Abstract  Transition-metal nanomaterials are very important to non-enzymatic glucose sensing because of their excellent electrocatalytic ability, good selectivity, the fact that they are not easily interfered with by chloride ion (Cl-), and low cost. However, the linear detection range needs to be expanded. In this paper, Cu2O-bovine serum albumin (BSA) core-shell nanoparticles (NPs) were synthesized for the first time in air at room temperature by a facile and green route. The structure and morphology of Cu2O-BSA NPs were characterized. The as-prepared Cu2O-BSA NPs were used to modify the glassy carbon electrode (GCE) in a Nafion matrix. By using cyclic voltammetry (CV), the influence from scanning speed, concentration of NaOH, and load of Cu2O-BSA NPs for the modified electrodes was probed. Cu2O-BSA NPs showed direct electrocatalytic activity for the oxidation of glucose in 50 mM NaOH solution at 0.6 V. The chronoamperometry result showed this constructing sensor in the detection of glucose with a lowest detection limit of 0.4 μM, a linear detection range up to 10 mM, a high sensitivity of 1144.81 μAmM-1cm-2 and reliable anti-interference property to Cl-, uric acid (UA), ascorbic acid (AA), and acetaminophen (AP). Cu2O-BSA NPs are promising nanostructures for the fabrication of non-enzymatic glucose electrochemical sensing devices.

Abstract  Sulfonated poly ether ether ketone (SPEEK) has high potential for proton exchange membrane fuel cell (PEMFC) application and has been widely considered as most promising alternative to commercial membranes. In this study a novel ternary composite membrane consisting of SPEEK/poly (vinyl alcohol) (PVA) and tetraethyl ortosilicate (TEOS) were prepared by blending and casting method. The obtained samples were characterized by FT-IR, dynamic mechanical analysis (DMA), electrochemical impedance spectroscopy (EIS), oxidative and hydrolytic stability, water uptake capacity, swelling property and ion exchange capacity tests. According to these characterization test results, the addition of PVA in the membrane structure increased the mechanical strength and in addition TEOS is easily incorporated into the membrane structure because of the presence of modifiable groups in PVA. The addition of TEOS to blend membranes prevented water loss at high temperatures and TEOS addition indirectly increased the proton conductivity of the membranes. The highest performance of 600 mA/cm2 was obtained SP90/PV10/TE coded membrane at 0.6 V cell potential and fuel cell operate at 1 atm and 80 °C. At the same conditions Nafion 117 gave 400 mA/cm2. This study shows that blend membrane seems to be a promising alternative membrane for PEMFC application. © 2018 Elsevier Ltd

Abstract  The Cytosensor(TM) microphysiometer has been modified by incorporating several platinum electrodes into the plunger head. The electrodes have been used to measure simultaneously the change in extracellular oxygen consumption rates and extracellular acidification rates during addition of various non-physiologic agents: 2-deoxy-D-glucose, sodium fluoride, paraoxon-ethyl, and antimycin A. Measurement of two parameters, oxygen and acidification, enables investigation of the aerobic and anaerobic metabolic consequences of these agents. Nation membranes cast onto the platinum electrodes were useful in minimizing adsorption of cell-related interferents. (C) 2003 Published by Elsevier B.V.

Abstract  Hydrogen sulfide (H2S) has recently been recognized as an important physiologically relevant gasotransmitter. Produced by the enzymes involved in the transsulfuration pathway, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), H2S has been implicated to control biological activity in virtually every organ system. In recent years it is being recognized that many commonly used H2S assays do not measure free H2S specifically and may be prone to artifacts. This has led to large variations in the reported H2S biological concentrations. In order to accurately study H2S's functions in biological systems accurate assays which measure free H2S specifically are required. In this work we present a simple microplate-based colorimetric assay for H2S gas. The underside of a 96-well microplate cover was coated with Nafion polymer doped with Ag(+) ions. H2S is a highly volatile gas, and as it is volatilized in the microplate well it reacts with Ag(+) to produce Ag2S nanoparticles, which have a strong absorbance in the low-UV range. By monitoring the absorbance change from formation of Ag2S nanoparticles, H2S production can be monitored in real time. The assay has a limit of detection (LOD) of 2.61 nmol (8.70 μM) and a liner range up to 30 nmol (100 μM). Using the assay, the KM and Vmax of recombinant CSE enzyme were determined to be 11.13 ± 0.57 mM and 0.45 ± 0.01 nmol min(-1), respectively. H2S production from mouse liver homogenate under aerobic conditions in the presence of cysteine was measured and determined to be 4.89 ± 0.19 nmol min(-1) mL(-1) homogenate. The assay is simple, low cost, and specific to free H2S gas.

Abstract  Proton-exchange membranes (PEM) display unique ion-selective transport that has enabled a breakthrough in high-performance proton-exchange membrane fuel cells (PEMFCs). Elemental understanding of the morphology and proton transport mechanisms of the commercially available Nafion® has promoted a majority of researchers to tune proton conductive channels (PCCs). Specifically, knowledge of the morphology-property relationship gained from statistical and segmented copolymer PEMs has highlighted the importance of the alignment of PCCs. Furthermore, increasing efforts in fabricating and aligning artificial PCCs in field-aligned copolymer PEMs, nanofiber composite PEMs and mesoporous PEMs have set new paradigms for improvement of membrane performances. This perspective profiles the recent development of the channels, from the self-assembled to the artificial, with a particular emphasis on their formation and alignment. It concludes with an outlook on benefits of highly aligned PCCs for fuel cell operation, and gives further direction to develop new PEMs from a practical point of view.

Abstract  A novel immunoassay protocol for simultaneous electrochemical determination of alpha-fetoprotein (AFP), carcinoembryonic (CEA) and streptococcus suis serotype 2 (SS2) was designed. As standard sandwich-type immunoassay format, three primary antibodies (Ab1), anti-CEA and anti-AFP and anti-SS2, were immobilized via protein A (PA) adsorbed by Nafion modified electrodes, and functionalized graphene sheets (GS), containing abundant gold nanoparticles (AuNPs) and carboxyl group, were used to immobilize secondary antibody@redox-probe so as to act as tracer. Concentration of each analyte was quantitatively related to the reduction peak current of corresponding redox-probe in differential pulse voltammetry (DPV) scan. The resulting immunosensor exhibited high selectivity and sensitivity in simultaneous determination of three analytes. The linear range was from 0.016 to 50 ng/mL for AFP with a detection limit of 5.4 pg/mL, 0.010 to 50 ng/mL for CEA with a detection limit of 2.8 pg/mL and 0.012 to 50 ng/mL for SS2 with a detection limit of 4.2 pg/mL (S/N=3).

Abstract  A novel biosensing platform was developed by combining the advantages of electrospun poly(vinyl alcohol) (PVA)/chitosan nanofibers and graphene oxides (GO). Glucose oxidase (GOD) was employed as a model enzyme. By co-electrospinning the solution of PVA, chitosan, GOD and GO, the PVA/chitosan/GOD/GO nanofibers were directly modified on the platinum (Pt) electrode. The UV-vis spectra and the FTIR spectra were used to characterize the GO nanosheets. The morphologies of fabricated electrospun nanofibers were characterized by high resolution scanning electron microscopy. After a thin layer of nafion was modified on the surface of matrix, the as-prepared electrode was used to detect glucose. The electrode exhibited great advantages in high sensitivity, low detection limit and wide linear range. In the meantime, the electrode showed good stability, acceptable reproducibility, and excellent anti-interference capability for ascorbic acid, uric acid, lactose and sucrose. Moreover, the novel biosensor was successfully applied for the glucose determination in human serum samples. The mechanism of efficient biosensing of the nafion/PVA/chitosan/GOD/GO/Pt electrode was analyzed in detail and the results show that it can be due to the synergy effects of electrospun nanofibers and GO nanosheets.

Abstract  Sustaining high-quality respirometry measurements on animals for estimating metabolic rate and fuel use is challenging. I present a general discussion and selected methods for automated measurements spanning over >4 mo with little need for adjustments or maintenance. 1) Lack of compensation for respiratory volume change may cause 6% error in the results on a fasting animal. The Haldane transformation provides the simplest calculation method for both O(2) and CO(2) measurements. 2) Use of Nafion tube dryers configured as countercurrent moisture exchangers provides maintenance-free drying of gases, with typical outlet dew points at -25 to -38°C and no CO(2) adsorption. The accuracy is improved by low dead space, making it feasible to pass gases though the same dryer. 3) A software algorithm employing a triple interpolation technique allows corrections for automated calibrations of O(2) and CO(2) with both zero-reference and span gas. 4) Burning known amounts of 100% ethanol provides total system verification of both O(2) consumption and respiratory quotient. A calculation method to supply instant CO(2) calibration gas from an alcohol burn is presented. 5) Automatic flow switching triggered by low/high O(2) thresholds improves accuracy of measurements and safety for the animals experiencing large ranges of O(2) consumption; this is a special requirement for recording metabolism in small hibernating mammals.