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Sökning: swepub > Malmö universitet > Engelska > Ruzgas Tautgirdas

  • Resultat 1-10 av 57
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  • Shleev, Sergey, 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. - Cell Press. - 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.
  • Björklund, Sebastian, et al. (författare)
  • The effects of polar excipients transcutol and dexpanthenol on molecular mobility, permeability, and electrical impedance of the skin barrier
  • 2016
  • Ingår i: Journal of Colloid and Interface Science. - Elsevier. - 0021-9797. ; 479, s. 207-220
  • Tidskriftsartikel (refereegranskat)abstract
    • In the development of transdermal and topical products it is important to understand how formulation ingredients interact with the molecular components of the upper layer of the skin, the stratum corneum (SC), and thereby influence its macroscopic barrier properties. The aim here was to investigate the effect of two commonly used excipients, transcutol and dexpanthenol, on the molecular as well as the macroscopic properties of the skin membrane. Polarization transfer solid-state NMR methods were combined with steady-state flux and impedance spectroscopy measurements to investigate how these common excipients influence the molecular components of SC and its barrier function at strictly controlled hydration conditions in vitro with excised porcine skin. The NMR results provide completely new molecular insight into how transcutol and dexpanthenol affect specific molecular segments of both SC lipids and proteins. The presence of transcutol or dexpanthenol in the formulation at fixed water activity results in increased effective skin permeability of the model drug metronidazole. Finally, impedance spectroscopy data show clear changes of the effective skin capacitance after treatment with transcutol or dexpanthenol. Based on the complementary data, we are able to draw direct links between effects on the molecular properties and on the macroscopic barrier function of the skin barrier under treatment with formulations containing transcutol or dexpanthenol.
  • Coman, Vasile, et al. (författare)
  • A membrane-, mediator-, cofactor-less glucose/oxygen biofuel cell.
  • 2008
  • Ingår i: Physical Chemistry Chemical Physics. - Royal Society of Chemistry. - 1463-9084. ; 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.
  • 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.
  • Falk, Magnus, et al. (författare)
  • Self-powered wireless carbohydrate/oxygen sensitive biodevice based on radio signal transmission.
  • 2014
  • Ingår i: PLoS ONE. - Public Library of Science. - 1932-6203. ; 9:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 µA and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply.
  • Gari, Hala, et al. (författare)
  • Amperometric In Vitro Monitoring of Penetration through Skin Membrane
  • 2015
  • Ingår i: Electroanalysis. - John Wiley & Sons. - 1040-0397. ; 27:1, s. 111-117
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to demonstrate that penetration of quercetin, hydrogen peroxide and ascorbic acid through skin membranes can be monitored amperometrically. Skin membrane was fixed on the top of chemically modified electrodes and penetration of the appropriate compound was registered as electrode current. The methodology allows the study of penetration from solution as well as from pharmaceutical creams. From real-time measurements of electrode current, fluxes and diffusion coefficients of mentioned compounds in skin membranes have been estimated.
  • Haberska, Karolina, et al. (författare)
  • Activity of lactoperoxidase when adsorbed on protein layers
  • 2008
  • Ingår i: Talanta. - Elsevier. - 1873-3573. ; 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. - 1878-562X. ; 76, s. 153-161
  • 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.
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