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  • Falk, Magnus, et al. (författare)
  • Biofuel cell as a power source for electronic contact lenses.
  • 2012
  • Ingår i: Biosensors & bioelectronics. - Elsevier. - 1873-4235. ; 37:1, s. 38-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Here we present unequivocal experimental proof that microscale cofactor- and membrane-less, direct electron transfer based enzymatic fuel cells do produce significant amounts of electrical energy in human lachrymal liquid (tears). 100μm diameter gold wires, covered with 17nm gold nanoparticles, were used to fashion three-dimensional nanostructured microelectrodes, which were biomodified with Corynascus thermophilus cellobiose dehydrogenase and Myrothecium verrucaria bilirubin oxidase as anodic and cathodic bioelements, respectively. The following characteristics of miniature glucose/oxygen biodevices operating in human tears were registered: 0.57V open-circuit voltage, about 1μWcm(-2) maximum power density at a cell voltage of 0.5V, and more than 20h operational half-life. Theoretical calculations regarding the maximum recoverable electrical energy can be extracted from the biofuel and the biooxidant, glucose and molecular oxygen, each readily available in human lachrymal liquid, fully support our belief that biofuel cells can be used as electrical power sources for so called smart contact lenses.
  • Ruzgas, Tautgirdas, et al. (författare)
  • Electrochemical characterization and application of azurin-modified gold electrodes for detection of superoxide
  • 2006
  • Ingår i: Biosensors & bioelectronics. - 0956-5663. ; 22:2, s. 213-219
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel biosensor for superoxide radical (O2{radical dot}-) detection based on Pseudomonas aeruginosa azurin immobilized on gold electrode was designed. The rate constant of azurin reduction by O2{radical dot}- was found to be 105 M-1 s-1 in solution and five times lower, i.e., 0.2 × 105 M-1 s-1, for azurin coupled to gold by 3,3′-dithiobis(sulfosuccinimidylpropionate) (DTSSP). The electron transfer rate between the protein and the electrode ranged from 2 to 6 s-1. The sensitivity of this biosensor to O2{radical dot}- was 6.8 × 102 A m-2 M-1. The response to the interference substances, such as uric acid, H2O2, and dimethylsulfoxide was negligible below 10 μM. The electrode was applied in three O2{radical dot}- generating systems: (i) xanthine oxidase (XOD), (ii) potassium superoxide (KO2), and (iii) stimulated neutrophil granulocytes. The latter was compared with luminol-amplified chemiluminescence. The biosensor responded to O2{radical dot}- in all three environments, and the signals were antagonized by superoxide dismutase. © 2006 Elsevier B.V. All rights reserved.
  • Shleev, Sergey, et al. (författare)
  • Simultaneous use of electrochemistry and chemiluminescence to detect reactive oxygen species produced by human neutrophils
  • 2008
  • Ingår i: Cell Biology International. - 1065-6995. ; 32:12, s. 1486-1496
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel approach for the simultaneous optical and electrochemical detection of biologically produced reactive oxygen species has been developed and applied. The set-up consists of a luminol-dependent chemiluminescence assay combined with two amperometric biosensors sensitive to superoxide anion radicals (O-2(center dot-))and hydrogen peroxide (H2O2), respectively. The method permits direct, real-time in vitro determination of both extra-and intracellular O-2(center dot-) and H2O2 produced by human neutrophil granulocytes. The rate of O-2(center dot-) production by stimulated neutrophils was calculated to about 10(-17) mol s(-1) per single cell. With inhibited NADPH oxidase, a distinct extracellular release of H2O2 instead of O-2(center dot-) was obtained from stimulated neutrophils with the rate of about 3 . 10(-18) mol s(-1) per single cell. When the H2O2 release was discontinued, fast H2O2 utilisation was observed. Direct interaction with and possibly attachment of neutrophils to redox protein-modified gold electrodes, resulted in a spontaneous respiratory burst in the population of cells closely associated to the electrode surface. Hence, further stimulation of human neutrophils with a potent receptor agonist (fMLF) did not significantly increase the O-2(center dot-) sensitive amperometric response. By contrast, the H2O2 sensitive biosensor, based on an HRP-modified graphite electrode, was able to reflect the bulk concentration of H2O2, produced by stimulated neutrophils and would be very useful in modestly equipped biomedical research laboratories. In summary, the system would also be appropriate for assessment of several other metabolites in different cell types, and tissues of varying complexity, with only minor electrode modifications.
  • Björklund, Sebastian, et al. (författare)
  • Skin Membrane Electrical Impedance Properties under the Influence of a Varying Water Gradient.
  • 2013
  • Ingår i: Biophysical Journal. - Elsevier. - 0006-3495 .- 1542-0086. ; 104:12, s. 2639-2650
  • Tidskriftsartikel (refereegranskat)abstract
    • The stratum corneum (SC) is an effective permeability barrier. One strategy to increase drug delivery across skin is to increase the hydration. A detailed description of how hydration affects skin permeability requires characterization of both macroscopic and molecular properties and how they respond to hydration. We explore this issue by performing impedance experiments on excised skin membranes in the frequency range 1 Hz to 0.2 MHz under the influence of a varying gradient in water activity (aw). Hydration/dehydration induces reversible changes of membrane resistance and effective capacitance. On average, the membrane resistance is 14 times lower and the effective capacitance is 1.5 times higher when the outermost SC membrane is exposed to hydrating conditions (aw = 0.992), as compared to the case of more dehydrating conditions (aw = 0.826). Molecular insight into the hydration effects on the SC components is provided by natural-abundance (13)C polarization transfer solid-state NMR and x-ray diffraction under similar hydration conditions. Hydration has a significant effect on the dynamics of the keratin filament terminals and increases the interchain spacing of the filaments. The SC lipids are organized into lamellar structures with ∼ 12.6 nm spacing and hexagonal hydrocarbon chain packing with mainly all-trans configuration of the acyl chains, irrespective of hydration state. Subtle changes in the dynamics of the lipids due to mobilization and incorporation of cholesterol and long-chain lipid species into the fluid lipid fraction is suggested to occur upon hydration, which can explain the changes of the impedance response. The results presented here provide information that is useful in explaining the effect of hydration on skin permeability.
  • Coman, Vasile, et al. (författare)
  • A Direct Electron Transfer-Based Glucose/Oxygen Biofuel Cell Operating in Human Serum
  • 2010
  • Ingår i: Fuel Cells. - Wiley-V C H Verlag Gmbh. - 1615-6846. ; 10:1, s. 9-16
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the fabrication and characterisation of the very first direct electron transfer-based glucose/oxygen biofuel cell (BFC) operating in neutral glucose-containing buffer and human serum. Corynascus thermophilus cellobiose dehydrogenase and Myrothecium verrucaria bilirubin oxidase were used as anodic and cathodic bioelements, respectively. The following characteristics of the mediator-, separator- and membrane-less, a priori, non-toxic and simple miniature BFC, was obtained: an open-circuit voltage of 0.62 and 0.58 V, a maximum power density of ca. 3 and 4 mu W cm(-2) at 0.37 and 0.19 V of cell voltage, in phosphate buffer and human serum, respectively.
  • Coman, Vasile, et al. (författare)
  • A membrane-, mediator-, cofactor-less glucose/oxygen biofuel cell.
  • 2008
  • Ingår i: Physical chemistry chemical physics : PCCP. - Royal Society of Chemistry. - 1463-9076. ; 10:40, s. 6093-6096
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the fabrication and characterisation of a non-compartmentalised, mediator and cofactor free glucose-oxygen biofuel cell based on adsorbed enzymes exhibiting direct bioelectrocatalysis, viz. cellobiose dehydrogenase from Dichomera saubinetii and laccase from Trametes hirsuta as the anodic and cathodic bioelements, respectively, with the following characteristics: an open-circuit voltage of 0.73 V; a maximum power density of 5 muW cm(-2) at 0.5 V of the cell voltage and an estimated half-life of >38 h in air-saturated 0.1 M citrate-phosphate buffer, pH 4.5 containing 5 mM glucose.
  • Fagerström, Anton, et al. (författare)
  • Effects of surfactants and thermodynamic activity of model active ingredient on transport over plant leaf cuticle
  • 2013
  • Ingår i: Colloids and Surfaces B: Biointerfaces. - Elsevier. - 0927-7765.
  • Tidskriftsartikel (refereegranskat)abstract
    • The main objective of this study was to investigate the mechanism of molecular transport across the cuticle of Clivia leaves. In vitro diffusion methodology was used to investigate the transport of a systemic fungicide, tebuconazole, over a model silicone membrane, enzymatically isolated cuticle membranes, and dermatomed leaves. It was shown that dermatomed leaves may replace enzymatically isolated cuticles. Furthermore, the effects of two surfactants, C10EO7 and C8G1.6, on the fungicide transport were investigated. Tebuconazole cuticle permeation was described using Fick's first law of diffusion, expressed by the thermodynamic activity of the solute in the membrane. A new method for calculation of diffusion coefficients in the membrane is proposed. To access the thermodynamic activity of the fungicide in the membranes, sorption isotherms of tebuconazole in the membrane materials studied were recorded. The thermodynamic activity of the fungicide in aqueous solutions was calculated from solubility data. For that purpose, the effect of surfactants on tebuconazole solubility was studied. The results show that addition of surfactants allows for higher concentrations of tebuconazole available for penetration. Nonetheless, at a fixed fungicide thermodynamic activity, all formulations produced the same flux over the silicone membrane independently on the fungicide concentration. This shows that the driving force across non-responding membranes is the gradient of thermodynamic activity, rather than the gradient of the fungicide concentration. In case of leaves, surfactants induced the same quantitative increase in both flux and diffusion coefficient of solute in the cuticle, while the cuticle-water partition coefficient was unaffected.
  • Haberska, Karolina, et al. (författare)
  • Activity of lactoperoxidase when adsorbed on protein layers
  • 2008
  • Ingår i: Talanta. - Elsevier. - 0039-9140. ; 76:5, s. 1159-1164
  • Tidskriftsartikel (refereegranskat)abstract
    • Lactoperoxidase (LPO) is an enzyme, which is used as an antimicrobial agent in a number of applications, e.g., food technology. In the majority of applications LPO is added to a homogeneous product phase or immobilised on product surface. In the latter case, however, the measurements of LPO activity are seldom reported. In this paperwe have assessed LPO enzymatic activity on bare and protein modified gold surfaces by means of electrochemistry. It was found that LPO rapidly adsorbs to bare gold surfaces resulting in an amount of LPO adsorbed of 2.9mg/m2. A lower amount of adsorbed LPO is obtained if the gold surface is exposed to bovine serum albumin, bovine or human mucin prior to LPO adsorption. The enzymatic activity of the adsorbed enzyme is in general preserved at the experimental conditions and varies only moderately when comparing bare gold and gold surface pretreated with the selected proteins. The measurement of LPO specific activity, however, indicate that it is about 1.5 times higher if LPO is adsorbed on gold surfaces containing a small amount of preadsorbed mucin in comparison to the LPO directly adsorbed on bare gold.
  • Haberska, Karolina, et al. (författare)
  • Polymer multilayer film formation studied by in situ ellipsometry and electrochemistry
  • 2009
  • Ingår i: Bioelectrochemistry. - Elsevier B.V..
  • Tidskriftsartikel (refereegranskat)abstract
    • Polyelectrolyte multilayer films adsorbed on gold surfaces were studied by combined ellipsometric and electrochemical methods. Multilayers were composed of “synthetic” (poly(4-styrenesulfonic acid) ammonium salt (PSS) and poly(allylamine hydrochloride) (PAH) (PSS/PAH)) and “semi-natural” (carboxymethyl cellulose (CMC) and chitosan (CHI) (CMC/CHI)) polyelectrolytes. It was found that only PSS/PAH Layer-by-Layer (LbL) assembled structures result in dense surface confined films that limit permeability of small molecules, such as ferri-/ferrocyanide. The PSS/PAH assemblies can be envisaged as films with pinholes, through which small molecules diffuse. During the LbL deposition process of these films a number of pinholes quickly decay. A representative pinhole diameter was found to be approximately 20 μm, which determines the diffusion of small molecules through LbL films, and yet remains constant when the film consists of a few LbL assembled polyelectrolyte bilayers. CMC/CHI LbL assemblies at gold electrode surfaces give very low density films, which do not limit the diffusion of ferri-/ferrocyanide between the surface of the electrode and the solution.
  • Heiskanen, Arto, et al. (författare)
  • Mediator-assisted simultaneous probing of cytosolic and mitochondrial redox activity in living cells.
  • 2009
  • Ingår i: Analytical biochemistry. - Elsevier Inc. - 1096-0309. ; 384:1, s. 11-19
  • Tidskriftsartikel (refereegranskat)abstract
    • This work describes an electron transfer mediator-assisted amperometric flow injection method for assessing redox enzyme activity in different subcellular compartments of the phosphoglucose isomerase deletion mutant strain of Saccharomyces cerevisiae, EBY44. The method is demonstrated using the ferricyanide-menadione double mediator system to study the effect of dicoumarol, an inhibitor of cytosolic and mitochondrial oxidoreductases and an uncoupler of the electron transport chain. Evaluation of the role of NAD(P)H-producing pathways in mediating biological effects is facilitated by introducing either fructose or glucose as the carbon source, yielding either NADH or NADPH through the glycolytic or pentose phosphate pathway, respectively. Respiratory noncompetent cells show greater inhibition of cytosolic menadione-reducing enzymes when NADH rather than NADPH is produced. Spectrophotometric in vitro assays show no difference between the cofactors. Respiratory competent cells show cytosolic inhibition only when NADPH is produced, whereas production of NADH reveals uncoupling at low dicoumarol concentrations and inhibition of complexes III and IV at higher concentrations. Spectrophotometric assays only indicate the presence of cytosolic inhibition regardless of the reduced cofactor used. This article shows the applicability of the amperometric method and emphasizes the significance of determining biological effects of chemicals in living cells.
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