liquid chromatography coupled with electrochemical detector (HPLC–ED) for analyzing of silver ions. The optimization of basic chromatographic parameters has been done. The detection limit (3 S/N) obtained were 20 nmol/dm 3. Influence of different interferences (anions and cations) on current response of silver ions has been described. Moreover, we used HPLC–ED to analyze waters of different purity including photographic emulsion, which naturally contained silver ions. We found out that content of silver ions in the emulsion was 1.57 × 0.03 mmol/dm 3. Moreover, we investigated influence of silver ions on early somatic embryos of Blue Spruce. We were interested in the issue how much silver ions can embryos uptake during four days long treatment. For this purpose, we used optimized HPLC–ED technique. The content increased with increasing treatment time and applied concentration. We also studied how silver ions can influence thiols content in the treated embryos. For these purposes we used adsorptive transfer stripping voltammetry in connection with differential pulse voltammetry — Brdicka reaction. It clearly follows from the obtained results that content of thiols increased with increasing treatment time and applied concentration.

Adsorptive transfer stripping voltammetry applied to the study of the interaction between DNA and actinomycin D

Actinomycin D is an antitumor antibiotic which intercalates within DNA. The interaction of actinomycin D with double-stranded and thermally denatured (single-stranded) calf thymus DNA was studied in solution as well as at the electrode surface using differential pulse transfer voltammetry with carbon paste electrode in 0.2 M acetate buffer, pH 5.0.

Two‐Surface Strategy in Electrochemical DNA Hybridization Assays: Detection of Osmium‐Labeled Target DNA at Carbon Electrodes

AbstractTarget DNAs, including a 71‐mer oligonucleotide, a PCR product and a plasmid DNA, all containing oligo(A) stretches, were hybridized at magnetic Dynabeads oligo(dT)25 (DBT). The hybridization events were detected using a technique based on chemical modification of the target DNA with a complex of osmium tetroxide with 2,2′‐bipyridine (Os, bipy) and voltammetric detection at carbon electrodes. DNA was modified with Os, bipy prior to capture at DBT, at the beads, or after release from the beads. In the latter case, DNA‐Os, bipy was detected in the reaction mixture using adsorptive transfer stripping voltammetry involving extraction of unreacted Os, bipy from the electrode by organic solvents. Pre‐labeling of the target plasmid DNA and the PCR product with Os, bipy significantly increased the yield of DNA captured at the beads. Tens of femtomoles of both short (the 71‐mer oligonucleotide) and long (the 3‐kilobase plasmid) target DNAs in a 20‐microliter hybridization sample can be easily detected by means of these techniques. Various carbon electrode materials, including pyrolytic graphite (PGE), highly oriented pyrolytic graphite (HOPGE), carbon paste (CPE), glassy carbon and pencil graphite, were tested regarding their suitability for the detection of osmium‐labeled DNA. Among them, PGE and HOPGE appeared usable in the measurements of both purified DNA‐Os, bipy and its mixtures with unreacted Os, bipy while CPE was suitable for the detection purified osmium‐labeled DNA.

DNA and PNA sensing on mercury and carbon electrodes by using methylene blue as an electrochemical label

Described here are the electrochemical parameters for MB on binding to DNA at hanging mercury drop electrode (HMDE), glassy carbon electrode (GCE), and carbon paste electrode (CPE) in the solution and at the electrode surface. MB, which interacts with the immobilized calf thymus DNA, was detected by using single-stranded DNA-modified HMDE or CPE (ssDNA-modified HMDE or CPE), bare HMDE or CPE, and double-stranded DNA-modified HMDE or CPE (dsDNA-modified HMDE or CPE) in combination with adsorptive transfer stripping voltammetry (AdTSV), differential pulse voltammetry (DPV), and alternating current voltammetry (ACV) techniques. The structural conformation of DNA and hybridization between synthetic peptide nucleic acid (PNA) and DNA oligonucleotides were determined by the changes in the voltammetric peak of MB. The PNA and DNA probes were also challenged with excessive and equal amount of noncomplementary DNA and a mixture that contained one-base mismatched and target DNA. The partition coefficient was also obtained from the signal of MB with probe, hybrid, and ssDNA-modified GCEs. The effect of probe, target, and ssDNA concentration upon the MB signal was investigated. These results demonstrated that MB could be used as an effective electroactive hybridization indicator for DNA biosensors. Performance characteristics of the sensor are described, along with future prospects.

Adsorptive Transfer Stripping AC Voltammetry of DNA Complexes with Intercalators

Using alternating current adsorptive transfer stripping voltammetry at hanging mercury drop electrode (HMDE), conformational changes of DNA due to binding of DNA intercalators were studied by means of the measurements of tensammetric DNA signals of peak 2 and peak 3. Untwisting of DNA by the intercalators in solution resulted in an altered DNA adsorption. After medium exchange and intercalator removal, the surface-confined DNA probably adopted a restrained structure, with untwisted segments attached to the electrode surface (yielding peak 2) and superhelical loops extending to the bulk of solution. This structure was more resistant to DNA surface denaturation than dsDNA adsorbed at HMDE in the absence of intercalators, which resulted in a decreased intensity of DNA peak 3. Similar effects were also observed when DNA was adsorbed at the electrode from a solution of low salt concentration. Upon introduction of DNA single-strand breaks, the specific behavior of DNA-intercalator complexes was eliminated.

Voltammetric study of khellin at a DNA-coated carbon paste electrode

The pre-concentration and voltammetric detection of khellin in phosphate buffer (pH 7.0) at a DNA-coated carbon paste electrode is described. The anodic wave of khellin intercalated with DNA, covalently immobilized onto the surface of an anodically activated carbon paste electrode, measured in background electrolyte, was utilized for the determination of the drug. The response is characterized with respect to pre-concentration time, scan rate, khellin concentration, and other variables. By differential pulse voltammetry, the calibration plot is linear in the range 5 × 10 −8 to 1 × 10 −7 M with a detection limit of 1 × 10 −8 M. The adsorptive transfer stripping voltammetry approach was utilized for the determination of khellin in doped serum. A method is also developed for the determination of khellin in dosage form.

Voltammetry of native double-stranded, denatured and degraded DNAs

Abstract Degradation of calf thymus and plasmid DNAs was studied by means of conventional as well as adsorptive transfer stripping voltammetry in cyclic and a.c. modes in combination with an HMDE. These techniques detected sensitively small damages to the DNA double helix induced by relatively low doses of ionizing radiation as well as by partial depurination of DNA at a weakly acidic pH in the presence of HNO 2 . Electrochemical analysis did not require any special pretreatment of the sample, and the amount of DNA necessary for this analysis was below 1 μg. It was shown that dissolving DNA in concentrated perchloric acid resulted in a deep DNA degradation including depurination of DNA.

Cyclic voltammetry with RNA-modified mercury electrode

RNA was analyzed by means of cyclic voltammetry (CV) in combination with a hanging mercury drop electrode (HMDE) using conventional adsorptive stripping voltammetry (AdSV) and adsorptive transfer stripping voltammetry (AdTSV) involving the RNA-modified electrode. The immobilization of RNA at HMDE is sufficiently stable and the RNA-modified electrode can be used for analytical purposes. The immobilized tRNA produces a small faradaic cathodic peak CA (due to reduction of adenine and cytosine residues) and an anodic peak G (due to guanine) if a neutral medium containing ammonium ions is used as a background electrolyte. The potentials of peaks CA and G correspond to those of DNA. Peak G can be used for the determination of RNA and DNA in the mixture if RNA is specifically hydrolyzed by ribonuclease A and AdTS CV is performed before and after the enzymatic hydrolysis. The presence of RNase and of the RNA hydrolysate in the analyzed preparation does not interfere with the analysis, which enables AdTS CV to be performed directly with the hydrolyzed sample without any purification or separation steps. In a weakly alkaline background electrolyte tRNA produces a cathodic peak at −1.36 V/SCE which differs by almost 100 mV from the more negative peak of DNA, thus providing the possibility of monitoring RNA and DNA signals in the mixture. Submicrogram amounts of RNA and DNA in a mixture can easily be analyzed in both neutral and alkaline media.

Cyclic voltammetry of submicrogram quantities of supercoiled, linear and denatured DNAs with DNA-modified mercury electrode.

We have previously shown that a DNA-modified electrode can be prepared by immersing the hanging mercury drop electrode (HMDE) in a small volume (about 5-10 microliters) of a DNA solution. Within a short period of time the DNA is irreversibly adsorbed at the electrode, resisting subsequent washing. The electrode is then transferred into a voltammetric cell filled with the background electrolyte (that does not contain any nucleic acid) in which the voltammetric measurements are performed. This procedure is called adsorptive transfer stripping voltammetry (AdTSV). In this paper AdTS cyclic voltammetry (CV) peaks of DNA were measured to report on the stability of the attachment of plasmid DNA molecules to the electrode surface. It was shown that the attachment of plasmid DNA to the electrode was, like the case of calf thymus DNA, sufficiently stable. If the DNA-modified electrode was immersed in a protein solution no significant exchange between the DNA and protein was observed. Submicrogram amounts of DNA were sufficient to attain full coverage of the electrode at relatively short waiting times and the detection limit of the denatured DNA was below 2 ng. The intensity of the AdTS CV signals of supercoiled, linearized and thermally denatured linear DNAs differed from one another. It was shown that alkaline denaturation of linear and supercoiled DNA in solution can be studied using AdTS CV technique. It was further shown that at neutral pH the linearized plasmid undergoes denaturation due to a prolonged contact with the electrode charged to potentials around -1.2 V. Such a surface denaturation has been previously observed with calf thymus DNA and synthetic double-stranded polynucleotides. Our results show that in contrast to linear DNA, supercoiled DNA was not significantly denatured as a result of its prolonged contact with the electrode charged to various potentials in the range between -0.1 to -1.5 V.