Abstract  A novel flow injection analysis (FIA) system suitable for measurement of S-nitrosothiols (RSNOs) in blood plasma is described. In the proposed (FIA) system, samples and standards containing RSNO species are injected into a buffer carrier stream that is mixed with the reagent stream containing 3,3'-dipropionicdiselenide (SeDPA) and glutathione (GSH). SeDPA has been shown previously to catalytically decompose RSNOs in the presence of a reducing agent, such as GSH, to produce nitric oxide (NO). The liberated NO is then detected downstream by an amperometric NO sensor. This sensor is prepared using an electropolymerized m-phenylenediamine (m-PD)/resorcinol and Nafion composite films at the surface of a platinum electrode. Using optimized flow rates and reagent concentrations, detection of various RSNOs at levels in the range of 0.25-20 μM is possible. For plasma samples, detection of background sensor interference levels within the samples must first be carried out using an identical FIA arrangement, but without the added SeDPA and GSH reagents. Subtraction of this background sensor current response allows good analytical recovery of RSNOs spiked into animal plasma samples, with recoveries in the range of 90.4-101.0%.

Abstract  This paper deals with the isolation properties of four relevant wine mercaptans in two different separation systems and with the subsequent development, optimization and validation of an analytical procedure for their quantitative determination. 4-Methyl-4-mercaptopentanone (4M4MP), 2-furanmethanethiol (FFT), 3-mercaptohexanol (3MH) and 3-mercaptohexyl acetate (AMH) can be quantitatively extracted from 200 ml of wine in a bed packed with 1 g of LiChrolut EN resins. Fatty acids and diverse interfering compounds are removed by rinsing with an aqueous solution with a 40% of methanol and buffered at pH 7.2 with alpha,alpha,alpha-tris-(hydroxymethyl)-aminomethane (TRIS) 0.2 M. Mercaptans can be further isolated by extraction with an aqueous solution of 1 mM p-hydroxymercury benzoate. Best results were achieved with an extraction with a solution at pH 10.7 with 0.2 M 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), further acidification to pH 7.5, release of thiols by the addition of dithioerythritol and extraction with 2 x 0.75 ml dichloromethane. The extract is concentrated to 200 and 20 microl are finally injected in a gas chromatograph-ion trap mass spectrometric system. Method detection limits are 0.8, 6, 15 and 5 ng l(-1) for 4M4MP, FFT, MH and AMH, respectively. The recovery in the sample pre-treatment was 76, 45, 75 and 95%, respectively. Repeatability and linearity are also satisfactory. Different critical aspects, such as the effect of air or the evaporation of the extract were also studied.

Abstract  This review paper describes recent developments in both the fundamental and technological aspects of direct methanol fuel cells (DMFCs). Most previous studies in this field have dealt with fundamental aspects, whereas in recent years, the technology of these devices has become the object of significant interest. This is mainly due to the fact that a probable application of DMFCs in portable power sources and in hybrid electrical vehicles has only recently been envisaged. The section on fundamentals is particularly focused on the electrocatalysis of the methanol oxidation reaction and oxygen electroreduction. In this regard, particular relevance is given to the interpretation of the promoting effect on Pt of additional elements and some aspects of the electrocatalysis of oxygen reduction in the presence of methanol crossover have been treated. The technology section deals with the development of both components and devices. Particular emphasis is given to the development of high surface area electrocatalysts and alternative electrolyte membranes to Nafion, also the fabrication methodologies for the M&E assembly have been discussed. The last part of the paper describes the recent efforts in developing DMFC stacks for both portable and electro-traction applications. The current status of the technology in this field is presented and some important technical and economical challenges are been discussed.

Abstract  Methanol crossover from the anode side to the cathode site across the membrane in direct methanol fuel cells causes loss of fuel and catalyst poisoning. Many reports deal with the modification of the commonly used Nafion(R) membrane or the development of new polymer membranes exhibiting reduced methanol permeability. The present study reports on the use of tetra(orthoaminophenyl)porphyrin ((o-NH2)TPP) as the methanol barrier when electropolymerized on a direct methanol fuel cell cathode. Using the electrochemical quartz crystal microbalance and atomic force microscopy techniques, the (poly(o-NH2)TPP) films which efficiently reduced methanol permeability were shown to be non-porous, 0.55 mum thick and characterized by a high density (0.94 g/cm(3)) and high porphyrin site concentration (1.4 M). For a glassy carbon electrode electrodeposited with Pt (Pt/GC), the oxygen reduction current density in 1 M H2SO4 at +0.1 V decreases from 0.42 to 0.23 mA/cm(2) in the presence of 0.5 M methanol while a similar electrode coated with the electropolymerized porphyrin shows almost no decrease after methanol addition (0.58 and 0.56 mA/cm(2), respectively). For Pt/C electrodes with a surface morphology coarser than that of Pt/GC, the surface was first coated with electropolymerized aniline-2-sulfonic acid (PAS) and then with the electropolymerized porphyrin. The ratio of oxygen reduction currents after and before adding 0.25 M methanol was approximately 90% in this case. Experiments in a two-electrode configuration showed that it is possible to operate a DMFC with low current output without using an electrolytic membrane separating the anode from the cathode, provided that the cathode is coated with a bilayer of PAS/poly(o-NH2)TPP. (C) 2004 Elsevier B.V. All rights reserved.

Abstract  1-Anilinonaphthalene-8-sulfonic acid (1,8-ANS), 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) and 2-(p-toluidino)naphthalene-6-sulfonic acid (2,6-TNS) were evaluated as additives in different buffers for the detection of bovine whey proteins using laser-induced fluorescence (LIF) monitoring in capillary electrophoresis (CE). These N-arylaminonaphthalene sulfonates furnish a large fluorescence emission when associated to some proteins whereas their emission in aqueous buffers, such as those used in CE separations, is very small. To select the best detection conditions, the fluorescence of these probes was first compared using experiments carried out in a fluorescence spectrophotometer. Using bovine serum albumin (BSA) as a model protein, it was demonstrated that 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer (pH 8 and pH 10.2) and the fluorescent probe 2,6-TNS gave rise to the highest increase in fluorescence for BSA. When the composition of these separation buffers was optimized for the electrophoretic separations, CHES buffer, pH 10.2 was chosen as the most suitable buffer to detect bovine whey proteins. The limit of detection obtained for some whey proteins in CE separations was about 6.10(-8) M for BSA, 3.10(-7) M for beta-lactoglobulin A (beta-LGA), 3.10(-7) M for beta-lactoglobulin B (beta-LGB), and 3.10(-6) M for alpha-lactalbumin (alpha-LA). These detection limits were compared to those achieved using UV detection under the same separation conditions. The results showed that the detection limits of BSA, beta-LGA and beta-LGB were twice as good using LIF than with UV detection. However, the limit of detection for alpha-LA was better when UV was used. The applicability of LIF detection to CE separation of whey proteins in bovine milk samples was also demonstrated. (C) 1999 Elsevier Science B.V. All rights reserved.

Abstract  This study describes the activity of Pt40%/Vulcan XC-72 carbon catalyst modified with Rb2.5H0.5PW12O40 zeolite-type matrix prepared by a mixing method. The catalyst is used to induce the anodic oxidation of ethanol in an acidic medium as well as to investigate its suitability for use in direct ethanol fuel cells (DEFCs). Under the same Pt-loading, mass, and experimental conditions for ethanol oxidation, the catalysts containing the above mentioned zeolite-type supports display significantly enhanced electrocatalytic activity in comparison to unmodified Pt40%/Vulcan XC-72 carbon. Our new system containing the Nafion-treated rubidium salt of Keggin-type heteropolyacid as a matrix and the Pt40%/Vulcan XC-72 carbon catalyst was characterized with respect to its electrochemical properties and its electrocatalytic activity towards the ethanol oxidation. Results clearly indicate that proposed catalyst containing Rb2.5H0.5PW12O40 (RbPW) matrix is of potential utility to direct ethanol fuel cell.

Abstract  A Continuous Ambient Mass Monitor (CAMM) for fine particle mass (PM2.5) has recently been developed at the Harvard School of Public Health. The principle of this method is based on the measurement of the increase in pressure drop across a membrane filter (Fluoropore(TM)) during particle sampling, The monitor consists of a conventional impactor/inlet to remove particles larger than 2.5 mu m, a diffusion dryer to remove particle-bound water, a filter tape to collect particles, a filter tape transportation system to allow unassisted sampling, and a data acquisition and control unit. For each sampling period (typically 30-60 min), a new segment of the filter tape is exposed so that particles remain close to equilibrium with the sample air during their collection. This results in minimization of volatilization and adsorption artifacts during sampling. Furthermore, since the required how rate for the fine particle mass monitoring channel is only 0.3 L/min, the relative humidity of the air sample can be easily reduced to 40% or less using a Nafion(TM) diffusion dryer to remove particle-bound water, The CAMM has a detection limit of < 5 mu g/m(3) for PM2.5 concentrations averaged over 1 h. The performance of the newly developed monitor was investigated through laboratory and field studies. Laboratory tests included a calibration of the CAMM using polystyrene latex (PSL) and silica particles. A series of field studies were conducted in 7 cities with presumably different PM2.5 chemical composition. The 24 1-h CAMM measurements were averaged and compared to Harvard Impactor (HI) 24 h PM2.5 integrated measurements, Based on 211 valid sampling days, the measurements obtained from the Harvard Impactor and the CAMM were highly correlated (r(2) = 0.90). The average CAMM-to-HI concentration ratio was 1.07 (+/-0.18).

Abstract  We describe the redox behaviour of horse heart cytochrome c (HHC) and Rhodobacter capsulatus cytochrome c peroxidase (RcCCP) at a gold electrode modified with 4,4′-bipyridyl. RcCCP shows no additional oxidation or reduction peaks compared to the electrochemistry of only HHC, which indicates that it most likely binds to HHC and results in a potential downshift of the voltammetric signals of the latter. Furthermore, the electrochemical determination of hydrogen peroxide at a RcCCP/HHC modified gold electrode is shown. The results demonstrate that HHC can substitute for cytochrome c 2, the physiological electron donor. The buffer 2-[4-(2-hydroxyethyl)-piperazinyl] ethanesulfonic acid (HEPES) and tris(hydroxymethyl) methylamine (Tris) electrochemically are not as inert as previously believed. They can react with oxygen (radicals) during electrochemical measurements, and the products formed can give rise to additional redox peaks. We therefore also have conducted a voltammetric study on theses buffers. [ABSTRACT FROM AUTHOR] Copyright of Microchimica Acta is the property of Springer Science & Business Media B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)

Abstract  Because Ru(bpy)32+-modified electrodes are often used in aqueous condition, the development of a hydrophilic modified electrode is of critical importance. Herein a hydrophilic, thin film Ru(bpy)32+-modified electrode is successfully developed using polyacrylamide gel to embed halloysite nanotubes on the electrode surface which is used to adsorb Ru(bpy)32+ by cation-exchange. X-ray photoelectron spectroscopy demonstrates the formation of the film on an electrode and the high adsorbing capacity of the halloysite nanotubes toward Ru(bpy)32+. The different electrochemiluminescence (ECL) behaviors of the electrode using nitrilotriacetic acid and tripropylamine, as co-reactants, illustrate the hydrophilic character of the modified electrode. Contrary to the previous works, the addition of carbon nanotubes into the modified electrode film leads to a decreased ECL emission, due to the reduction in the porosity of the film, which hinders the diffusion of the analyte.

Abstract  Patients with human African trypanosomiasis present a major dysruption of the circadian rhythmicity of the sleep-wake cycle, which was also found in rats infected with Trypanosoma brucei brucei (T.b.b.). The alterations in the immune function and nervous system in African trypsanosomiasis led us to investigate the involvement of nitric oxide (NO), a key molecule in immune and neurophysiological mechanisms, in experimental trypanosomiasis. NO was measured in 35 Sprague Dawley rats using differential impulsional voltammetry with a carbon fiber coated with porphyrin-nickel and nafion, ex vivo in the blood and in vivo in the brain. The rats were anaesthetized with sodium chlorate. Infection was performed intraperitoneally (i.p.) with 0.2 ml of a T.b.b. cryostabilate (clone AnTat 1.1E). Blood was collected by an intracardiac puncture with immediate replacement of blood volume (1 ml) in 7 control rats and 8 rats infected since 15 days, before and after i.p. administration of L-ANA (L-arginine-p-nitro-anilide, 100 mg.kg-1, an inhibitor of NO synthase). Brain measures were done in 20 rats (8 controls, and 12 rats infected since 15 or 21 days), in the cortex (H, -0.5 mm; AP, -0.8 mm; L, 1.2 mm) and the lateral ventricle (H,-3.2 mm). In infected rats, blood NO was at 70% of control values (p < 0.001), and L-ANA suppressed the NO signal in all animals (p < 0.0001), demonstrating that the signal originated from NO. Cortical NO was higher than in the ventricle in both control (p < 0.0001) and infected rats (p < 0.001). NO was more elevated in both structures in 15-day-infected rats than in control rats (p < 0.0001), the difference being enhanced in 21-day-infected rats (p < 0.001). L-ANA suppressed the NO signal in 30 to 60 min. These data suggest that NO intervenes in the development of trypanosomiasis in different manners. It is increased in the brain, which remains unexplained, where it may be involved in blood-brain barrier permeation. Conversely, it is decreased in the blood, may be because of macrophage function impairment, which would explain why trypanosomes can multiply in the host.

Abstract  The conditional stability constant at pH 7.4 for Cu(II) binding at the N-terminal site (NTS) of human serum albumin (HSA) was determined directly by competitive UV-vis spectroscopy titrations using nitrilotriacetic acid (NTA) as the competitor in 100 mM NaCl and 100 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (Hepes). The log Kc (NTS) value of 12.0 +/- 0.1 was determined for HSA dissolved in 100 mM NaCl. A false log log Kc (NTS) (c) value of 11.4 +/- 0.1 was obtained in the 100 mM Hepes buffer, owing to the formation of a ternary Cu(NTA)(Hepes) complex. The impact of the picomolar affinity of HSA for Cu(II) on the availability of these ions in neurodegenerative disorders is briefly discussed.

Abstract  8-Hydroxy-2'-deoxyguanosine (8-OHdG) is a typical biomarker of oxidative DNA damage and has attracted much attention in recent years since the level of 8-OHdG in body fluids is typically associated with various diseases. In this work, a simple and highly sensitive electrochemical sensor for the determination of 8-OHdG was fabricated incorporating single wall carbon nanotubes-(SWCNTs-) Nafion composite film coated on glassy carbon electrode. Nafion was chosen as an optimal adhesive agent from a series of adhesive agents and acted as a binder, enrichment, and exclusion film. Due to the strong cation-exchange ability of Nafion and the outstanding electronic properties ofSWCNTs, the prepared SWCNTs-Nafion film can strongly enhance the electrochemical response to oxidation of 8-OHdG and efficiently alleviate the interferences from uric acid and ascorbic acid. The oxidation peak currents are linear with the concentration of 8-OHdG in the range of 0.03 to 1.25 mu M with a detection limit of 8.0 nM (S/N = 3). This work demonstrates that SWCNTs-Nafion film can improve the sensitivity, selectivity, reproducibility, and stability, making it an ideal candidate for electrochemical detection of 8-OHdG.

Abstract  In recent years, great progress has been made in the development of proton-exchange membrane fuel cells (PEMFCs) for both mobile and stationary applications. This review covers two types of new membranes: (1) carbon dioxide-selective membranes for hydrogen purification and (2) proton-exchange membranes; both of these are crucial to the widespread application of PEMFCs. On hydrogen purification for fuel cells, the new facilitated transport membranes synthesized from incorporating amino groups in polymer networks have shown high CO2 permeability and selectivity versus H-2. The membranes can be used in fuel processing to produce high-purity hydrogen (with less than 10 ppm CO and 10 ppb H2S) for fuel cells. On proton-exchange membranes, the new sulfonated polybenzimidazole copolymer-based membranes can outperform Nafion (R) under various conditions, particularly at high temperatures and low relative humidities. (C) 2010 Society of Chemical Industry

Abstract  Heterostructured Pd-Pt core-shell nanocubes (NCs) are shown to display catalytic activity in the glucose oxidation reaction (GOR), and were employed as non-enzymatic glucose sensors in 0.1 M NaOH(aq) solution. High-angle annular dark-field transmission electron microscopy and line-scanned energy-dispersive X-ray spectroscopy analyses show that the growth of the Pt shell initially occurs via a layer-by-layer mode, but then switches to the island mode. The voids formed between Pt islands contribute to an increase in the electrochemically active surface area. Based on the same catalyst loading mass, the results of Tafel measurements and cyclic voltammetry indicate that the heterostructured Pd-Pt core-shell NCs (typically 32.7 nm in size) display an exchange current density of 1.81 x 10(-2) mA cm(-2) for chemisorption and dehydrogenation of glucose at the onset of the GOR, and an activity of 0.322 mA in the subsequent reaction that causes the formation gluconolactone on the Pt-OH surface. These values are larger than those observed for 7.5-nm Pt nanoparticles (1.51 x 10(-2) mA cm(-2) and 0.187 mA cm(-2), respectively). Additionally, the core-shell NCs exhibit a sensitivity of 170 mu Aa (TM) mM(-1)a (TM) cm(-2) under GOR catalysis conditions, require a potential as low as -0.05 V (vs. Ag/AgCl) which favors selectivity, and have a linear response range that extends from 0.3 to 6.8 mM. The potential of these NCs for use in non-enzymatic sensing of glucose is further exemplified by a successful analysis of spiked calf serum. In our perception, this sensor also has a large potential in glucose fuel cells.

Abstract  The polyaniline doped novel anionic gemini surfactant (PANI/GS) was chemically synthesized by a micellar polymerization process and then characterized in details by X-ray powder diffractometry, scanning electron microscopy, and FTIR spectroscopy. The results show the presence of polyaniline in the emeraldine base was formed by doping with gemini surfactant. The thermal properties of the composites were studied by carrying out thermal gravimetric analysis. The PANI/GS were found to be soluble in common organic solvents such as chloroform as well as DMSO. The antibacterial activity of the obtained PANI/GS was also evaluated against Gram positive bacteria Bacillus subtilis, Gram negative bacteria Escherichia coli and antibiotics (Amoxicillin) using the agar plate. The antibacterial study showed that the PANI/GS was found to be most effective against both B. subtilis and E. coli respectively which was significant compared to the amoxicillin. Beside that thin-layer of PANI/GS onto glassy carbon electrode (GCE) was fabricated with conducting 5% nafion coating agents to fabricate a sensitive and selective Cd2+ ionsic sensor in short response time into the phosphate buffer phase. The fabricated cationic-sensor was exhibited higher sensitivity, large-dynamic concentration ranges, long-term stability, and improved electrochemical performances towards Cd2+ ions. The calibration plot is linear (r(2), 0.9799) over the large Cd2+ concentration ranges (10.0 nM-1.0 mM). The sensitivity and detection limit is calculated as 2.324 A mu A A mu M(-1)cm(-2) and 6.85 nM (signal-to-noise ratio, at a SNR of 3) respectively. These novel efforts are intiated a well-known method for significant cationic sensor development with directly fabricated nanocomposite onto GCE for the detection of hazardous toxins in ecological and environmental fields in huge scales.

[GRAPHICS]

.

Abstract  A novel paper-based potentiometric sensor with an enhanced response for the detection of glucose in biological fluids is presented. The electrode consists on platinum sputtered on a filter paper and a Nafion membrane to immobilize the enzyme glucose oxidase. The response obtained is proportional to the logarithm of the concentration of glucose, with a sensitivity of -119±8mV·decade-1, a linear range that spans from 10-4M to 10-2.5 M and a limit of detection of 10-4.5 M of glucose. It is shown that Nafion increases the sensitivity of the technique while minimizing interferences. Validation with human serum samples shows an excellent agreement when compared to standard methods. This approach can become an interesting alternative for the development of simple and affordable devices for point of care and home-based diagnostics.

Abstract  A functionalized carbon nanotubes paste electrode modified with cross-linked chitosan for the determination of trace amounts of cadmium(II) and mercury(II) by linear anodic stripping voltammetry is described. Under optimal experimental conditions, the peak current was linear in the Cd(II) concentration range from 5.9 x 10(-8) to 1.5 x 10(-6) mol L(-1) with a detection limit of 9.8 x 10(-9) mol L(-1) and, for Hg(II) from 6.7 x 10(-9) to 8.3 x 10(-8) mol L(-1) with a detection limit of 2.4 x 10(-9) mol L(-1). The proposed method was successfully applied for the determination of Hg(II) in natural and industrial wastewater samples. and Cd(II) in sediments, human urine, natural, and industrial wastewater samples. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  A novel platinum decorated CuO nanoleaves were synthesized through a facile co-precipitation method and further utilized as a sensing platform for glucose based on immobilization of Pt-CuO hybrid nanostructures with Nafion matrix. The prepared composites were characterized by X-ray Diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The modified electrode exhibits excellent electrocatalytic activity towards glucose as probed by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Comparing with pure CuO/Nf/GCE, Pt-CuO/Nf/GCE, as non-enzymatic electrode materials, exhibited a good response towards glucose with linear range 2-1000 mu M with a higher sensitivity of 1681.7 mu A mM(-1) cm(-2) and detection limit of 11 mu M. The excellent electrocatalytic performances could be attributed to the Cu(II)/Cu(III) multiple oxidation states system could promote the redox reactions between electrode materials and glucose, and the electroactive sites became more active due to the synergic effect. The results, high sensitivity, excellent selectivity and long term stability showing that, Pt-CuO is a promising material for the future development of nonenzymatic glucose sensors. (C) 2015 The Electrochemical Society. All rights reserved.

Abstract  A novel electrochemical immunosensor for detecting toxoplasma gondii-specific IgM (Tg-IgM) was constructed based on goldmag (Au-Fe(3)O(4)) nanoparticles and graphene sheets (GS). Thionine (Thi), as a mediator, was first electropolymerized on a nafion-GS (Nf-GS) modified electrode. Subsequently, gold nanoparticles (AuNPs) were attached onto the poly-thionine film through π-stacking interactions, and then were used to immobilize toxoplasma gondii antigen (Tg-Ag) for immunosensor fabrication. A sandwich-type immunoassay for Tg-IgM was performed using Au-Fe(3)O(4) labeled anti-IgM-horseradish peroxidase (HRP) as trace label. Electrochemical detection was carried out in the presence of H(2)O(2) as HRP substrate. Using Au-Fe(3)O(4) provided a simple, non-chemical damaging method for regeneration, and enhanced the HRP reduction ability toward H(2)O(2). The AuNPs/Thi/Nf-GS nanocomposite also had good conductivity and biocompatibility, which effectively improved the immunosensor sensitivity. Under optimal conditions, the immunosensor can detect Tg-IgM in two linear ranges from 0.0375 to 1.2 AU mL(-1) and from 2.0 to 18 AU mL(-1) with a detection limit of 0.016 AU mL(-1) (S/N=3). The immunosensor exhibited good reproducibility, stability, and selectivity as well.

Abstract  A novel approach has been developed for a highly sensitive, fast responding and stable monoenzymatic amperometric biosensor for the detection of hydrogen peroxide using coimmobilized the single walled carbon nanotube (SWNT) and methylene blue (MB) into the metal oxide (SnO2) derived organically modified sol-gel glasses (ormosil). Nafion (NAF) was dispersed within the ormosil matrix to enhance the electron transportation in the modified film. Horseradish peroxidase (HRP) was diffusionally adsorbed onto the SWNT/ormosil modified ITO (Indium tin oxide) electrode surface. The SWNT/ormosil-modified electrodes were characterized with scanning electron microscopy (SEM), Atomic Force microscopy (AFM) and UV-vis spectroscopy. Cyclic voltammetry and amperometry measurements were used to study and optimize the performance of the resulting peroxide biosensor. The apparent Michaelis-Menten constant was determined to be 1.6mM. The effect of pH, SWNT content, applied potential and temperature on the peroxide biosensor has been systemically studied. The fabricated biosensor had a fast response of H2O2, less than 5s and excellent linear range of concentration from 5x10(-7) to 1x10(-4)M with the detection limit of 0.3 mu M (S/N=3) under the optimum conditions. These results show that this amperometric biosensor could be used for the measurement of H2O2 in cellular, enzyme systems or cancer cell studies without the help of any fluorescent probes or detection reagents.

Abstract  Nickel nanowrinkles were synthesized by a simple hydrothermal method in one step in the presence of fluoride ions in ethylene glycol. The nanowrinldes were then employed as the modifier of a carbon paste electrode. The kinetics of the charge transfer across the modified electrode/solution interface was studied and the modified electrode was employed to fabricate an amperometric sensor of hydrochlorothiazide. The mechanism and kinetics of the electrocatalytic oxidation of hydrochlorothiazide on the modified electrode surface were studied by cyclic voltammetry and chronoamperometry. An amperometric procedure was developed for determination of hydrochlorothiazide with a sensitivity of 13.50 mA mol(-1) dm(3) cm(-2) and a limit of detection of 21.2 mu mol dm(-3). The method was used for the direct assay of hydrochlorothiazide in human serum samples and hydrochlorothiazide tablets. The sensor had the advantages of sensitivity (guaranteed by a Nafion layer on the sensor surface), high electrocatalytic activity and long-term stability toward hydrochlorothiazide. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  We report the first utilization of copper disk electrodes as suitable cathodic transducer platforms for glucose biosensors. Simple and cheap Cu disk electrodes were fabricated from ordinary electrical cable by cementing into a glass tube with epoxy resin and subsequent polishing to expose the active area. Glucose oxidase was immobilized on the electrode tips by entrapment in dropped and dried polymeric Nafion deposits. At a H2O2 detection potential of -0.15V vs. a reference electrode, the linear response range of fabricated cable Cu glucose biosensors was 20-1500 mu M, with a sensitivity of about 700 nA mu M(-1)cm(-2). Quantitative analysis of glucose-supplemented buffer solutions showed a recovery of 106 +/- 4% (n= 3). The principal advantage of the glucose biosensors described in this study, compared to other options, is the simplicity of the cathodic H2O2 readout, which exploits cheap and readily available electrical cable, without any extra surface modification with catalytically active micro-or nanomaterials. The analytical performance of the biosensor is competitive and suggests potential applications in routine glucose testing, in particular in academic teaching and research laboratories. The work is also a starting point for transfer of the methodology from simple cable Cu electrodes to arrays of miniaturized Cu sensors, using a combination of microlithography, electroforming and molding (LIGA).

Abstract  Src-homology (SH2) domains are an attractive target for the inhibition of specific signalling pathways but pose the challenge of developing a truly specific inhibitor. The G7-18NATE cyclic peptide is reported to specifically inhibit the growth factor receptor bound protein 7 (Grb7) adapter protein, implicated in the progression of several cancer types, via interactions with its SH2 domain. G7-18NATE effectively inhibits the interaction of Grb7 with ErbB3 and focal adhesion kinase in cell lysates and, with the addition of a cell permeability sequence, inhibits the growth and migration of a number of breast cancer cell lines. It is thus a promising lead in the development of therapeutics targeted to Grb7. Here we investigate the degree to which G7-18NATE is specific for the Grb7-SH2 domain compared with closely related SH2 domains including those of Grb10, Grb14, and Grb2 using surface plasmon resonance. We demonstrate that G7-18NATE binds with micromolar binding affinity to Grb7-SH2 domain (K(D)  = 4-6 μm) compared with 50-200 times lower affinity for Grb10, Grb14, and Grb2 but that this specificity depends critically on the presence of phosphate in millimolar concentrations. Other differences in buffer composition, including use of Tris or 2-(N-Morpholino)ethanesulfonic acid or varying the pH, do not impact on the interaction. This suggests that under cellular conditions, G7-18NATE binds with highest affinity to Grb7. In addition, our findings demonstrate that the basis of specificity of G7-18NATE binding to the Grb7-SH2 domain is via other than intrinsic structural features of the protein, representing an unexpected mode of molecular recognition.