A novel modified carbon paste electrode based on NiO/CNTs nanocomposite and (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol as a mediator for simultaneous determination of cysteamine, nicotinamide adenine dinucleotide and folic acid

An electrochemical immunosensing method for detecting melanoma cells

An electrochemical immunosensing method was developed to detect melanoma cells based on the affinity between cell surface melanocortin 1 receptor (MC1R) antigen and anti-MC1R antibody (MC1R-Ab). The MC1R-Abs were immobilized in amino-functionalized silica nanoparticles (n-SiNPs)-polypyrrole (PPy) nanocomposite modified on working electrode surface of screen-printed electrode (SPE). Cyclic voltammetry was employed, with the help of redox mediator ([Fe(CN)6](3-)), to measure the change in anodic oxidation peak current arising due to the specific interaction between MC1R antigens and MC1R-Abs when the target melanoma cells are present in the sample. Various factors affecting the sensor performance, such as the amount of MC1R-Abs loaded, incubation time with the target melanoma cells, the presence of interfering non-melanoma cells, were tested and optimized over different expected melanoma cell loads in the range of 50-7500 cells/2.5 mL. The immunosensor is highly sensitive (20 cells/mL), specific, and reproducible, and the antibody-loaded electrode in ready-to-use stage is stable over two weeks. Thus, in conjunction with a microfluidic lab-on-a-chip device our electrochemical immunosensing approach may be suitable for highly sensitive, selective, and rapid detection of circulating tumor cells (CTCs) in blood samples.

Rapid and fast strategy for the determination of glutathione in the presence of vitamin B6in biological and pharmaceutical samples using a nanostructure based electrochemical sensor

In this study, we describe the simultaneous determination of glutathione and vitamin B₆in pharmaceutical and biological samples for the first time.

Fabrication of a non-enzymatic Ni(ii) loaded ZSM-5 nanozeolite and multi-walled carbon nanotubes paste electrode as a glucose electrochemical sensor

A template-free ZSM-5 nanozeolite was synthesized and then carbon paste electrode (CPE) was modified by ZSM-5 nanozeolite, multi-walled carbon nanotubes and Ni²⁺ and was used as catalyst for the electrooxidation of glucose (EC′ mechanism).

Chemical etching of bovine serum albumin-protected Au25 nanoclusters for label-free and separation-free detection of cysteamine

This study describes a novel Au nanocluster-based fluorescent sensor for label-free, separation-free and selective detection of cysteamine (CSH). The sensing mechanism is based on CSH etching-induced fluorescence quenching of the bovine serum albumin-protected Au25 nanoclusters (BSAGNCs). A series of characterizations is carried out towards a better understanding of the CSH-induced fluorescence quenching of the BSAGNCs. It is found that CSH can etch the Au25 nanoclusters, exhibiting the potent etching activity. Other thiol-containing compounds such as glutathione and cysteine and other 19 natural amino acids do not interfere with such CSH-induced etching process. The decreases in fluorescence intensity of the BSAGNCs allow sensitive detection of free CSH in the range of 500-10,000nM. The detection limit for CSH is 150nM (S/N=3). The spiked human serum samples can be analyzed with satisfactory results.

Application of CdO nanoparticle ionic liquid modified carbon paste electrode as a high sensitive biosensor for square wave voltammetric determination of NADH

In this paper we report the synthesis and application of CdO nanoparticle (CdO/NPs) and 1,3-dipropylimidazolium bromide as high sensitive sensors for voltammetric determination of nicotinamide adenine dinucleotide (NADH) using carbon paste electrode. The cyclic voltammogram showed an irreversible oxidation peak at 0.68 V (vs. Ag/AgClsat), which corresponded to the oxidation of NADH. Compared to common carbon paste electrode, the electrochemical response was greatly improved for NADH electrooxidation at a surface of CdO/NP modified ionic liquid carbon paste electrode (IL/CdO/NP/CPE). The linear response range and detection limit were found to be 0.09-750 μmol L(-1) and 0.05 μmol L(-1), respectively. Result shows that other physiological species did not interfere in the determination of NADH at the surface of the proposed sensor in the optimum condition. The proposed sensor was successfully applied for the determination of NADH in tap water, urine and pharmaceutical serum samples.

Detecting multiple cell-secreted cytokines from the same aptamer-functionalized electrode

Inflammatory cytokines are secreted by immune cells in response to infection or injury. Quantification of multiple cytokines in parallel may help with disease diagnosis by illuminating inflammatory pathways related to disease onset and progression. This paper describes development of an electrochemical aptasensor for simultaneous detection of two important inflammatory cytokines, interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To enable multiplexing, IFN-γ and TNF-α aptamers were labeled with anthraquinone (AQ) and methylene blue (MB) redox reporters respectively. Random immobilization of two aptamer on gold exhibited redox peaks at -0.37 V (AQ) and -0.15 V (MB) vs. Ag/AgCl reference. When challenged with either IFN-γ or TNF-α, redox signal of the appropriate reporter changed in concentration dependent manner. To demonstrate one possible application of this sensing approach, electrodes were integrated into microfluidic devices and used to dynamically monitor cytokine release from immune cells. Two cell types, primary human CD4 T-cells and U937 monocytic cells, were used to compare differences in cytokine secretions upon stimulation. These cells were infused into the microfluidic devices and stimulated to commence cytokine production. Release of IFN-γ and TNF-α was monitored concurrently from the same small group of cells over the course of 2h. The strategy of encoding specific aptamer types with unique redox reporters allows sensitive and specific detection of multiple protein biomarkers from the same electrode.

An electrochemical nanocomposite modified carbon paste electrode as a sensor for simultaneous determination of hydrazine and phenol in water and wastewater samples

In this study, we report preparation of a high sensitive electrochemical sensor for determination of hydrazine in the presence of phenol in water and wastewater samples. In the first step, we describe synthesis and characterization of ZnO/CNTs nanocomposite with different methods such as transmission electron microscopy (TEM) and X-ray diffraction (XRD). In the second step, application of the synthesis nanocomposite describes the preparation of carbon paste electrode modified with N-(4-hydroxyphenyl)-3,5-dinitrobenzamide as a high sensitive and selective voltammetric sensor for determination of hydrazine and phenol in water and wastewater samples. The mediated oxidation of hydrazine at the modified electrode was investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k) and diffusion coefficient (D) for hydrazine were calculated. Square wave voltammetry (SWV) of hydrazine at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 8.0 nmol L(-1). SWV was used for simultaneous determination of hydrazine and phenol at the modified electrode and quantitation of hydrazine and phenol in some real samples by the standard addition method.

Electropolymerization of taurine on gold surface and its sensory application for determination of captopril in undiluted human serum

Polytaurine film was electrodeposited on gold (Au) electrode through cyclic voltammetry from taurine and phosphate buffer solution. The electrocatalytic effect of polytaurine modified Au (PT/Au) electrode was investigated for electro-oxidation of captopril (CAP). Electrocatalytical activity of PT/Au electrode was studied using cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). DPV was used to evaluate the analytical performance of CAP in the presence of phosphate buffer solution and good limit of detection was obtained by this sensor. The experimental conditions influencing the determination of CAP were optimized and under optimal conditions, the oxidation peak current was proportional to CAP concentration in the range of 0.06-0.2 μM, while the detection limit was 0.03 μM (S/N=3). The results revealed that PT promotes the rate of oxidation by increasing the peak current. Finally, the applicability of the method to direct assay of human serum is described. The proposed sensor was successfully applied to determine cadaverine in fish samples, yielding satisfactory results. The spiked recoveries were in the range of 96.0-105.0%.

A CV Study of Copper Complexation with Guanine Using Glassy Carbon Electrode in Aqueous Medium

Voltammetric behaviors of Copper (II) nitrogen bearing nucleobases, such as Guanine (C5H4N5O2) was studied in electro analyzer using cyclic voltammetry (CV) on a Glassy Carbon Electrode. Assessment of the chemical and physical conditions that may favor optimum current enhancement was done by studying the effect of variation of concentration of metal and ligand ions, variation of scan rate, variation of step height, variation of pH values, and variation of supporting electrolyte as (NH4)2SO4, KCl, and NaCl. It was observed that Copper and Guanine forms a 1 : 2 ratio complex. The work reflects that increasing the concentration of either metal ion or ligand ion increases the corresponding current. Increasing the scan rate increases the corresponding current linearly with the square root of the scan rate. As the step height decreases the peaks become sharp. Anodic and cathodic current increases linearly with decreasing step height. For the complex mixture the complexation occurs maximum at a pH of 2.3–7.0 and is badly restricted in the slightly alkaline medium and the complexing order of the supporting electrolyte showed a trend as (NH4)2SO4>NaCl>KCl.

A voltammetric sensor based on NiO/CNTs ionic liquid carbon paste electrode for determination of morphine in the presence of diclofenac

A novel ionic liquid modified NiO/CNTs carbon paste electrode (IL/NiO/CNTCPE) had been fabricated by using hydrophilic ionic liquid 1-methyl-3-butylimidazolium chloride [MBIDZ]Cl as a binder. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgCl(sat)), which corresponded to the oxidation of morphine. Compared to common carbon paste electrode, the electrochemical response was greatly improved for morphine electrooxidation. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of morphine and diclofenac. Detection limit of morphine was found to be 0.01 μM using square wave voltammetry (SWV) method. The proposed sensor was successfully applied for the determination of morphine in human urine and pharmaceutical samples.

Fabrication of a simple and sensitive QDs-based electrochemiluminescence immunosensor using a nanostructured composite material for the detection of tumor markers alpha-fetoprotein

A simple label-free electrochemiluminescence immunosensor was fabricated for detection of alpha-fetoprotein (AFP) based on a nanostructured composite material (PICA–MWNT) with 2-aminoethanethiol modified CdSe nanoclusters as luminescent particles.