Differential Pulse Voltammetry Peak Currents Research Articles

Ultrasensitively electrochemical detection activity of DNA methyltransferase using an autocatalytic and recycling amplification strategy

Herein, we report a novel approach to the ultrasensitive detection of DNA methyltransferase (MTase) in terms of a dual-signal recycling amplification strategy assisted by an autocatalytic and exonuclease III (Exo III). A duplex DNA probe was designed by G-quadruplex-forming oligomer (S1) hybridizing with ferrocene (Fc)-labeled DNA (S2) modified on Au electrode. With DNA adenine methylation (Dam) MTase, the response of the hairpin probe to methylation is methylated. Then it can be cleaved by the methylation-sensitive restriction endonuclease Dpn I, releasing S3. The released S3 sequence hybridizes with the dangling end of S2 sequence, forming a new duplex DNA. Then the Exo III can cleave the S2 sequence step by step, with the release of Fc from the sensing interface and autonomous generation of new secondary S3 for successive hybridization and cleavage. Meanwhile, S1 sequences on the electrode surface are folded into G-quadruplex-hemin complexes by adding K+ and hemin to give a remarkable electrochemical response. Such conformational changes result in the decrease of differential pulse voltammetry (DPV) peak current of Fc and increase of the DPV peak current of G-quadruplex-hemin complexes. The dual-signal changes are linear with the concentration of DNA MTase. This novel, single electrode-based dual-signal assay strategy is superior to previous Dam assays using single electrochemical signal as output.

Fabrication of modified carbon paste electrodes with Ni-doped Lewatit FO36 nano ion exchange resin for simultaneous determination of epinephrine, paracetamol and tryptophan

A novel carbon paste electrode modified with Ni-doped Lewatit FO36 nano ion exchange resin (Ni-LFONRCPE) was fabricated and used as a sensitive electrochemical sensor for simultaneous determination of Epinephrine (EP), Paracetamol (PT) and Tryptophan (TRP). Cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry (DPV) and Chronoamperometry methods were employed to study the behavior of EP, AC and TRP on this modified electrode. DPVs peak currents of EP, PT and TRP increased linearly with their concentrations within the ranges of 7–560μM, 5–580μM and 4–560μM with detection limits 0.45, 0.27 and 0.38μM for EP, PT and TRP, respectively. The diffusion coefficient (D), electron transfer coefficient (α), and heterogeneous rate constant, for oxidation of EP, PT and TRP at the modified electrode surface were also determined. The Ni-LFONRCPE has been applied for the simultaneous determination of EP, PT and TRP in different real samples and the spiked recoveries were in the range of 96–100%.

Porphyran-capped gold nanoparticles modified carbon paste electrode: a simple and efficient electrochemical sensor for the sensitive determination of 5-fluorouracil

The application of carbon paste electrodes modified with porphyran-capped gold nanoparticles (CPE/AuNps-PFR) to detect an important anticancer drug, 5-fluorouracil (5-FU), is described. Gold nanoparticles (AuNps) were synthesized through a green one-pot route, by using porphyran (PFR) (a sulfated polysaccharide extracted from red seaweed) as reducing and stabilizing agent. The reaction temperature and the concentrations of AuCl4− and PFR for AuNps-PFR synthesis were optimized by using a 23 full factorial design with central point assayed in triplicate. The smallest particle size (128.7 nm, obtained by DLS) was achieved by employing a temperature of 70 °C and AuCl4− and PFR concentrations equal to 2.5 mmol L−1 and 0.25 mg mL−1, respectively. The AuNps-PFR nanocomposite was characterized by UV–vis spectroscopy, FTIR, DLS, TEM, XRD and zeta potential, which proved that PFR was effective at reducing and capping the AuNps. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments showed that the nanocomposite could enhance the electrochemical performance of the electrodes, as a consequence of the high conductivity and large surface area presented by the AuNps. The CPE/AuNps-PFR was able to electrocatalyze the oxidation of 5-FU by CV and differential pulse voltammetry (DPV). A linear relationship between the DPV peak currents and 5-FU concentration was verified in the range from 29.9 to 234 μmol L−1 in 0.04 mol L−1 BR buffer solution pH 8.0. Detection and quantification limits were found to be 0.66 and 2.22 μmol L−1, respectively. Besides the good sensitivity, CPE/AuNps-PFR showed reproducibility and did not suffer significant interference from potentially electroative biological compounds. The good analytical performance of the modified electrode was confirmed for determining 5-FU in pharmaceutical formulations, with good percent recoveries (ranging from 96.6 to 101.4%) and an acceptable relative standard deviation (RSD = 2.80%).

Conducting Polymer-Layered Carbon Nanotube as Sensor Interface for Electrochemical Detection of Dacarbazine In-Vitro

A reusable electrochemical sensor ensembling carbon nanotubes and a conducting polymer together is fabricated for the detection of an important anti-cancer drug, dacarbazine (DTIC). A thin film of a conducting polymer, poly(2-amino-1,3,4-thiadiazole) (poly-ATD), is formed on the carbon nanotube paste electrode (CNPE) by employing a potentiodynamic polymerization technique. The fabricated sensor surface has been characterized by FTIR spectroscopy and scanning electron microscopy (SEM) for the structural and chemical properties of the electrode system. The electrochemical capability of the fabricated poly-ATD/CNPE composite electrode for the detection of DTIC is examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopic analysis (EIS), and the poly-ATD/CNPE electrode is found to be efficient for electrocatalytic oxidation of DTIC. Optimization and evaluation of the sensor system are examined by differential pulse voltammetry (DPV). A linear relationship of DTIC concentration over the peak current of DPVs is exhibited over a wide concentration range of 0.05–24.0 μM with a low detection limit (3σ/b) of 35 nM. Steady state current–time analysis experiments under hydrodynamic conditions exhibited a low detection limit of 20 nM, and the analysis time is as low as 10 s. Practical utility of the fabricated poly-ATD/CNPE biosensor for the detection of DTIC directly from artificial urine and pharmaceutical formulations has been demonstrated with very good recovery limits.

Development of Portable Device for Point-of-Care Testing of Tumor Marker

Abstract By combining electrochemical detection technique and electronic technique, a portable device which adopted differential pulse voltammetry (DPV) measurement was developed to meet the needs of high sensitivity and on-site rapid detection of tumor marker. The voltage and current resolution of portable device were 0.8 mV and 1 nA, respectively. Combined with home-made microfluidic paper-based analytical device, carcinoembryonic antigen (CEA) was detected by portable device. Experimental results revealed that the DPV peak currents showed good linear relationship with the logarithm of CEA concentration in the range of 1–500 μg L −1 . The corresponding correlation coefficient was 0.998 and the limit of detection was 10 ng L −1 . According to the principle of specific binding of antibody and antigen with electrochemical detection, CEA concentration could be calculated automatically according to the linear equation. The portable device with the features of high sensitivity and low detection limit could be widely used in the point-of-care testing of tumor marker.

A Nicotinamide Adenine Dinucleotide Dispersed Multi-walled Carbon Nanotubes Electrode for Direct and Selective Electrochemical Detection of Uric Acid.

A nanocomposite platform built with multi-walled carbon nanotubes (MWCNTs) and nicotinamide adenine dinucleotide (NAD(+)) via a noncovalent interaction between the large π systems in NAD(+) molecules and MWCNTs on a glassy carbon substrate was successfully developed for the sensitive and selective detection of uric acid (UA) in the presence of ascorbic acid (AA), dopamine (DA). NAD(+) has an adenine subunit and a nicotinamide subunit, which enabled interaction with the purine subunit of UA through a strong π-π interaction to enhance the specificity of UA. Compared with a bare glassy carbon electrode (GCE) and MWCNTs/GCE, the MWCNTs-NAD(+)/GCE showed a low background current and a remarkable enhancement of the oxidation peak current of UA. Using differential pulse voltammetry (DPV), a high sensitivity for the determination of UA was explored for the MWCNTs-NAD(+) modified electrode. A linear relationship between the DPV peak current of UA and its concentration could be obtained in the range of 0.05 - 10 μM with the detection limit as low as 10 nM (S/N = 3). This present strategy provides a novel and promising platform for the detection of UA in human urine and serum samples.

A carbon nanofiber-based label free immunosensor for high sensitive detection of recombinant bovine somatotropin.

A carbon nanofiber-based label free electrochemical immunosensor for sensitive detection of recombinant bovine somatotropin (rbST) was developed. In this immunosensor design, a mild site-directed antibody immobilization via interaction of boronic acid and oligosaccharide moiety found on Fc region of an antibody was performed to preserve the biological activity of antibody and improve the sensor's sensitivity. Electrochemical characterization of the immunosensor fabrication was carried out by differential pulse voltammetry (DPV) in Fe(CN)6(3-)/Fe(CN)6(4-) probe. A comparison study between different transducer platforms showed carbon nanofiber gave higher current signal response than single-walled carbon nanotube. In this work, calibration curve was obtained from the decrease of DPV peak current of Fe(CN)6(3-)/Fe(CN)6(4-) after immunocomplexed was formed. A linear relationship between DPV current change signal response and rbST concentrations from 1 pg/mL to 10 ng/mL (correlation coefficient of 0.9721) was achieved with detection limit of 1 pg/mL. Our developed immunosensor demonstrated high selectivity in cross-reactivity studies and a good percentage recovery in spiked bovine serum sample.

Simultaneous determination of acetaminophen, dopamine and ascorbic acid using a PbS nanoparticles Schiff base-modified carbon paste electrode

A highly sensitive method was investigated for the simultaneous determination of acetaminophen (AC), dopamine (DA), and ascorbic acid (AA) using a PbS nanoparticles Schiff base-modified carbon paste electrode (PSNSB/CPE). Differential pulse voltammetry peak currents of AC, DA and AA increased linearly with their concentrations within the ranges of 3.30 × 10 −8 –1.58 × 10 −4 M, 5.0 × 10 −8 –1.2 × 10 −4 M and 2.50 × 10 −6 –1.05 × 10 −3 M, respectively, and the detection limits for AC, DA and AA were 5.36 × 10 −9 , 2.45 × 10 −9 and 1.86 × 10 −8 M, respectively. The peak potentials recorded in a phosphate buffer solution (PBS) of pH 4.6 were 0.672, 0.390, and 0.168 V (vs Ag/AgCl) for AC, DA and AA, respectively. The modified electrode was used for the determination of AC, DA, and AA simultaneously in real and synthetic samples.

Simultaneous electroanalysis of isoniazid and uric acid at poly(sulfosalicylic acid)/electroreduced carboxylated graphene modified glassy carbon electrode

Simultaneous electroanalysis of isoniazid and uric acid (UA) was achieved at a poly(sulfosalicylic acid) (PSA) and carboxylated graphene (CG)-modified glassy carbon electrode (GCE). The CG cast-coated on the GCE was cathodically reduced to form electroreduced CG (ERCG), while the PSA was electrochemically synthesized on the ERCG/GCE. Electrochemical quartz crystal microbalance was used to investigate the electrodeposition processes. The surface morphologies and electrochemical properties of the PSA/ERCG/GCE were studied by scanning electron microscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy. The electrochemical behaviors of isoniazid and UA at PSA/ERCG/GCE were investigated by CV and differential pulse voltammetry (DPV), giving well defined and well separated oxidation peaks of isoniazid and UA. The PSA/ERCG/GCE exhibited notably enhanced electro-oxidation signals of isoniazid and UA in NH3-NH4Cl buffer solution (pH 9.0), as compared with bare GCE and PSA/GCE. Under optimum conditions, the DPV peak currents at PSA/ERCG/GCE responded linearly to isoniazid concentration from 0.05 to 15μM and to UA concentration from 0.02 to 15μM, with limits of detection of 12nM for both isoniazid and UA, which is an improvement compared to many other reported techniques. The PSA/ERCG/GCE was successfully applied to the simultaneous determination of isoniazid and UA in urine substrate samples.

Determination of Bisphenol A Using an Electrochemical Sensor Based on a Molecularly Imprinted Polymer-Modified Multiwalled Carbon Nanotube Paste Electrode

A novel electrochemical sensor for bisphenol A was developed through the combination of a molecular imprinting technique with a multiwalled carbon nanotube paste electrode. A molecularly imprinted polymer and nonimprinted polymer were synthesized in the presence and absence of bisphenol A, and then used to prepare the electrode. The bisphenol A imprinted polymer was applied as a selective recognition element in the electrochemical sensor. Differential pulse voltammetry was used to characterize the electrochemical behavior of bisphenol A at the modified electrodes. The results showed that the imprinted sensor had highest response for bisphenol A. Parameters including the carbon paste composition, pH, and adsorption time for the imprinted sensor were optimized. Under the optimized conditions, the differential pulse voltammetry peak current was linear with the concentration of bisphenol A from 0.08 to 100.0 µM, with a detection limit of 0.022 µM. The imprinted sensor for bisphenol A exhibited good selectivity, stability, and reproducibility. This sensor was successfully used for the determination of bisphenol A in real water samples.

Determination of uric acid in human urine by eliminating ascorbic acid interference on copper(II)-polydopamine immobilized electrode surface

The polydopamine (PD) coating was spontaneously formed through simple immersion of glassy carbon (GC) electrode in a dilute aqueous solution of dopamine (DA) at acidic solution (pH=4.5) in the presence of Cu2+. Copper(II) ions were anchored on surface of GC electrode to prepare a PD-Cu(II) modified electrode. The morphology, composition and electrochemical properties of the PD-Cu(II) films were characterized by scanning electron microscopy, energy-dispersive spectrometry, X-ray photoelectron spectroscopy, powder X-ray diffraction, electrochemical impedance spectroscopy and cyclic voltammetry. This modified electrode shows the extraordinary selectivity for electrochemical determination of uric acid (UA) without interference of high concentration of ascorbic acid (AA). Under coexistence of 5mM AA, the differential pulse voltammetry peak current of UA give linear response over the range of 0.06–1.68mM (R2= 0.9934) with detection limit of 24.6μM (S/N=3). Furthermore, the proposed sensor is ideal for the analysis of UA in human urine samples providing satisfactory results.

Selective recognition and electrochemical detection of p-nitrophenol based on a macroporous imprinted polymer containing gold nanoparticles

We have combined the molecular imprinting and the layer-by-layer assembly techniques to obtain molecularly imprint polymers (MIPs) for the electrochemical determination of p-nitrophenol (p-NPh). Silica microspheres functionalized with thiol groups and gold nanoparticles (Au-NPs) were assembled on a gold electrode surface layer by layer. The electrode was then immersed into a solution of pyrrole and p-NPh (the template), and electropolymerization led to the creation of a polymer-modified surface. After the removal of the silica spheres and the template, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) were employed to characterize the surface. The results demonstrated the successful fabrication of macroporous MIPs embedded with Au-NPs on the gold electrode. The effects of monomer concentration and scan rate on the performance of the electrode were optimized. Excellent recognition capacity is found for p-NPh over chemically similar species. The DPV peak current is linearly related to concentration of p-NPh in the 0.1 μM to 1.4 mM range, with a 0.1 μM limit of detection (at S/N = 3).

Sol-Gel Imprinted Polymers Based Electrochemical Sensor for Paracetamol Recognition and Detection

Molecular imprinting and sol-gel technique were combined to develop a molecular imprinted polymer (MIP) based electrochemical sensor in this work. With the successive modification of multi-walled carbon nanotubes (MWNTs) and gold nanoparticles (GNPs), a modified glassy carbon electrode (GCE) was immersed in a sol-gel solution in the presence of paracetamol (PR) for the electropolymerization to fabricate an imprinted sensor. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were employed to characterize the constructed sensor. The factors for the sensor preparation, the electropolymerization potential range, the monomer concentration, and the scan rate for the sensor preparation were optimized. The sensor displayed an excellent recognition capacity toward PR compared with other analogues. Additionally, the DPV peak current was linear to the PR concentration in the range from 8.0 × 10−8 to 5.0 × 10−5 mol/L, with a detection limit of 4.0 × 10−8 mol/L. The prepared sensor also showed satisfactory reproducibility and regeneration capacity.

A tyrosinase biosensor based on ordered mesoporous carbon–Au/l-lysine/Au nanoparticles for simultaneous determination of hydroquinone and catechol

A novel biosensor was developed based on tyrosinase immobilization with ordered mesoporous carbon-Au (OMC-Au), L-lysine membrane and Au nanoparticles on a glassy carbon electrode (GCE). It was applied for the simultaneous determination of dihydroxybenzene isomers using differential pulse voltammetry (DPV). The tyrosinase/OMC-Au/L-lysine/Au film was characterized by scanning electron microscopy (SEM) and impedance spectra. Under optimized conditions, the DPV study results for two isomers, hydroquinone (HQ, 1,4-dihydroxybenzene) and catechol (CC, 1,2-dihydroxybenzene) showed low peak potentials, and the peak-to-peak difference was about 135.85 mV, which ensured the anti-interference ability of the biosensor and made simultaneous detection of dihydroxybenzene isomers possible in real samples. DPV peak currents increased linearly with concentration over the range of 4.0 × 10(-7) to 8.0 × 10(-5) M, and the detection limits of hydroquinone and catechol were 5 × 10(-8) M and 2.5 × 10(-8) M (S/N = 3), respectively. The tyrosinase biosensor exhibited good repeatability and stability. In addition, the response mechanism of enzyme catalysed redox on the OMC-Au/L-lysine/Au film modified electrode based on electrochemical study was discussed. The proposed method could be extended for the development of other enzyme-based biosensors.

Fabrication of a CuS/graphene nanocomposite modified electrode and its application for electrochemical determination of esculetin

In this paper, a CuS/graphene nanocomposite modified glassy carbon electrode (GCE) was successfully constructed and used for determination of esculetin. The electrochemical behavior of esculetin was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the synergistic effect between CuS nanoparticles (NPs) and graphene enhanced the electrochemical response of esculetin. Under optimal conditions, the DPV peak current increased linearly with the esculetin concentration in the range from 1.0 × 10−7 to 1.0 × 10−4 mol L−1, and the detection limit (S/N = 3) was 5.8 × 10−8 mol L−1. Furthermore, a good selectivity with high sensitivity was obtained for the determination of esculetin in real samples.

Voltammetric analysis with the use of a novel electro-polymerised graphene-nafion film modified glassy carbon electrode: Simultaneous analysis of noxious nitroaniline isomers

A new modified electrode was constructed by the electro-polymerization of 7-[(2,4-dihydroxy-5-carboxybenzene)azo]-8-hydroxyquinoline-5-sulfonic acid (DHCBAQS) at a graphene–nafion modified glassy carbon electrode (GCE). The construction process was performed stepwise and at each step the electrochemical characteristics were investigated particularly with respect to the oxidation of the three noxious analytes, 2-nitroaniline (2-NA), 3-nitroaniline (3-NA), 4-nitroaniline (4-NA); the electrode treated with the fluorescence reagent DHCBAQS performed best. At this electrode, the differential pulse voltammetry peak currents of the three isomers increased linearly with their concentrations in the range of 0.05–0.60μgmL−1, respectively, and their corresponding limits of detection (LODs) were all about 0.022μgmL−1. Furthermore, satisfactory results were obtained when this electrode was applied for the simultaneous quantitative analysis of the nitroaniline isomer mixtures by Principal component regression (PCR) and Partial least squares (PLS) as calibration methods (relative prediction error (PRET) – 9.04% and 9.23%) and average recoveries (101.0% and 101.7%), respectively. The above novel poly-DHCBAQS/graphene–nafion/GCE was successfully employed for the simultaneous analysis of the three noxious nitroaniline isomers in water and sewage samples.

An electrochemical method for high sensitive detection of nicotine and its interaction with bovine serum albumin

A sensor based on bovine serum albumin (BSA) and poly-o-phenylenediamine (PoPD) film modified electrode has been developed to study the interaction of BSA with nicotine. Because of the electro-synthesized convenient and the tunable conductivity of polymer, PoPD was used as the electrochemical probe. The interaction of nicotine with BSA was studied by electrochemistry and spectroscopy methods. The binding constant, obtained by differential pulse voltammetry (DPV), was consistent with the fluorescence analysis. The calibration graph for the determination of nicotine was obtained by the decrease of DPV peak current of PoPD in the presence of BSA. This constructed biosensor exhibited two linear relationships with nicotine concentration range of 1.83×10−10 to 1.01×10−3M and a detection limit of 55pM.

Simultaneous determination of phenylhydrazine and hydrazine by a nanostructured electrochemical sensor

In the present paper, the use of a nanostructured electrochemical sensor was described for simultaneous determination of phenylhydrazine (PhH) and hydrazine (HZ). This electrochemical sensor was prepared by a simple and rapid method by modification of carbon paste electrode with a derivative of hydroquinone and TiO2 nanoparticles. The modified electrode showed an excellent character for electrocatalytic oxidation of PhH. Using differential pulse voltammetry, a highly selective and simultaneous determination of PhH and HZ has been explored at the modified electrode. Differential pulse voltammetry peak currents of PhH and HZ increased linearly with their concentration at the ranges of 2.0×10−6 to 1.0×10−3M and 7.5×10−5–1.0×10−3M, respectively and the detection limits for PhH and HZ were 7.5×10−7M and 9.0×10−6M, respectively.

MCM/ZrO2 nanoparticles modified electrode for simultaneous and selective voltammetric determination of epinephrine and acetaminophen

A novel MCM/ZrO2 nanoparticles modified carbon paste electrode (MZ-CPE) was fabricated and used to study the electro oxidation of epinephrine (EP) and acetaminophen (AC) and their mixtures by electrochemical methods. The modified electrode showed electrocatalytic activity toward EP and AC oxidation with a decrease of the overpotential by 173 mV to a less positive potential for EP at the surface of the MZ-CPE and an increase in peak current at pH 7.0. Differential pulse voltammetry peak currents of EP and AC increased linearly with their concentrations in the ranges of 1.0 × 10−6–2.5 × 10−3 and 1.0 × 10−6–2.0 × 10−3 M, respectively, and the detection limits for EP and AC were 5.0 × 10−7 and 4.5 × 10−7 M, respectively.

A novel electrochemical sensor for isocarbophos based on a glassy carbon electrode modified with electropolymerized molecularly imprinted terpolymer

Abstract In this paper, a novel electrochemical sensor with sensitive and selective binding sites for isocarbophos (ICP) detection is reported, which is based on a glassy carbon electrode (GCE) modified with molecularly imprinted terpolymer of poly( o -phenylenediamine-co-gallic acid-co- m -aminobenzoic acid) (p(PD-GA-ABA)) templated with ICP. The surface feature of the p(PD-GA-ABA) modified GCE (MIP/GCE) was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Several important parameters controlling the performance of the MIP/GCE were investigated and optimized. Under optimal conditions, the changes in DPV peak currents of the redox probe, hexacyanoferrate, were linear to ICP concentrations in the range from 7.50 × 10 −8 to 5.00 × 10 −5 M and 5.00 × 10 −5 to 1.00 × 10 −4 M, with the detection limit of 2.01 × 10 −8 M (S/N = 3). The method was applied successfully to determine ICP in cabbage and cowpea samples with satisfactory precision (2.30–5.28% of RSD) and acceptable recoveries (95.5–110.0%), demonstrating a promising feature for applying the MIP sensor to the measurement of ICP in real samples.