| 1. |
- Aghbolagh, Mahdi Shahmohammadi, et al.
(författare)
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Aspects on mediated glucose oxidation at a supported cubic phase
- 2017
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 118, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase. The system was investigated with cyclic voltammetry at different scan rates and the temperature was varied between 15 degrees C and 30 degrees C. The diffusion coefficient of the mediator and also the film resistance was estimated showing a large decrease in the mass-transport properties as the temperature was decreased. The current from mediated oxidation of glucose at the electrode surface increased with decreasing film thickness. The transport of the mediator in the cubic phase was the rate-limiting step in the overall reaction, where the oxidation of glucose took place at the outer surface of the cubic phase.
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| 2. |
- Aghoutane, Youssra, et al.
(författare)
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Development of a molecularly imprinted polymer electrochemical sensor and its application for sensitive detection and determination of malathion in olive fruits and oils
- 2020
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 132
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Tidskriftsartikel (refereegranskat)abstract
- Malathion (MAL) is an organophosphorus (OP) insecticide. It is a cholinesterase inhibitor, 15 which can pose serious health and environmental problems. In this study, a sensitive and 16 selective molecular imprinted polymer (MIP) based on screen-printed gold electrodes (Au-17 SPE) for MAL detection in olive oils and fruits, was devised. The MIP sensor was prepared 18 using acrylamide as the functional monomer and MAL as the template. Subsequently, the 19 morphology of the electrode surface was studied by scanning electron microscopy (SEM) and 20 atomic force microscopy (AFM). The electrochemical characterization of the developed MIP 21 sensor was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), 22 and electrochemical impedance spectroscopy (EIS) techniques. The operational repeatability 23 and stability of the sensor were studied. It was found to have a dynamic concentration range 24 of (0.1 pg mL-1-1000 pg mL-1) and a low limit of detection (LOD) of 0.06 pg mL-1. 25 Furthermore, the sensor was employed to determine MAL content in olive oil with a recovery 26 rate of 87.9% and a relative standard deviation of 8%. It was successfully applied for MAL 27 determination in real samples and promise to open new opportunities for the detection of OP 28 pesticides residues in various food products, as well as in environmental applications.
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| 3. |
- Agmo Hernández, Víctor, et al.
(författare)
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The lipid composition determines the kinetics of adhesion and spreading of liposomes on mercury electrodes
- 2008
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 74:1, s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- The dependence of membrane properties on their composition was studied by following the adhesion and spreading of unilamellar and multilamellar liposomes on static mercury electrodes with the help of chronoamperometry. The analysis of the peak-shaped signals allows determining the kinetic parameters of the three-step adhesion-spreading process. The presence of cholesterol in the membrane stabilizes the bilayer in the liquid-crystal line phase, and destabilizes the gel phase. The kinetic parameters also show the effect of superlattice formation in the DMPC-cholesterol system. The detergent triton X-100 is only incorporated in the liquid-crystalline DMPC membranes, and it is expelled to the solution when the membrane is transformed to the gel phase. In the liquid-crystalline membrane, it enhances the adhesion-spreading of liposomes on mercury. The lyric peptides mastoparan X and melittin affect the adhesion-spreading in a similar manner. For the rupture-spreading step, their effect is explained by pore formation. The results obtained with lecithins of different length suggest that the bilayer opening process has much in common with flip-flop translocations. For this process the activation energies were found to be independent of the chain length of the lecithin molecules, while the preexponential factor in the Arthenius equation decreases drastically for longer chains.
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| 4. |
- Al-Khafaji, Alia Hussain, et al.
(författare)
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Germination and stress tolerance of oats treated with pulsed electric field at different phases of seedling growth
- 2024
-
Ingår i: Bioelectrochemistry. - 1567-5394 .- 1878-562X. ; 158
-
Tidskriftsartikel (refereegranskat)abstract
- This study explores the impact of pulsed electric field (PEF) application on oat seedling growth and stress tolerance. PEF treatment (99 monopolar, rectangular pulses lasting 10 µs each, with a frequency of 13 Hz and a nominal electric field strength of 2250 V/cm) was applied at two growth stages: (i) when the seedlings had 0.2 cm roots emerging from the kernel, and (ii) when they had a 0.4 cm shoot emerging from the kernel. Post-treatment, the seedlings were hydroponically grown for 8 days. To induce stress, the hydroponic medium was augmented with PEG (15 %) to induce drought stress and NaCl (150 mM) to induce salinity stress. Results demonstrate that applying PEF improved the growth of the root and shoot of oat seedlings. This effect was more pronounced when applied to more developed seedlings. When PEF was applied during the later stage of germination, seedlings exposed to salinity stress showed enhanced shoot growth compared to the control. Under the studied conditions, the application of PEF had no impact on the growth of seedlings under drought stress.
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| 5. |
- Aleksejeva, Olga, et al.
(författare)
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Autotolerant ceruloplasmin based biocathodes for implanted biological power sources
- 2021
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- High-performance autotolerant bioelectrodes should be ideally suited to design implantable bioelectronic devices. Because of its high redox potential and ability to reduce oxygen directly to water, human ceruloplasmin, HCp, the only blue multicopper oxidase present in human plasma, appears to be the ultimate biocatalyst for oxygen biosensors and also biocathodes in biological power sources. In comparison to fungal and plant blue multicopper oxidases, e.g. Myrothecium verrucaria bilirubin oxidase and Rhus vernicifera laccase, respectively, the inflammatory response to HCp in human blood is significantly reduced. Partial purification of HCp allowed to preserve the native conformation of the enzyme and its biocatalytic activity. Therefore, electrochemical studies were carried out with the partially purified enzyme immobilised on nanostructured graphite electrodes at physiological pH and temperature. Amperometric investigations revealed low reductive current densities, i.e. about 1.65 µA cm−2 in oxygenated electrolyte and in the absence of any mediator, demonstrating nevertheless direct electron transfer based O2 bioelectroreduction by HCp for the first time. The reductive current density obtained in the mediated system was about 12 µA cm−2. Even though the inflammatory response of HCp is diminished in human blood, inadequate bioelectrocatalytic performance hinders its use as a cathodic bioelement in a biofuel cell.
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| 6. |
- Andoralov, Victor, et al.
(författare)
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Octaheme nitrite reductase : The mechanism of intramolecular electron transfer and kinetics of nitrite bioelectroreduction.
- 2021
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- Detailed impedance and voltammetric studies of hexameric octaheme nitrite reductase immobilized on carbon-based nanomaterials, specifically nanotubes and nanoparticles, were performed. Well-pronounced bioelectrocatalytic reduction of nitrite on enzyme-modified electrodes was obtained. Analysis of the impedance data indicated the absence of long-lived intermediates involved in the nitrite reduction. Cyclic voltammograms of biomodified electrodes had a bi-sigmoidal shape, which pointed to the presence of two enzyme orientations on carbon supports. The maximum (limiting) catalytic currents were determined and, by applying the correction by the mixed kinetics equation, the Tafel dependences were plotted for each catalytic wave/each enzyme orientation. Finally, two schemes for the rate-limiting processes during bioelectrocatalysis were proposed, viz. for low- and high-potential orientations.
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| 7. |
- Baranowska, Irena, et al.
(författare)
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Determination of selected drugs in human urine by differential pulse voltammetry technique
- 2008
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 73:1
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Tidskriftsartikel (refereegranskat)abstract
- A new, simple and selective differential pulse voltammetry (DPV) method for the simultaneous determination of selected drugs in model solutions and spiked human urine samples with prior extraction was developed and validated. The objects of analysis were paracetamol, furosemide, dipyrone, cefazolin and dexamethasone belonging to four different therapeutic groups (antibiotics, analgesic, demulcent and diuretic). Analytical methods for the preparation of urine samples for voltammetric analysis (liquid-liquid extraction - LLE and solid-phase extraction - SPE) were worked out and optimized. Hanging mercury drop electrode (HMDE) and graphite electrode were used as working electrodes. Reference electrode was Ag vertical bar AgCl vertical bar KCI(sat.), whereas auxiliary electrode - platinum electrode. The optimal conditions for quantitative determination were obtained in a Britton-Robinson (BR) buffer at pH 2.4. Quantification was performed by means of calibration curve and standard addition methods. The calibration curves of analysed drugs are linear within the range of concentration: 6.61-66.10, 6.05-54.42, 6.00-65.00, 4.20-33.58 and 0.51-3.06 mu M for paracetamol, furosemide, dipyrone, cefazolin and dexamethasone, respectively. The levels of analysed compounds in human urine can be successfully determined using this developed method with no matrix effect. (C) 2008 Elsevier B.V. All rights reserved.
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| 8. |
- Deenin, Wanwisa, et al.
(författare)
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Electrochemical lateral-flow device for rapid COVID-19 antigen-diagnostic testing
- 2023
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 152
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Tidskriftsartikel (refereegranskat)abstract
- Antigen test kits (ATK) are extensively utilized for screening and diagnosing COVID-19 because they are easy to operate. However, ATKs exhibit poor sensitivity and cannot detect low concentrations of SARS-CoV-2. Herein, we present a new, highly sensitive, and selective device obtained by combining the principle of ATKs with elec-trochemical detection for COVID-19 diagnosis, which can be quantitatively assessed using a smartphone. An electrochemical test strip (E-test strip) was constructed by attaching a screen-printed electrode inside a lateral -flow device to exploit the remarkable binding affinity of SARS-CoV-2 antigen to ACE2. The ferrocene carboxylic acid attached to SARS-CoV-2 antibody acts as an electroactive species when it binds to SARS-CoV-2 antigen in the sample before it flows continuously to the ACE2-immobilization region on the electrode. Electrochemical-assay signal intensity on smartphones increased proportionally to the concentration of SARS-CoV-2 antigen (LOD = 2.98 pg/mL, under 12 min). Additionally, the application of the single-step E-test strip for COVID-19 screening was demonstrated using nasopharyngeal samples, and the results were consistent with those obtained using the gold standard (RT-PCR). Therefore, the sensor demonstrated excellent performance in assessing and screening COVID-19, and it can be used professionally to accurately verify diagnostic data while remaining rapid, simple, and inexpensive.
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| 9. |
- Di Bari, Chiara, et al.
(författare)
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Laccase-modified gold nanorods for electrocatalytic reduction of oxygen
- 2016
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 107, s. 30-36
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Tidskriftsartikel (refereegranskat)abstract
- The multicopper oxidase Trametes hirsuta laccase (ThLc) served as a bioelectrocatalyst on nanostructured cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-d. graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen redn. were as high as 0.5 mA/cm2 and 0.7 mA/cm2, which were recorded under direct and mediated electron transfer regimes, resp. The exptl. data were fitted to math. models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rate-liming stage. The electrochem. measurement hints a wider population of non-optimally wired laccases than previously reported for 5-8 nm size Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets.
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| 10. |
- Dymek, Katarzyna, et al.
(författare)
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Investigation of the metabolic consequences of impregnating spinach leaves with trehalose and applying a pulsed electric field.
- 2016
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 112, s. 153-157
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Tidskriftsartikel (refereegranskat)abstract
- The impregnation of leafy vegetables with cryoprotectants using a combination of vacuum impregnation (VI) and pulsed electric fields (PEF) has been proposed by our research group as a method of improving their freezing tolerance and consequently their general quality after thawing. In this study, we have investigated the metabolic consequences of the combination of these unit operations on spinach. The vacuum impregnated spinach leaves showed a drastic decrease in the porosity of the extracellular space. However, at maximum weight gain, randomly located air pockets remained, which may account for oxygen-consuming pathways in the cells being active after VI. The metabolic activity of the impregnated leaves showed a drastic increase that was further enhanced by the application of PEF to the impregnated tissue. Impregnating the leaves with trehalose by VI led to a significant accumulation of trehalose-6-phosphate (T6P), however, this was not further enhanced by PEF. It is suggested that the accumulation of T6P in the leaves may increase metabolic activity, and increase tissue resistance to abiotic stress.
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| 11. |
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| 12. |
- Ferancova, A, et al.
(författare)
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Association interaction and voltammetric determination of 1-aminopyrene and 1-hydroxypyrene at cyclodextrin and DNA based electrochemical sensors
- 2005
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 67:2, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was voltammetric determination of 1-aminopyrene and 1-hydroxypyrene using carbon paste electrodes modified with cyclodextrin derivatives and double stranded deoxyribonucleic acid (dsDNA). The detection schemes based on a preconcentration and differential pulse voltammetric (DPV) determination at beta-cyclodextrin and gamma-cyclodextrin modified carbon paste electrode (beta-CD/CPE, gamma CD/CPE), neutral beta-cyclodextrin polymer and carboxymethyl-beta-cyclodextrin polymer modified screen-printed electrode (beta-CDP/SPE, beta-CDPA/SPE) and dsDNA modified screen-printed electrode (DNA/SPE) are proposed for the trace determination of studied analytes within the concentration range from 2 x 10(-8) to 4 x 10(-7) mol dm(-3) and from 2 x 10(-7) to 4 x 10(-6) mol dm(-3) with the limits of quantification down to 10-8 mol dm-3. Depending on pH, 1-aminopyrene interacts with both surface attached CD and DNA by electrostatic bonds and supramolecular complexation while 1-hydroxypyrene associates with the CD hosts via complexation. The 1-aminopyrene interaction with dsDNA was confirmed by fluorimetric measurements in the solution phase using a competing DNA-TO-PRO-3 dye complex. In addition, the effect of temperature on this association was investigated using an electrically heated DNA-modified carbon paste electrode (DNA/CPE). (c) 2005 Elsevier B.V. All rights reserved.
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| 13. |
- Ferapontova, Elena, et al.
(författare)
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Direct electrochemistry of heme multicofactor-containing enzymes on alkanethiol-modified gold electrodes
- 2005
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 66:1-2, s. 55-63
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Tidskriftsartikel (refereegranskat)abstract
- Direct electrochemistry of heme multicofactor-containing enzymes, e.g., microbial theophylline oxidase (ThOx) and D-fructose dehydrogenase (FDH) from Gluconobacter industrius was studied on alkanethiol-modified gold electrodes and was compared with that of some previously studied complex heme enzymes, specifically, cellobiose dehydrogenase (CDH) and sulphite oxidase (SOx). The formal redox potentials for enzymes in direct electronic communication varied for ThOx from -112 to -101 mV (vs. Ag vertical bar AgCl), at pH 7.0, and for FDH from - 158 to -89 mV, at pH 5.0 and pH 4.0, respectively, on differently charged alkanethiol layers. Direct and mediated by cytochrome c electrochemistry of FDH correlated with the existence of two active centres in the protein structure, i.e., the heme and the pyrroloquinoline quinone (PQQ) prosthetic groups. The effect of the alkanethiols of different polarity and charge on the surface properties of the g-old electrodes necessary for adsorption and orientation of ThOx, FDH, CDH and SOx, favourable for the efficient electrode-enzyme electron transfer reaction, is discussed. (c) 2004 Elsevier B.V. All rights reserved.
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| 14. |
- Ferapontova, Elena, et al.
(författare)
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Spectroelectrochemical study of heme- and molybdopterin cofactor-containing chicken liver sulphite oxidase
- 2004
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 63:1-2, s. 49-53
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Tidskriftsartikel (refereegranskat)abstract
- Electron transfer (ET) in sulphite oxidase (SOx), a heme- and molybdopterin cofactor-containing enzyme, was studied spectroelectrochemically using capillary gold electrode modified with aldrithiol. Direct electron exchange between SOx and the surface of modified gold was observed, with a formal potential of -115 mV vs. AgAgCl, KClsat at pH 7.0. This value agreed well with that previously reported for redox transformation of the heme domain of SOx. However, no bioelectrocatalysis of sulphite oxidation was observed in phosphate buffer solutions. This fact evidently correlated with known inhibition of intramolecular ET in SOx by the presence of bivalent inorganic anions. After changing to a Tris buffer solution, spectra variations and cyclic voltammetry data designated direct ET-based bioelectrocatalysis of sulphite oxidation, upon addition of sulphite. Thus, the bioelectrocatalytic 2e(-) oxidation of sulphite catalysed by SOx due to direct ET exchange with the electrode was attained at aldrithiol-modified gold electrodes and shown to depend essentially on the nature of the buffer solution. (C) 2004 Elsevier B.V. All rights reserved.
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| 15. |
- Ghosh, Tanushree, et al.
(författare)
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A novel third generation uric acid biosensor using uricase electro-activated with ferrocene on a Nafion coated glassy carbon electrode
- 2015
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 102
-
Tidskriftsartikel (refereegranskat)abstract
- A new uric acid biosensor was constructed using ferrocene (Fc) induced electro-activated uricase (UOx) deposited within Nation (Naf) on glassy carbon electrode (GCE). Electro-activation of UOx was successfully achieved by cyclic voltammetry through the electrostatic interaction of Fc with Trp residues within the hydrophobic pockets in UOx. The Naf/UOx/Fc composite was characterised by AFM, FTIR and EDX to ensure proper immobilisation. The interaction of Fc with the enzyme was analysed by Trp fluorescence spectroscopy and the alpha-helicity of the protein was measured by CD spectropolarimetry. The charge transfer resistance (R-ct), calculated from electrochemical impedance spectroscopy, for the modified sensor was lowered (1.39 k Omega) and the enzyme efficiency was enhanced by more than two fold as a result of Fc incorporation. Cyclic voltammetty, differential pulse voltammetty and amperometry all demonstrated the excellent response of the Naf/UOx/Fc/GCE biosensor to uric acid. The sensor system generated a linear response over a range of 500 nM to 600 mu M UA, with a sensitivity and limit of detection of 1.78 mu A mu M-1 and 230 nM, respectively. The heterogeneous rate constant (k(s)) for UA oxidation was much higher for Naf/UOx/Fc/GCE (1.0 x 10(-4) cm s(-1)) than for Naf/UOx/GCE (8.2 x 10(-5) cm s(-1)). Real samples, i.e. human blood, were tested for serum UA and the sensor yielded accurate results at a 95% confidence limit. (C) 2014 Elsevier B.V. All rights reserved.
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| 16. |
- Haberska, Karolina, et al.
(författare)
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Direct electron transfer reactions between human ceruloplasmin and electrodes.
- 2009
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76, s. 34-41
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to find conditions favouring bioelectrocatalytic reduction of oxygen by surface-immobilised human ceruloplasmin (Cp), direct electron transfer (DET) reactions between Cp and an extended range of surfaces were considered. Exploiting advances in surface nanotechnology, bare and carbon-nanotube-modified spectrographic graphite electrodes as well as bare, thiol- and gold-nanoparticle-modified gold electrodes were considered, and ellipsometry provided clues as to the amount and form of adsorbed Cp. DET was studied under different conditions by cyclic voltammetry and chronoamperometry. Two Faradaic processes with midpoint potentials of about 400 mV and 700 mV vs. NHE, corresponding to the redox transformation of copper sites of Cp, were clearly observed. In spite of the significant amount of Cp adsorbed on the electrode surfaces, as well as the quite fast DET reactions between the redox enzyme and electrodes, bioelectrocatalytic reduction of oxygen by immobilised Cp was never registered. The bioelectrocatalytic inertness of this complex multi-functional redox enzyme interacting with a variety of surfaces might be associated with a very complex mechanism of intramolecular electron transfer involving a kinetic trapping behaviour.
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| 17. |
- Haberska, Karolina, et al.
(författare)
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Polymer multilayer film formation studied by in situ ellipsometry and electrochemistry
- 2009
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 76, s. 153-161
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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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| 18. |
- Hasan, Kamrul, et al.
(författare)
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Electrochemical communication between heterotrophically grown Rhodobacter capsulatus with electrodes mediated by an osmium redox polymer.
- 2013
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 93:Online 15 June 2012, s. 30-36
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Tidskriftsartikel (refereegranskat)abstract
- The metabolically versatile purple bacteria Rhodobacter capsulatus was investigated to check its possible applicability in biofuel cells and electrochemical microbial biosensors. The wild type strain ATCC 17015 and mutant strain 37b4 lacking the lipopolysaccharide capsule was compared for their ability to communicate with electrodes modified with an osmium redox polymer. In this work, aerobic heterotrophically grown R. capsulatus were used to screen for efficient cell-electrode communication for later implementation using photoheterotrophically grown bacteria. The bacterial cells embedded in the osmium polymer matrix demonstrated efficient electrical "wiring" with the electrodes and were able to generate a noticeable current with succinate as substrate. Interestingly, at 2mM succinate the wild type strain showed much better bioelectrocatalytic current generation (4.25μA/cm(2)) than the strain lacking capsule (1.55μA/cm(2)). The wild type strain also exhibited a stable current response for longer time, demonstrating that the bacterial lipopolysaccharide in fact enhances the stability of the polymer matrix layer of the modified electrode. Control experiments with R. capsulatus without any mediator did not show any current irrespective of the capsule presence. This demonstrates that development of photosensors and other light driven bioelectrochemical devices could be feasible using R. capsulatus and will be at focus for future studies.
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| 19. |
- Hernandez, Victor Agmo, et al.
(författare)
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The adhesion and spreading of thrombocyte vesicles on electrode surfaces
- 2008
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 74, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of thrombocyte vesicles with the surface of metal electrodes, i.e., mercury, gold and gold electrodes modified with self assembled monolayers (SAM), was studied with the help of chronoamperometry, atomic force microscopy, and quartz crystal microbalance measurements. The experimental results show that the interaction of the thrombocyte vesicles with the surface of the electrodes depends on the hydrophobicity of the latter: whereas on very hydrophobic surfaces (mercury and gold functionalized with SAM) the thrombocyte vesicles disintegrate and form a monolayer of lipids. on the less hydrophobic gold surface a bilayer is formed. The chronoamperometric measurements indicate the possibility of future applications to probe membrane properties of thrombocytes. (C) 2008 Elsevier B.V. All rights reserved.
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| 20. |
- Isik, Sonnur, et al.
(författare)
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Simultaneous detection of L-glutamate and nitric oxide from adherently growing cells at known distance using disk shaped dual electrodes
- 2007
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 70:1, s. 173-179
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Tidskriftsartikel (refereegranskat)abstract
- An ex vivo system for simultaneous detection of nitric oxide (NO) and L-glutamate using integrated dual 250 gin platinum disk electrodes modified individually with suitable sensing chemistries has been developed. One of the sensors was coated with an electrocatalytic layer of Ni tetrasulfonate phthalocyanine tetrasodium salt (Ni-TSPe) covered by second layer of Nation, which stabilises on the one hand the primary oxidation product NO+ and prevents interferences from negatively charged compounds such as NO2-. For glutamate determination, the second electrode was modified with a crosslinked redox hydrogel consisting of Os complex modified poly(vinylimidazol), glutamate oxidase and peroxidase. A manual x-y-z micromanipulator on top of an inverted optical microscope was used to position the dual electrode sensor at a defined distance of 5 mu m from a cell population under visual control. C6 glioma cells were stimulated simultaneously with bradykinin or VEGF to release NO while KCl was used to invoke glutamate release. For evaluation of the glutamate sensors, in some experiments HN10 cells were used. To investigate the sensitivity and reliability of the system, several drugs were applied to the cells, e.g. Ca2+-channel inhibitors for testing Ca2+-dependence of the release of NO and glutamate, rotenone for inducing oxidative stress and glutamate antagonists for analysing glutamate release. With these drugs the NO and glutamate release was modulated in a similar way then expected from previously described systems or even in-vivo measurements. We therefore conclude that our system is suitable to analyse stress-induced mechanisms in cell lines. (c) 2006 Elsevier B.V All rights reserved.
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| 21. |
- Kizling, Michal, et al.
(författare)
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Bioelectrodes based on pseudocapacitive cellulose/polypyrrole composite improve performance of biofuel cell
- 2016
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 112, s. 184-190
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Tidskriftsartikel (refereegranskat)abstract
- Enzymatic electrodes with high internal capacitance, based on cellulose/polypyrrole composite were optimized and utilized to design improved enzymatic fuel cell. Fructose dehydrogenase Gluconobacter sp. specifically adsorbed on the cellulose/polypyrrole matrix and electrophoretically immobilized and electrochemically entrapped Laccase Trametes versicolor, were used as the anode and cathode bioelectrocatalysts, respectively. The cellulose/polypyrrole composite film exhibited pseudocapacitive properties under mild pH conditions. Following modification with carboxylic groups the composite material enabled highly efficient adsorption of enzyme and provided good electrical contact between the enzymatic active sites and the electrode surface. The modified cellulose/polypyrrole composite based electrode was used for the anode leading to mediatorless fructose oxidation giving large catalytic current density, 12.8 mA cm(-2). Laccase and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) as the mediator entrapped in the cellulose/polypyrrole composite film generated dioxygen reduction current density of 2 mA cm(-2). Application of pseudocapacitive matrix and decreasing the distance between electrodes to 1 mm lead to improvement of the biofuel cell power output and its regeneration ability. The power of the cell was found to increase by introduction of a preconditioning step during which the cell was kept at open circuit voltage under fuel flow. After 24 h of preconditioning the matrix was recharged and the device output reached the power, 2.1 mW cm(-2) and OCV, 0.59 V.
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| 22. |
- Kizling, Michal, et al.
(författare)
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Biosupercapacitors for powering oxygen sensing devices
- 2015
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 106, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- A biofuel cell comprising electrodes based on supercapacitive materials - carbon nanotubes and nanocellulose/polypyrrole composite was utilized to power an oxygen biosensor. Laccase Trametes versicolor, immobilized on naphthylated multi walled carbon nanotubes, and fructose dehydrogenase, adsorbed on a porous polypyrrole matrix, were used as the cathode and anode bioelectrocatalysts, respectively. The nanomaterials employed as the supports for the enzymes increased the surface area of the electrodes and provide direct contact with the active sites of the enzymes. The anode modified with the conducting polymer layer exhibited significant pseudocapacitive properties providing superior performance also in the high energy mode, e.g., when switching on/off the powered device. Three air-fructose biofuel cells connected in a series converted chemical energy into electrical giving 2 mW power and open circuit potential of 2 V. The biofuel cell system was tested under various externally applied resistances and used as a powering unit for a laboratory designed two-electrode minipotentiostat and a laccase based sensor for oxygen sensing. Best results in terms of long time measurement of oxygen levels were obtained in the pulse mode -45 s for measurement and 15 min for self-recharging of the powering unit.
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| 23. |
- Kostesha, Natalie, et al.
(författare)
-
Real-time detection of cofactor availability in genetically modified living Saccharomyces cerevisiae cells - Simultaneous probing of different geno- and phenotypes.
- 2009
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76, s. 180-188
-
Tidskriftsartikel (refereegranskat)abstract
- This work describes a mediated amperometric method for simultaneous real-time probing of the NAD(P)H availability in two different phenotypes, fermentative and respiratory, of the phosphoglucose isomerase deletion mutant strain of S. cerevisiae, EBY44 [ENY.WA-1A pgi1-1D::URA3], and its parental strain, ENY.WA-1A. The developed method is based on multichannel detection using microelectrode arrays. Its versatility was demonstrated by using four microelectrode arrays for simultaneously monitoring the NAD(P)H availability of both geno- and phenotypes under the influence of two different carbon sources, glucose and fructose, as well as the cytosolic and mitochondrial inhibitor and uncoupler, dicoumarol. The obtained results indicate that the method is capable of accurately and reproducibly (overall relative standard error of mean 3.2%) mapping the real-time responses of the cells with different genotype-phenotype combinations. The ENY.WA cells showed the same response to glucose and fructose when dicoumarol was used; fermentative cells indicated the presence of cytosolic inhibition and respiratory cells a net effect of mitochondrial uncoupling. EBY44 cells showed cytosolic inhibition with the exception of respiratory cells when fructose was used as carbon source.
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| 24. |
- Kovacs, Gabor, et al.
(författare)
-
Graphite electrodes modified with Neurospora crassa cellobiose dehydrogenase: Comparative electrochemical characterization under direct and mediated electron transfer
- 2012
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 88, s. 84-91
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochemical characterization of a class II cellobiose dehydrogenase (CDH), from the ascomycete fungus Neurospora crassa. adsorbed on graphite (G), was performed in regard to direct (DET) and mediated electron transfer (MET). The effects of the applied potential, mediator (1,4 benzoquinone) concentration and flow carrier pH on the amperometric response of the G/CDH modified electrodes were investigated under flow conditions. From the calibration curves, recorded at two pH values (5.2 and 7.0) for nine different sugars, the kinetic and the analytical parameters were evaluated under DET and MET operation modes. These results together with those obtained from long term operational stability measurements showed that: (i) for all nine investigated sugars the sensitivity was higher for MET than for DET and for pH 5.2 compared to pH 7.0; (ii) irrespective of DET or MET operation mode, the sensitivity of the new enzyme towards the investigated sugars decreased in the following sequence: cellobiose > lactose > (cellotriose approximate to cellopentaose) > > (maltotriose approximate to maltotetraose approximate to maltopentaose) > (maltose approximate to glucose); (iii) for all tested substrates, the apparent CDH affinity was roughly higher in DET than in MET operation mode. (C) 2012 Elsevier B.V. All rights reserved.
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| 25. |
- Krikstolaityte, Vida, et al.
(författare)
-
Bioelectrocatalytic reduction of oxygen at gold nanoparticles modified with laccase
- 2014
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 95, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- To characterise bioelectrocatalytic oxygen reduction at gold nanoparticles (AuNPs) modified with Trametes hirsuta laccase (ThLc) combined electrochemical and quartz crystal microbalance measurements have been used. The electrodes with different degrees of AuNP-monolayer coverage, theta, have been studied. In every case of theta close to theoretically possible 44 ThLc molecules adsorbed at 22 nm diameter AuNP. The bioelectrocatalytic current was recalculated down to the current at a single AuNR Unexpectedly, the current at a single AuNP was higher when theta was higher. The maximum current reached at a single AuNP was 31.10(-18) A which corresponds to the enzyme turnover (k(cat)) 13 s(-1). This rate is lower than the homogeneous ThLc turnover (190 s(-1)) suggesting partial denaturation of ThLc upon adsorption or that some ThLc are not in DET contact with the electrode surface
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| 26. |
- Lamberg, P., et al.
(författare)
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Electrical activity of cellobiose dehydrogenase adsorbed on thiols : Influence of charge and hydrophobicity
- 2017
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 115, s. 26-32
-
Tidskriftsartikel (refereegranskat)abstract
- The interface between protein and material surface is of great research interest in applications varying from implants, tissue engineering to bioelectronics. Maintaining functionality of bioelements depends greatly on the immobilization process. In the present study direct electron transfer of cellobiose dehydrogenase from Humicola insolens (HiCDH), adsorbed on four different self-assembled monolayers (SAMs) formed by 5-6 chain length carbon thiols varying in terminal group structure was investigated. By using a combination of quartz crystal micro balance with dissipation, ellipsometry and electrochemistry the formation and function of the HiCDH film was studied. It was found that the presence of charged pyridinium groups was needed to successfully establish direct electron contact between the enzyme and electrode. SAMs formed from hydrophilic charged thiols achieved nearly two times higher current densities compared to hydrophobic charged thiols. Additionally, the results also indicated proportionality between HiCDH catalytic constant and water content of the enzyme film. Enzyme films on charged pyridine thiols had smaller variations in water content and viscoelastic properties than films adsorbed on the more hydrophobic thiols. This work highlights several perspectives on the underlying factors affecting performance of immobilized HiCDH. (C) 2017 Elsevier B.V. All rights reserved.
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| 27. |
- Muresan, Laura, et al.
(författare)
-
Monitoring of glucose and glutamate using enzyme microstructures and scanning electrochemical microscopy.
- 2009
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76, s. 81-86
-
Tidskriftsartikel (refereegranskat)abstract
- Glucose oxidase and glutamate oxidase lines, with typical width of 100 microm, were patterned on gold surfaces using a micro-dispensing system, by shooting 100 pl droplets of the corresponding enzyme solutions. The probe of a scanning electrochemical microscope (SECM) was then carefully positioned in the close proximity of the enzyme microstructure and poised to +600 mV vs. Ag/AgCl, KCl 0.1 M. The H(2)O(2), generated by the enzyme lines at different concentrations of glucose and glutamate in the surrounding solution, was sequentially monitored. Reproducible calibration curves for glucose and glutamate were obtained in one single experiment, proving that the combination of enzyme microstructures with SECM can provide a new way of achieving multianalyte detection.
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| 28. |
- Mårtensson, Christoffer, et al.
(författare)
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Ubiquinone-10 in gold-immobilized lipid membrane structures acts as a sensor for acetylcholine and other tetraalkylammonium cations
- 2012
-
Ingår i: Bioelectrochemistry. - Amsterdam : Elsevier. - 1567-5394 .- 1878-562X. ; 88, s. 171-180
-
Tidskriftsartikel (refereegranskat)abstract
- It is reported that the reduction of ubiquinone incorporated into supported lipid bilayers and into immobilized liposome layers on gold electrodes is kinetically and thermodynamically enhanced by the presence of acetylcholine and tetrabutylammonium (TBA+) in solution. The reduction peak and the mid-peak potentials of the redox reactions, determined by cyclic voltammetry, are displaced towards more positive potentials by approximately 500 and 250 mV, respectively, in the case of TBA+; and by approximately 750 and 530 mV, respectively, in the case of acetylcholine. The intensity of the signal varies with the cation concentration, allowing for quantitative determinations in the millimolar range. It is proposed that the enhanced reduction of ubiquinone arises from the formation of tetraalkylammonium cation–ubiquinone radical anion ion-pairs. Electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurements confirmed that the potential shift and the intensity of the redox signal are coupled with the adsorption of the tetraalkylammonium cations on the lipid membrane. The Langmuir adsorption equilibrium constant (K) of TBA+ on lipid membranes at physiological pH is determined. In supported lipid bilayers K = 440.7 ± 160 M− 1, while in an immobilized liposome layer K = 35.53 ± 3.53 M− 1.
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| 29. |
- Pita, Marcos, et al.
(författare)
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Oxygen biosensor based on bilirubin oxidase immobilized on a nanostructured gold electrode
- 2013
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 94, s. 69-74
-
Tidskriftsartikel (refereegranskat)abstract
- Gold disk electrodes modified with gold nanoparticles have been used as a scaffold for the covalent immobilization of bilirubin oxidase. The nanostructured bioelectrodes were tested as mediator-less biosensors for oxygen in a buffer that mimics the content and the compn. of human physiol. fluids. Chronoamperometry measurements showed a detection limit towards oxygen of 6 ± 1 μM with a linear range of 6-300 μM, i.e. exceeding usual physiol. ranges of oxygen in human tissues and fluids. The biosensor presented is the first ever-reported oxygen amperometric biosensor based on direct electron transfer of bilirubin oxidase.
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| 30. |
- Psotta, Carolin, et al.
(författare)
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Continuous ex vivo glucose sensing in human physiological fluids using an enzymatic sensor in a vein replica
- 2023
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 152
-
Tidskriftsartikel (refereegranskat)abstract
- Managing blood glucose can affect important clinical outcomes during the intraoperative phase of surgery. However, currently available instruments for glucose monitoring during surgery are few and not optimized for the specific application. Here we report an attempt to exploit an enzymatic sensor in a vein replica that could continuously monitor glucose level in an authentic human bloodstream. First, detailed investigations of the superficial venous systems of volunteers were carried out using ocular and palpating examinations, as well as advanced ultrasound measurements. Second, a tubular glucose-sensitive biosensor mimicking a venous system was designed and tested. Almost ideal linear dependence of current output on glucose concentration in phosphate buffer saline was obtained in the range 2.2-22.0 mM, whereas the dependence in human plasma was less linear. Finally, the developed biosensor was investigated in whole blood under homeostatic conditions. A specific correlation was found between the current output and glucose concentration at the initial stage of the biodevice operation. However, with time, blood coagulation during measurements negatively affected the performance of the biodevice. When the experimental results were remodeled to predict the response without the influence of blood coagulation, the sensor output closely followed the blood glucose level.
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| 31. |
- Rafighi, Parvin, et al.
(författare)
-
A novel membraneless β-glucan/O2 enzymatic fuel cell based on β-glucosidase (RmBgl3B)/pyranose dehydrogenase (AmPDH) co-immobilized onto buckypaper electrode
- 2022
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 148
-
Tidskriftsartikel (refereegranskat)abstract
- A novel membraneless β-glucan/O2 enzymatic fuel cell was developed by combining a bioanode based on buckypaper modified with co-immobilized Agaricus meleagris pyranose dehydrogenase (AmPDH) and Rhodothermus marinus β-glucosidase (RmBgl3B) (RmBgl3B-AmPDH/buckypaper) with a biocathode based on solid graphite modified with Myrothecium verrucaria bilirubin oxidase (MvBOx/graphite). AmPDH was connected electrochemically with the buckypaper using an osmium redox polymer in a mediated reaction, whereas MvBOx was connected with graphite in a direct electron transfer reaction.The fuel for the bioanode was produced by enzymatic hydrolysis of β-glucan by the exoglucanase RmBgl3B into d-glucose, which in turn was enzymatically oxidised by AmPDH to generate a current response. This design allows to obtain an efficient enzymatic fuel cell, where the chemical energy converted into electrical energy is higher than the chemical energy stored in complex carbohydrate based fuel.The maximum power density of the assembled β-glucan/O2 biofuel cell reached 26.3 ± 4.6 μWcm−2 at 0.36 V in phosphate buffer containing 0.5 % (w/v) β-glucan at 40 °C with excellent stability retaining 68.6 % of its initial performance after 5 days. The result confirms that β-glucan can be employed as fuel in an enzymatic biofuel cell.
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| 32. |
- Rajendran, Sriram Thoppe, et al.
(författare)
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Tissue-based biosensor for monitoring the antioxidant effect of orally administered drugs in the intestine
- 2020
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 138
-
Tidskriftsartikel (refereegranskat)abstract
- For a better understanding of the effect of drugs and their interaction with cells and tissues, there is a need for in vitro and ex vivo model systems which enables studying these events. There are several in vitro methods available to evaluate the antioxidant activity; however, these methods do not factor in the complex in vivo physiology. Here we present an intestinal tissue modified oxygen electrode, used for the detection of the antioxidant effect of orally administered drugs in the presence of H2O2. Antioxidants are essential in the defense against oxidative stress, more specifically against reactive oxygen species such as H2O2. Due to the presence of native catalase in the intestine, with the tissue-based biosensor we were able to detect H2O2 in the range between 50 and 500 µM. The reproducibility of the sensor based on the calculated relative standard deviations was 15 ± 6%. We found that the O2 production by catalase from H2O2 was reduced in the presence of a well-known antioxidant, quinol. This indirectly detected antioxidant activity was also observed in the case of orally administered drugs with a reported anti-inflammatory effect such as mesalazine and paracetamol, while no antioxidant activity was recorded with aspirin and metformin.
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| 33. |
- Rems, Lea, et al.
(författare)
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The contribution of lipid peroxidation to membrane permeability in electropermeabilization : A molecular dynamics study
- 2019
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 125, s. 46-57
-
Tidskriftsartikel (refereegranskat)abstract
- Electroporation or electropermeabilization is a technique that enables transient increase in the cell membrane permeability by exposing cells to pulsed electric field. However, the molecular mechanisms of the long-lived cell membrane permeability, which persists on the minutes time scale after the pulse treatment, remain elusive. Experimental studies have suggested that lipid peroxidation could present a mechanism of this prolonged membrane permeabilization. In this study we make the first important step in quantifying the possible contribution of lipid peroxidation to electropermeabilization. We use free energy calculations to quantify the permeability and conductance of bilayers, containing an increasing percentage of hydroperoxide lipid derivatives, to sodium and chloride ions. We then compare our calculations to experimental measurements on electropermeabilized cells. Our results show that the permeability and conductance increase dramatically by several orders of magnitude in peroxidized bilayers. Yet this increase is not sufficient to reasonably account for the entire range of experimental measurements. Nevertheless, lipid peroxidation might be considered an important mechanism of prolonged membrane permeabilization, if exposure of cells to high voltage electric pulses leads to secondary lipid peroxidation products. Our analysis calls for experimental studies, which will determine the type and amount of lipid peroxidation products in electropermeabilized cell membranes.
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| 34. |
- Salaj-Kosla, Urszula, et al.
(författare)
-
Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes
- 2013
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 91, s. 15-20
-
Tidskriftsartikel (refereegranskat)abstract
- The enzyme Trametes hirsuta laccase undergoes direct electron transfer at unmodified nanoporous gold electrodes, displaying a c.d. of 28 μA/cm2. The response indicates that ThLc was immobilized at the surface of the nanopores in a manner which promoted direct electron transfer, in contrast to the absence of a response at unmodified polycryst. gold electrodes. The bioelectrocatalytic activity of ThLc modified nanoporous gold electrodes was strongly dependent on the presence of halide ions. Fluoride completely inhibited the enzymic response, whereas in the presence of 150 mM Cl-, the current was reduced to 50% of the response in the absence of Cl-. The current increased by 40% when the temp. was increased from 20 °C to 37 °C. The response is limited by enzymic and/or enzyme electrode kinetics and is 30% of that obsd. for ThLc co-immobilized with an osmium redox polymer.
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| 35. |
- Sarauli, David, et al.
(författare)
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Investigation of the mediated electron transfer mechanism of cellobiose dehydrogenase at cytochrome c-modified gold electrodes
- 2012
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 87, s. 9-14
-
Tidskriftsartikel (refereegranskat)abstract
- The present study reports on the comparison of direct and mediated electron transfer pathways in the interaction of the fungal enzyme cellobiose dehydrogenase (CDH) with the redox protein cytochrome c (cyt c) immobilised at a modified gold electrode surface. Two types of CDHs were chosen for this investigation: a basidiomycete (white rot) CDH from Trametes villosa and a recently discovered ascomycete from the thermophilic fungus Corynascus thermophilus. The choice was based on the pH-dependent interaction of these enzymes with cyt c in solution containing the substrate cellobiose (CB). Both enzymes show rather similar catalytic behaviour at lower pH, dominated by a direct electron exchange with the electrode. With increasing pH, however, also cyt c-mediated electron transfer becomes possible. The pH-dependent behaviour in the presence and in the absence of cyt c is analysed and the potential reaction mechanism for the two enzymes with a different pH-behaviour is discussed. (c) 2011 Published by Elsevier B.V.
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| 36. |
- Shipovskov, Stepan, et al.
(författare)
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Recombinant horseradish peroxidase- and cytochrome c-based two-electrode system for detection of superoxide radicals
- 2004
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 63:1-2, s. 277-280
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Tidskriftsartikel (refereegranskat)abstract
- The reliable detection of a superoxide anion radical O-2(.-) - is complicated by its spontaneous dismutation reaction to H2O2 at acidic pHs. To simultaneously detect both O-2(.-) and H2O2 produced in the course of its spontaneous dismutation, an electrochemical two-electrode system based on cytochrome c (cyt c) and recombinant horseradish peroxidase (rHRP) was applied. Therewith, a limited applicability of the cyt c system for the reliable monitoring of O-2(.-) in acidic and neutral solutions was shown. It was demonstrated that both the reaction of O-2(.-) dismutation to H2O2 and the reaction between the formed H2O2 and O-2(.-) chemically decrease the amount of the initially present O-2(.-) decreasing the sensitivity and reliability of the electrochemical detection at acidic pH. However, by appropriately varying solution pH, the concentration of O-2(.-) - initially injected in the system can be estimated from the analysis of calibration curves for H2O2 obtained with highly sensitive rHRP-modified electrode system at pH 6.0 and 7.0. (C) 2004 Elsevier B.V. All rights reserved.
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| 37. |
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| 38. |
- Shleev, Sergey, et al.
(författare)
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Direct electron transfer reactions of laccases from different origins on carbon electrodes
- 2005
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 67:1, s. 115-124
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical studies of laccases from basidiomycetes, i.e., Trametes hirsuta, Trametes ochracea, Coriolopsis fulvocinerea, Cerrena maxima, and Cerrena unicolor, have been performed. Direct (mediatorless) electrochemistry of laccases on graphite electrodes has been investigated with cyclic voltammetry, square wave voltammetry as well as potentiometry. For all mentioned high potential laccases direct electron transfer (DET) has been registered at spectrographic graphite and highly ordered pyrolytic graphite electrodes. The characteristics of DET reactions of the enzymes were analysed under aerobic and anaerobic conditions. It is shown that the T I site of the laccase is the primary electron acceptor, both in solution (homogenous case) and at surface of the graphite electrode (heterogeneous case). A mechanism of ET for the process of the electroreduction of oxygen at the laccase-modified graphite electrodes is proposed and the similarity of this heterogeneous process to the laccase catalysed oxygen reduction homogeneous reaction is concluded. (c) 2005 Elsevier B.V. All rights reserved.
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| 39. |
- Shumakovich, G. P., et al.
(författare)
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Electrochemistry and kinetics of fungal laccase mediators
- 2006
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 69:1, s. 16-24
-
Tidskriftsartikel (refereegranskat)abstract
- The screening of potential redox mediators for laccase was performed using homogeneous Trametes hirsuta laccase. Heterogeneous (electrochemical) and homogeneous (oxidation by laccase) reactions of the different types of the enhancers (mediators) of the enzyme were investigated. It was discovered that derivatives of phenyl-methyl-pyrazolones and benzoic acid, as well as N-hydroxynaphthalimide were efficient substrates for the laccase. The characterization of several representatives from each class was carried out using electrochemical and enzyme kinetics methods. The kinetic parameters for the oxidation of phenyl-methyl-pyrazolones and 3-(6-hylroxy)-aminobenzoic acid were comparable to those for 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation by the laccase, whereas the rate of enzymatic oxidation of N-hydroxynaphthalimide was sufficiently lower. Electrochemical experiments demonstrated that only oxidation of phenyl-methyl-pyrazolones and N-hydroxynaphthalimide yielded several high-potential intermediates capable of oxidizing veratryl alcohol, which was used as a lignin model substrate, whereas derivatives of benzoic acid showed low-potential intermediate, which was not able to oxidized lignin model compound. Phenyl-methyl-pyrazolones was about 50% as effective in degrading veratryl alcohol compared to ABTS as judged from HPLC kinetic studies, whereas N-hydroxynaphthalimide showed the same efficiency as ABTS. Phenyl-methyl-pyrazolones and hydroxynaphthalimides may be of commercial interest for oxidoreductase-catalyzed biodegradation of different xenobiotics. (c) 2005 Elsevier B.V. All rights reserved.
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| 40. |
- Stoica, Leonard, et al.
(författare)
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Electrochemical evidence of self-substrate inhibition as functions regulation for cellobiose dehydrogenase from Phanerochaete chrysosporium
- 2009
-
Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 76:1-2, s. 42-52
-
Tidskriftsartikel (refereegranskat)abstract
- The reaction mechanism of cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium, adsorbed on graphite electrodes, was investigated by following its catalytic reaction with cellobiose registered in both direct and mediated electron transfer modes between the enzyme and the electrode. A wall-jet flow through amperometric cell housing the CDH-modified graphite electrode was connected to a single line flow injection system. In the present study, it is proven that cellobiose, at concentrations higher than 200 μM, competes for the reduced state of the FAD cofactor and it slows down the transfer of electrons to any 2e−/H+ acceptors or further to the heme cofactor, via the internal electron transfer pathway. Based on and proven by electrochemical results, a kinetic model of substrate inhibition is proposed and supported by the agreement between simulation of plots and experimental data. The implications of this kinetic model, called pseudo-ping-pong mechanism, on the possible functions CDH are also discussed. The enzyme exhibits catalytic activity also for lactose, but in contrast to cellobiose, this sugar does not inhibit the enzyme. This suggests that even if some other substrates are coincidentally oxidized by CDH, however, they do not trigger all the possible natural functions of the enzyme. In this respect, cellobiose is regarded as the natural substrate of CDH.
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| 41. |
- Timur, Suna, et al.
(författare)
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Electrical wiring of Pseudomonas putida and Pseudomonas fluorescens with osmium redox polymers
- 2007
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 71:1, s. 38-45
-
Tidskriftsartikel (refereegranskat)abstract
- Two different flexible osmium redox polymers; poly(1-vinylimidazole)(12)-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)(2)Cl-2](2 +/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)(3)](2+/3+) (osmium redox polymer II) were investigated for their ability to efficiently "wire" Pseudomonas putida ATCC 126633 and Pseudomonas fluorescens (P putida DSM 6521), which are well-known phenol degrading organisms, when entrapped onto cysteamine modified gold electrodes. The two Os-polymers differ in redox potential and the length of the side chains, where the OS2+/3+-functionalities are located. The bacterial cells were adapted to grow in the presence of phenol as the sole source of organic carbon. The performance of the redox polymers as mediators was investigated for making microbial sensors. The analytical characteristics of the microbial sensors were evaluated for determination of catechol, phenol and glucose as substrates in both batch analysis and flow analysis mode.
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| 42. |
- Trashin, Stanislav A., et al.
(författare)
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Improvement of direct bioelectrocatalysis by cellobiose dehydrogenase on screen printed graphite electrodes using polyaniline modification
- 2009
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76:1-2, s. 87-92
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Tidskriftsartikel (refereegranskat)abstract
- Modification of graphite based screen printed electrodes (SPEs) by electrosynthesised polyaniline (PANI) has been applied to improve the electron exchange between cellobiose dehydrogenase (CDH, EC 1.1.99.18) from the ascomycete Myriococcum thermophilum and the surface of the SPE. The redox intermediate layer of the conducting polymer promotes the bioelectrocatalysis providing a higher current for lactose oxidation at a lower potential compared to CDH immobilised on a plain SPE. The current of the SPE vertical bar PANI vertical bar CDH electrode was more than 5 times higher as compared to that of a SPE vertical bar CDH electrode at a potential of 0 mV vs. Ag vertical bar AgCl. When comparing the response obtained through direct electron transfer with that obtained through mediated electron transfer. it was clearly observed that the improved current of the SPE vertical bar PANI vertical bar CDH electrode is due to the specific role of PANI, rather than caused by a rise of enzyme loading. The operational stability of the enzyme electrode based on PANI modified SPE was 5 times higher compared with that based on plain SPE. (C) 2009 Elsevier B.V. All rights reserved
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| 43. |
- Ušaj, Marko, et al.
(författare)
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Electrofusion of B16-F1 and CHO cells: the comparison of the pulse first and contact first protocols
- 2013
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 89, s. 34-41
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Tidskriftsartikel (refereegranskat)abstract
- High voltage electric pulses induce permeabilisation (i.e. electroporation) of cell membranes. Electric pulses also induce fusion of cells which are in contact. Contacts between cells can be established before electroporation, in so-called contact first or after electroporation in pulse first protocol. The lowest fusion yield was obtained by pulse first protocol (0.8%±0.3%) and it was only detected by phase contrast microscopy. Higher fusion yield detected by fluorescence microscopy was obtained by contact first protocol. The highest fusion yield (15%) was obtained by modified adherence method whereas fusion yield obtained by dielectrophoresis was lower (4%). The results are in agreement with current understanding of electrofusion process and with existing electrochemical models. Our data indicate that probability of stalk formation leading to fusion pores and cytoplasmic mixing is higher in contact first protocol where cells in contact are exposed to electric pulses. Another contribution of present study is the comparison of two detection methods. Although fusion yield can be more precisely determined with fluorescence microscopy we should note that by using this detection method single coloured fused cells cannot be detected. Therefore low fusion yields are more reliably detected by phase contrast microscopy.
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| 44. |
- Xafenias, Nikolaos, 1981, et al.
(författare)
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Enhancement of anaerobic lysine production in Corynebacterium glutamicum electrofermentations
- 2017
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1567-5394 .- 1878-562X. ; 117C, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that application of electric potential can affect lysine producing fermentations, although experimental evidence is lacking. To study this hypothesis we used the lysine producer Corynebacterium glutamicum ZW04, and we exposed it to 12 different conditions regarding anaerobic gas environment, applied electrode potential (cathodic, open circuit, anodic), redox mediator and nitrate presence. The gas environment was found to play a major role, with CO2 leading to double the lysine concentrations and yields when compared to N2. Electrode potentials also played a major role, with reductive conditions doubling the titers and increasing the yields of lysine up to 4 times. Addition of the redox mediator anthraquinone-2-sulfonate (AQ2S) under the presence of CO2 and reductive conditions led to additional doubling of the titers, although the yields were not altered considerably. This study demonstrates for the first time that cathodic electrode conditions combined with CO2 and AQ2S as a redox mediator can significantly improve both the yields and the titers of lysine production of a C. glutamicum lysine producing strain, reaching levels that have only been achieved under aerobic conditions.
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| 45. |
- Yaropolov, A., et al.
(författare)
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Electroenzymatic reactions with oxygen on laccase-modified electrodes in anhydrous (pure) organic solvent
- 2007
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 70:2, s. 199-204
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Tidskriftsartikel (refereegranskat)abstract
- The electroenzymatic reactions of Trametes hirsuta laccase in the pure organic solvent dimethyl sulfoxide (DMSO) have been investigated within the framework for potential use as a catalytic reaction scheme for oxygen reduction. The bioelectrochemical characteristics of laccase were investigated in two different ways: (i) by studying the electroreduction of oxygen in anhydrous DMSO via a direct electron transfer mechanism without proton donors and (ii) by doing the same experiments in the presence of laccase substrates, which display in pure organic solvents both the properties of electron donors as well as the properties of weak acids. The results obtained with laccase in anhydrous DMSO were compared with those obtained previously in aqueous buffer. It was shown that in the absence of proton donors under oxygenated conditions, formation of superoxide anion radicals is prevented at bare glassy carbon and graphite electrodes with adsorbed laccase. The influence of the time for drying the laccase solution at the electrode surface on the electroreduction of oxygen was studied. Investigating the electroenzymatic oxidation reaction of catechol and hydroquinone in DMSO reveals the formation of various intermediates of the substrates with different electrochemical activity under oxygenated conditions. The influence of the content of aqueous buffer in the organic solvent on the electrochemical behaviour of hydroquinone/1,4-benzoquinone couple was also studied. (C) 2006 Elsevier B.V. All fights reserved.
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| 46. |
- Zafar, MNadeem, et al.
(författare)
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Wiring of pyranose dehydrogenase with osmium polymers of different redox potentials.
- 2010
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 80, s. 38-42
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Tidskriftsartikel (refereegranskat)abstract
- In this study, five different flexible osmium based redox polymers were investigated for their ability to efficiently "wire" the oxidoreductase pyranose dehydrogenase (PDH, EC 1.1.99.29) from Agaricus meleagris, on graphite electrodes for possible applications in biofuel cells. A series of newly synthesised osmium based redox polymers covering the potential range between -270 and +160mV vs. Ag|AgCl (0.1M KCl) was used. The performance of the redox polymers for enzyme wiring was investigated using glucose as substrate. The optimal operational conditions such as pH and potential were investigated.
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| 47. |
- Zebda, Abdelkader, et al.
(författare)
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Challenges for successful implantation of biofuel cells
- 2018
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Ingår i: Bioelectrochemistry. - : Elsevier. - 1567-5394 .- 1878-562X. ; 124, s. 57-72
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Forskningsöversikt (refereegranskat)abstract
- There is a growing interest in the design and engineering of operational biofuel cells that can be implanted. This review highlights the recent progress in the electrochemistry of biofuel cell technologies, but with a particular emphasis on the medical and physiological aspects that impact the biocompatibility of biofuel cells operating inside a living body. We discuss the challenge of supplying power to implantable medical devices, with regard to the limitations of lithium battery technology and why implantable biofuel cells can be a promising alternative to provide the levels of power required for medical devices. In addition to the challenge of designing a biofuel cell that provides a stable level of sufficient power, the review highlights the biocompatibility and biofouling problems of implanting a biofuel cell that have a major impact on the availability of the substrates inside body that provide fuel for the biofuel cell. These physiological challenges and associated ethical considerations are essential to consider for biofuel cells that are designed to be implanted for long-term operation inside a living animal and eventually to human clinical applications. (C) 2018 The Authors. Published by Elsevier B.V.
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| 48. |
- Zor, Kinga, et al.
(författare)
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Label free capacitive immunosensor for detecting calpastatin - A meat tenderness biomarker.
- 2009
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76:1-2, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- An immunological capacitive biosensor for calpastatin was developed, optimized and applied for the analysis of meat extract samples. Anti-calpastatin antibody was immobilized on a gold electrode modified with a self-assembled monolayer of mercaptoundecanoic acid and Protein A from Staphylococcus aureus, and the obtained immunosensor was inserted as the working electrode in an electrochemical cell of a flow injection system. The dynamic range of the sensor was 20 to 160 ng/mL calpastatin. The electrode could be regenerated and re-used for more than 7 days with minimal reduction in sensitivity. For the analysis of real samples, the target analyte was extracted from the Longissimus dorsi muscle from beef carcasses directly after slaughtering. The extract was analyzed both with the developed immunosensor and microtiter plate ELISA, and a good correlation was obtained. However the immunosensor offers advantages of speed, simplicity, sensitivity and possibility for miniaturization over conventional assays for calpastatin quantification.
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| 49. |
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| 50. |
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