The chronoamperometric and voltammetric behaviour of glutathione at screen-printed carbon micro-band electrodes modified with cobalt phthalocyanine

Screen-printed carbon electrodes (SPCEs) incorporating the electrocatalyst cobalt phthalocyanine (CoPC) have been successfully used for the manufacture of microband electrodes for the determination of reduced glutathione (GSH). Initially investigations were performed to explore the cyclic voltammetric behaviour of these electrodes with potassium ferrocyanide. It was shown that steady state behaviour occurred which is indicative of radial diffusion at a microelectrode. Current densities of 2173 μAcm-2 were obtained compared to 464.4 μAcm-2 for conventional sized (3 mm x 3 mm) screen-printed electrodes were obtained. At scan rates between 5 and 20 mV/s no significant increase in current response was observed. The application of these microband CoPC–SPCEs, to the measurement of GSH by both chronoamperometry and cyclic voltammetry was investigated. The chronoamperometric response was found to be linear between 50 µM and 8.0 mM with a detection limit of 7.3 µM using an applied potential of +0.25 V (vs. Ag/AgCl)

Electrochemical detection of benzodiazepines, following liquid chromatography, for applications in pharmaceutical, biomedical and forensic investigations

Benzodiazepines are an important class of drugs commonly administered with a potential for abuse and environmental pollution. This review focuses on the liquid chromatographic electrochemical detection of the benzodiazepine class of drugs. These are characterised by a readily electrochemically reducible azomethine group, with a number also substituted by other electrochemically active groups. Liquid chromatography employing both single and dual electrode detection has been reported for a variety of benzodiazepines and their metabolites in biological, pharmaceutical, biomedical and forensic investigations. Recently, electrochemistry has been utilised to mimic biological oxidation processes and has been combined with liquid chromatography/mass spectroscopy for their identification and quantification of the products generated. The present review focuses on recent developments in liquid chromatographic- electrochemical determination of benzodiazepines reported since 2006, with earlier reports given in summary

Bleomycin increases neutrophil adhesion to human vascular endothelial cells independently of upregulation of ICAM-1 and E-selectin

© 2016 Taylor & Francis. Aim of the Study: Bleomycin-induced lung disease is a serious complication of therapy characterized by alveolar injury, cytokine release, inflammatory cell recruitment, and eventually pulmonary fibrosis. The mechanisms underlying bleomycin-induced pulmonary fibrosis may be relevant to other progressive scarring diseases of the lungs. Pulmonary vascular endothelial cells are critically involved in immune cell extravasation at sites of injury through adhesion molecule expression and cytokine release. We sought to determine the effects of bleomycin on adhesion molecule expression and cytokine release by pulmonary vascular endothelial cells, and their functional relevance to inflammatory cell recruitment. Materials and Methods: The effects of pharmacologically relevant concentrations of bleomycin on adhesion molecule expression and cytokine release by human vascular endothelial cells in vitro were studied by flow cytometry, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay. A flow chamber model was used to assess the functional consequences on adhesion of flowing human neutrophils to endothelial cell monolayers. Results: Bleomycin increased intercellular adhesion molecule 1 (ICAM-1; CD54), vascular cell adhesion molecule (VCAM-1; CD106), and E-selectin (CD62E) expression, and increased monocyte chemoattractant protein (MCP-1) and interleukin (IL-8) release by endothelial cells. Increases in protein expression were accompanied by increased mRNA transcription. In contrast, there was no direct effect of bleomycin on the profibrotic cytokines transforming growth factor-beta (TGF-β), platelet-derived growth factor-BB (PDGF-BB), or endothelin-1. Under flow conditions, endothelial cells exposed to bleomycin supported increased neutrophil adhesion which was independent of ICAM-1 or E-selectin. Conclusion: Our findings demonstrate that bleomycin promotes endothelial-mediated inflammation and neutrophil adhesion. These mechanisms may contribute to the development of pulmonary fibrosis by supporting immune cell recruitment in the lungs

Development of a simple, low cost chronoamperometric assay for fructose based on a commercial graphite-nanoparticle modified screen-printed carbon electrode

© 2017 Elsevier Ltd This paper describes the development of a simple, low cost chronoamperometric assay, for the measurement of fructose, using a graphite-nanoparticle modified screen-printed electrode (SPCE-G-COOH). Cyclic voltammetry showed that the response of the SPCE-G-COOH enhanced the sensitivity and precision, towards the enzymatically generated ferrocyanide species, over a plain SPCE; therefore the former was employed in subsequent studies. Calibration studies were carried out using chronoamperometry with a 40 µl mixture containing fructose, mediator and FDH, deposited onto the SPCE-G-COOH. The response was linear from 0.1 mM to 1.0 mM. A commercial fruit juice sample was analysed using the developed assay and the fructose concentration was calculated to be 477 mM with a precision of 3.03% (n = 5). Following fortification (477 mM fructose) the mean recovery was found to be 97.12% with a coefficient of variation of 6.42% (n = 5); consequently, the method holds promise for the analysis of commercial fruit juices

Gray Wolves

Wolf conflicts are primarily related to predation on livestock, pets and other domestic animals, as well as their direct and indirect impacts on native ungulates (i.e., big game). Economic losses vary widely with some livestock producers facing high levels of depredation in some areas. This publication focuses on wolf ecology, damage, and management, particularly as it relates to wolf depredation on livestock and other conflicts with people. Wolves and people share the same environments more than people realize. In the U.S., wolves are not confined to wilderness areas. Though curious, wolves generally fear people and rarely pose a threat to human safety. Wolf attacks on people are, and always have been, very rare compared to other wildlife species. However, there have been several cases of human injuries and a few deaths due to wolves in North America over the past 100 years. The main factors contributing to these incidents were habituation to people, rabies infections, conditioning to human foods, and the presence of domestic dogs. It is unusual for wild wolves to associate or interact with people, linger near buildings, livestock, or domestic dogs, but it does occur especially in areas of high wolf densities in and around rural communities. This type of behavior may be more prevalent in areas where wolves are not legally harvested. This “bold” behavior is more typical of a habituated or food- conditioned animal, a released captive wolf, or a released wolf-dog hybrid. The scale and scope of wolf depredation on livestock depends on local wolf density; numbers and kinds of livestock; livestock husbandry practices; availability and vulnerability of alternative prey; human density; road density; severity of winters; and local hunting pressure. In many instances, wolves live around livestock without causing damage or only occasional damage. Wolf pack size has been shown to increase the likelihood of depredations on domestic animals, with larger packs more likely to cause damage. Most losses occur between April and October when livestock are on summer pastures or grazing allotments. Cattle, especially calves, are the most common livestock killed by wolves. When wolves kill sheep or domestic poultry, often multiple individuals are killed or injured. As of 2019, stable wolf populations exist in many regions in the U.S., including Alaska, Minnesota, Wisconsin, Michigan, Wyoming, Montana, and Idaho, with growing populations in parts of Oregon and Washington (Figures 19, 20). Wolves have recently been documented in northern California and northwestern Colorado. A small population of introduced Mexican wolves exists in Arizona and New Mexico, and a small population of red wolves exists in eastern North Carolina. Both the Mexican and red wolf populations are considered more vulnerable to extinction than other North American wolf populations

Development of a disposable screen-printed amperometric biosensor based on glutamate dehydrogenase, for the determination of glutamate in clinical and food applications

A screen printed carbon electrode (SPCE) containing the electrocatalyst Meldola’s Blue (MB) has been investigated as the base transducer for a glutamate biosensor. The sandwich biosensor was fabricated by firstly depositing a chitosan (CHIT) layer onto the surface of the transducer (MB-SPCE), followed by glutamate dehydrogenase (GLDH): this device is designated GLDH-CHIT-MB-SPCE. NAD+ was added to buffer solutions prior to the measurement of glutamate. This biosensor was used in conjunction with amperometry in stirred solution at an applied potential of +0.1 V (vs. Ag/AgCl). Optimum conditions for the analysis of glutamate were found to be as follows: temperature, 35°C; buffer, pH 7; ionic strength, 75 mM; NAD+, 4 mM; CHIT 0.05% in 0.05 M HCl; GLDH, 30 U. The linear range of the biosensor was found to be 12.5 µM to 150 µM, the calculated limit of detection (based on three times signal to noise ratio) was 1.5 µM and the sensitivity was 0.44 nA/µM. The proposed biosensor was used to measure glutamate in serum before and after fortification with glutamate. The endogenous concentration of glutamate was found to be 1.68 mM and the coefficient of variation (CV) was 4.1%. The serum was then fortified with 2 mM of glutamate, and the resulting mean recovery was 96% with a CV of 3.3% (n = 6). An unfiltered beef OXO cube was analysed for monosodium glutamate (MSG) content. The endogenous content of MSG was 124.80 mg/g with a CV of 8.06%. The OXO cube solution was fortified with 0.935g (100 mM) of glutamate, the resulting mean recovery was 91% with a CV of 6.40 %

Freshwater reservoir offsets and food crusts: Isotope, AMS, and lipid analyses of experimental cooking residues

Freshwater reservoir offsets (FROs) occur when AMS dates on charred, encrusted food residues on pottery predate a pot’s chronological context because of the presence of ancient carbon from aquatic resources such as fish. Research over the past two decades has demonstrated that FROs vary widely within and between water bodies and between fish in those water bodies. Lipid analyses have identified aquatic biomarkers that can be extracted from cooking residues as potential evidence for FROs. However, lacking has been efforts to determine empirically how much fish with FROs needs to be cooked in a pot with other resources to result in significant FRO on encrusted cooking residue and what percentage of fish C in a residue is needed to result in the recovery of aquatic biomarkers. Here we provide preliminary assessments of both issues. Our results indicate that in historically-contingent, high alkalinity environments\u3c20%C from fish may result in a statistically significant FRO, but that biomarkers for aquatic resources may be present in the absence of a significant FRO

A novel electroanalytical approach to the measurement of B vitamins in food supplements based on screen-printed carbon sensors

© 2017 Elsevier B.V. This paper describes the development of a novel electrochemical assay for the measurement of water-soluble vitamins in food and pharmaceutical products. The optimum conditions for the determination of vitamin B1 (thiamine), B2 (riboflavin) and B6 (pyridoxine) in phosphate buffer were established using cyclic voltammetry in conjunction with screen printed carbon electrodes (SPCEs). The optimum current response for all three vitamins was achieved in 0.1 M phosphate buffer pH 11 using an initial potential of −1.0 V. Using square wave voltammetry, the linear ranges for thiamine, riboflavin, and pyridoxine were found to be: 15–110 µg/ml, 0.1–20 µg/ml, and 2–80 µg/ml respectively. The application of the method to a commercial food product yielded a recovery of 95.78% for riboflavin, with a coefficient of variation (CV) of 3.38% (n = 5). The method was also applied to a multi-vitamin supplement for the simultaneous determination of thiamine, riboflavin and pyridoxine. In both cases only simple dilution with buffer followed by centrifugation was required prior to analysis. The resulting square wave voltammetric signals were completely resolved with Ep values of −0.7 V, +0.2 V, and +0.6 V respectively. The recoveries determined for the vitamin B complex in a commercial supplement product were found to be 110%, 114%, and 112% respectively (CV = 7.14%, 6.28%. 5.66% respectively, n = 5)

Hydrogenation and dehydrogenation of Tetralin and Naphthalene to explore heavy oil upgrading using NiMo/Al₂O₃ and CoMo/Al₂O₃ catalysts heated with steel balls via induction

This paper reports the hydrogenation and dehydrogenation of tetralin and naphthalene as model reactions that mimic polyaromatic compounds found in heavy oil. The focus is to explore complex heavy oil upgrading using NiMo/Al2O3 and CoMo/Al2O3 catalysts heated inductively with 3 mm steel balls. The application is to augment and create uniform temperature in the vicinity of the CAtalytic upgrading PRocess In-situ (CAPRI) combined with the Toe-to-Heel Air Injection (THAI) process. The effect of temperature in the range of 210–380 °C and flowrate of 1–3 mL/min were studied at catalyst/steel balls 70% (v/v), pressure 18 bar, and gas flowrate 200 mL/min (H2 or N2). The fixed bed kinetics data were described with a first-order rate equation and an assumed plug flow model. It was found that Ni metal showed higher hydrogenation/dehydrogenation functionality than Co. As the reaction temperature increased from 210 to 300 °C, naphthalene hydrogenation increased, while further temperature increases to 380 °C caused a decrease. The apparent activation energy achieved for naphthalene hydrogenation was 16.3 kJ/mol. The rate of naphthalene hydrogenation was faster than tetralin with the rate constant in the ratio of 1:2.5 (tetralin/naphthalene). It was demonstrated that an inductively heated mixed catalytic bed had a smaller temperature gradient between the catalyst and the surrounding fluid than the conventional heated one. This favored endothermic tetralin dehydrogenation rather than exothermic naphthalene hydrogenation. It was also found that tetralin dehydrogenation produced six times more coke and caused more catalyst pore plugging than naphthalene hydrogenation. Hence, hydrogen addition enhanced the desorption of products from the catalyst surface and reduced coke formation

Design and development of novel screen-printed microelectrode and microbiosensor arrays fabricated using ultrafast pulsed laser ablation

© 2016 Elsevier B.V. All rights reserved. A new generic platform for the development of microbiosensors combining screen-printing and ultrafast pulsed laser technologies has been developed, characterised and evaluated. This new platform consists of a layer of screen-printed carbon ink containing the enzyme and mediator, covered with an insulating layer formed from a dielectric screen printed ink. Microholes were drilled through the insulated layer by ultrafast pulsed laser ablation to generate the microbiosensor array. The geometry of the microelectrode array was evaluated by optical microscopy, white light surface profiling and scanning electron microscopy. The electrochemical behaviour of the microelectrode array was characterised by cyclic voltammetry and compared with macroelectrodes. The analytical performance of the microbiosensor array was evaluated with external counter and reference electrodes for hydrogen peroxide and glucose determination showing linearity up to 4 mmol L-1 and 20 mmol L-1 (360 mg dL-1) respectively. The full screen printed three-electrode configuration shows linearity for glucose determination up to 20 mmol L-1 (360 mg dL-1). This study provides a new fabrication method for microelectrode and microbiosensor arrays capable for the first time to retain the activity of the enzymatic system after processing by pulse laser ablation