| 1. |
- Antiochia, Riccarda, et al.
(författare)
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Composite Material Based on Macroporous Polyaniline and Osmium Redox Complex for Biosensor Development
- 2014
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Ingår i: Electroanalysis. - : Wiley. - 1040-0397. ; 26:7, s. 1623-1630
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Tidskriftsartikel (refereegranskat)abstract
- Here the feasibility of layers based on the conducting polymer polyaniline (PANI) as component of glucose biosensors using glucose oxidase (GOx) as enzyme and [Os(bpy)(2)(4-aminomethylpyridine)Cl]PF6 (OsCmplx) as electrochemical mediator, is evaluated. Particularly, PANI was employed to obtain a nanostructured macroporous material (m-PANI) around polystyrene nanoparticles taken as template and the mediator was co-immobilized during the polymerizing procedure. The GOx biosensor based on OsCmplx modified m-PANI provides a linear response to glucose concentration in the range 5 up to 65 mM with a sensitivity of 3.54 mu A/mM/cm(2) (on a projected geometric area=0.07 cm(2)), an LOD of 0.8 mM and a good precision (%RSD <= 7, n=5); the biosensor is stable showing a decrease of 10% to the value of the sensitivity after 15 days of use and of about 50% after 40 days.
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| 2. |
- Aslan, Sema, et al.
(författare)
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Development of a Bioanode for Microbial Fuel Cells Based on the Combination of a MWCNT-Au-Pt Hybrid Nanomaterial, an Osmium Redox Polymer and Gluconobacter oxydans DSM 2343 Cells
- 2017
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Ingår i: ChemistrySelect. - : Wiley. - 2365-6549. ; 2:36, s. 12034-12040
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a carbon felt electrode (CFE) was modified with a multiwalled carbon nanotube-gold-platinum (MWCNT-Au-Pt) hybrid nanomaterial and integrated with an osmium redox polymer (OsRP, [Os(2, 2’-bipyridine)2(poly-vinylimidazole)10Cl]Cl) and Gluconobacter oxydans DSM 2343 (G. oxydans) cells. The developed electrode was used as the bioanode in a 5.0 mM K3Fe(CN)6mediator containing phosphate buffer (pH 6.5) anolyte and combined with a Pt wire cathode in phosphoric acid medium (pH 3.5). As a result, a two chamber microbial fuel cell (MFC) was formed, in which an activated Nafion membrane was used as a proton exchange membrane. The OsRP/G.oxydans/MWCNT-Au-Pt/CFE based bioanode was electrochemically examined in differently deoxygenated bioanode chambers and additionally the amounts of hybrid nanomaterial and OsRP were optimized. In terms of MFC characteristics, it was found that an anaerobic OsRP/G.oxydans/MWCNT-Au-Pt/CFE bioanode based MFC had a maximum power density of 32.1 mW m-2(at 90 mV), a maximum current density of 1032 mA m-2and a charge transfer efficiency (E%) value of 22.30 (open circuit potential 180 mV).
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| 3. |
- Aslan, Sema, et al.
(författare)
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Development of an Osmium Redox Polymer Mediated Bioanode and Examination of Its Performance in Gluconobacter oxydans Based Microbial Fuel Cell
- 2017
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397. ; 29:6, s. 1651-1657
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Tidskriftsartikel (refereegranskat)abstract
- Gluconobacter oxydans (G. oxydans) cells together with an osmium redox polymer (ORP) [Osmium (2,2'-bipyridine)2(poly-vinylimidazole)10Cl]Cl were combined with a glassy carbon paste electrode (GCPE) to form a bioanode for a microbial fuel cell (MFC) based on G. oxydans. Although there are G.oxydans/ ORP combined bioanode in the literature, as far as it is known, this system is the first one where G.oxydans/ORP bioanode is combined with a cathode and a MFC is formed. After the optimization of experimental parameters, analytical characteristics of ORP/G. oxydans/GCPE bioanode were investigated. ORP/G. oxydans/GCPE showed two linear ranges for ethanol substrate as 1.0-30mM (R2=0.902) and 30-500mM (R2=0.997) and analytical range as 1.0-1000mM. Limit of detection (3.0s/m) and limit of quantification (10s/m) values were calculated as 1.29mM and 4.30mM respectively where the RSD value was 1.16% for n=5. Combining the developed bioanode in the presence of 5.0mM K3Fe(CN)6 mediator with a Pt wire cathode a double compartment MFC was obtained via a salt bridge. G. oxydans/GCPE bioanode based MFC had maximum power density of 0.133 μW cm-2 (at 33.5 mV), maximum current density as 8.73 μA cm-2 and OCP value of 156 mV. On the other hand, ORP/G. oxydans/GCPE based MFC showed maximum power density as 0.26 μW cm-2 (at 46.8 mV), maximum current density as 15.079 μA cm-2 and OCP value of 176 mV.
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| 4. |
- Bollella, Paolo, et al.
(författare)
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Highly sensitive, stable and selective hydrogen peroxide amperometric biosensors based on peroxidases from different sources wired by Os-polymer : A comparative study
- 2018
-
Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 314, s. 178-186
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Tidskriftsartikel (refereegranskat)abstract
- A comparison was made between two plant peroxidases, cationic horseradish peroxidase (HRP) and anionic tobacco peroxidase (TOP), combined with a highly cationic osmium polymer [Os(4,4'-dimethyl-2,2'-bipyridine)2poly(N-vinylimidazole)10Cl]+2/+ ([Os(dmp)PVI]+/2+) to develop highly sensitive, stable and selective hydrogen peroxide biosensors. The two different plant peroxidases were individually immobilized onto graphite rod (G) electrodes by a three steps drop-casting procedure consisting of the subsequent deposition of an aqueous solution of ([Os(dmp)PVI]+/2+), followed by a solution of poly(ethyleneglycol) diglycidyl ether (PEGDGE), used as a cross linking agent and finally an aliquot of a solution of cationic HRP or anionic TOP to make HRP/PEGDGE/[Os(dmp)PVI]+/2+/G and TOP/PEGDGE/[Os(dmp)PVI]+/2+/G based electrodes, respectively. Electrochemical experiments were carried out to investigate the influence of the surface charge of the enzyme and the charge of the polymer on the efficiency of the electron transfer (ET) between the enzyme and the wiring redox polymer and the efficiency for electrocatalytic reduction of H2O2. In the case of HRP a decrease in the ET rate was observed due to the repulsion between this enzyme and the polymer, both positively charged, whereas with TOP there was an enhanced ET rate due to the attraction between the anionic enzyme and the cationic polymer. The effects of enzyme loading and pH were investigated. Both peroxidase modified electrodes exhibited a wide dynamic response range (1-500μM H2O2) and a low detection limit (0.3μM H2O2). The TOP based electrode showed a higher sensitivity (470nAμM-1 cm-2) compared to that of the HRP based electrode (300nAμM-1 cm-2) and an improved long-term stability (decrease in 17.3% upon 30days compared with 50% for HRP). Both enzyme electrodes showed a response time of 3s. The HRP based sensor was more sensitive to the presence of phenolic compounds acting as alternative electron donors, whereas the TOP based sensor was virtually interference free. Both HRP and TOP based electrodes were successfully tested in contact lens cleaning samples and real "spiked" samples from different sources such as tap water, milk and dairy products.
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| 5. |
- Bunea, Ada-Ioana, et al.
(författare)
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Micropatterned Carbon-on-Quartz Electrode Chips for Photocurrent Generation from Thylakoid Membranes
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:7, s. 3313-3322
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Tidskriftsartikel (refereegranskat)abstract
- Harvesting the energy generated by photosynthetic organisms through light-dependent reactions is a significant step toward a sustainable future energy supply. Thylakoid membranes are the site of photosynthesis, and thus particularly suited for developing photo-bioelectrochemical cells. Novel electrode materials and geometries could potentially improve the efficiency of energy harvesting using thylakoid membranes. For commercial applications, electrodes with large surface areas are needed. Photolithographic patterning of a photoresist, followed by pyrolysis, is a flexible and fast approach for the fabrication of carbon electrodes with tailored properties. In this work, electrode chips consisting of patterned carbon supported on quartz were designed and fabricated. The patterned electrode area is 1 cm2, and the measurement chamber footprint is 0.5 cm2, 1 order of magnitude larger than previously tested electrodes for thylakoid membrane immobilization. The use of a transparent substrate allows back-side illumination, protecting the bioelectrochemical system from the environment and vice versa. Two different mediators, monomeric ([Ru(NH3)6]3+) and polymeric ([Os(2,2′-bipyridine)2-poly(N-vinylimidazole)10Cl]+/2+), are used for evaluating photocurrent generation from thylakoid membranes with different electrode geometries. Current densities up to 71 μA cm–2 are measured upon illumination through the transparent electrode chip with solar simulated irradiance (1000 W m–2).
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| 6. |
- Darus, Libertus, et al.
(författare)
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Redox-polymers enable uninterrupted day/night photo-driven electricity generation in biophotovoltaic devices
- 2017
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:3, s. 3037-3040
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Tidskriftsartikel (refereegranskat)abstract
- Biophotovoltaic devices modified with immobilized polymeric osmium/azine redox-mediators exhibited a considerable electrical output enhancement (64/43-fold under light/dark conditions, respectively). More importantly, the systems exhibited uninterrupted current generation at same magnitude levels during day/night cycles, paving the way toward solar energy conversion bio-panels that will not require energy storage peripherals.
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| 7. |
- Falk, Magnus, et al.
(författare)
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Self-powered wireless carbohydrate/oxygen sensitive biodevice based on radio signal transmission
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 9:10, s. e109104/1-e109104/9
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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 sep. sensing bioelectrodes, supplied with elec. energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymic 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, resp. to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen contg. buffer. In addn., 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 contg. different concns. of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concns. in buffers were changed, using only an enzymic fuel cell as a power supply.
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| 8. |
- Figueiredo, Carina, et al.
(författare)
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Effect of Protection Polymer Coatings on the Performance of an Amperometric Galactose Biosensor in Human Plasma
- 2024
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Ingår i: Biosensors. - 2079-6374. ; 14:4
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Tidskriftsartikel (refereegranskat)abstract
- Galactose monitoring in individuals allows the prevention of harsh health conditions related to hereditary metabolic diseases like galactosemia. Current methods of galactose detection need development to obtain cheaper, more reliable, and more specific sensors. Enzyme-containing amperometric sensors based on galactose oxidase activity are a promising approach, which can be enhanced by means of their inclusion in a redox polymer coating. This strategy simultaneously allows the immobilization of the biocatalyst to the electroactive surface and hosts the electron shuttling units. An additional deposition of capping polymers prevents external interferences like ascorbic or uric acid as well as biofouling when measuring in physiological fuels. This work studies the protection effect of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate (MPC) and polyvinylimidazole-polysulfostyrene (P(VI-SS)) when incorporated in the biosensor design for the detection of galactose in human plasma.
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| 9. |
- Gonaus, Christoph, et al.
(författare)
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Analysis of Agaricus meleagris pyranose dehydrogenase N-glycosylation sites and performance of partially non-glycosylated enzymes
- 2017
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 99, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- Pyranose Dehydrogenase 1 from the basidiomycete Agaricus meleagris (AmPDH1) is an oxidoreductase capable of oxidizing a broad variety of sugars. Due to this and its ability of dioxidation of substrates and no side production of hydrogen peroxide, it is studied for use in enzymatic bio-fuel cells. In-vitro deglycosylated AmPDH1 as well as knock-out mutants of the N-glycosylation sites N75 and N175, near the active site entrance, were previously shown to improve achievable current densities of graphite electrodes modified with AmPDH1 and an osmium redox polymer acting as a redox mediator, up to 10-fold. For a better understanding of the role of N-glycosylation of AmPDH1, a systematic set of N-glycosylation site mutants was investigated in this work, regarding expression efficiency, enzyme activity and stability. Furthermore, the site specific extend of N-glycosylation was compared between native and recombinant wild type AmPDH1. Knocking out the site N252 prevented the attachment of significantly extended N-glycan structures as detected on polyacrylamide gel electrophoresis, but did not significantly alter enzyme performance on modified electrodes. This suggests that not the molecule size but other factors like accessibility of the active site improved performance of deglycosylated AmPDH1/osmium redox polymer modified electrodes. A fourth N-glycosylation site of AmPDH1 could be confirmed by mass spectrometry at N319, which appeared to be conserved in related fungal pyranose dehydrogenases but not in other members of the glucose-methanol-choline oxidoreductase structural family. This site was shown to be the only one that is essential for functional recombinant expression of the enzyme.
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| 10. |
- Hamidi, Hassan, et al.
(författare)
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Photocurrent Generation from Thylakoid Membranes on Osmium-Redox-Polymer-Modified Electrodes.
- 2015
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 8:6, s. 990-993
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Tidskriftsartikel (refereegranskat)abstract
- Thylakoid membranes (TMs) are uniquely suited for photosynthesis owing to their distinctive structure and composition. Substantial efforts have been directed towards use of isolated photosynthetic reaction centers (PRCs) for solar energy harvesting, however, few studies investigate the communication between whole TMs and electrode surfaces, due to their complex structure. Here we report on a promising approach to generate photosynthesis-derived bioelectricity upon illumination of TMs wired with an osmium-redox-polymer modified graphite electrode, and generate a photocurrent density of 42.4 μA cm(-2) .
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| 11. |
- Hasan, Kamrul, et al.
(författare)
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Electrochemical Communication Between Electrodes and Rhodobacter capsulatus Grown in Different Metabolic Modes
- 2015
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Ingår i: Electroanalysis. - : Wiley. - 1040-0397. ; 27:1, s. 118-127
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Tidskriftsartikel (refereegranskat)abstract
- The majority of efforts on microbial and photosynthetic microbial fuel cells are both curiosity driven and made to possibly meet the future growing demand for sustainable energy. The most metabolically versatile purple bacteria Rhodobacter capsulatus is a potential candidate for this purpose. However, utilizing bacteria in such systems requires efficient electronic transfer communication between the microbial cells and the electrodes, which is one of the greatest challenges. Previous studies demonstrated that osmium redox polymers (ORPs) could be used for extracellular electron transfer between the cells and electrodes. Recently, heterotrophically grown R. capsulatus has been wired with ORP modified electrodes. Here in this communication, we report electron transfer from R. capsulatus grown under heterotrophic as well as under photoheterotrophic conditions to electrodes. The cells, immobilized on bare graphite and ORP modified graphite electrodes, were excited with visible light and subsequent photosynthetic electron transfer was recorded using cyclic voltammetric and chronoamperometric measurements. Photoheterotrophically grown R. capsulatus cells on bare graphite generate a significant photocurrent density of 3.46 mu A cm(-2), whereas on an ORP modified electrode the current density increases to 8.46 mu A cm(-2). Furthermore, when 1 mM p-benzoquinone is added to the electrolyte the photocurrent density reaches 12.25 mu A cm(-2). Our results could have significant implications in photosynthetic energy conversion and in development of photobioelectrochemical devices.
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| 12. |
- 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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| 13. |
- Hasan, Kamrul, et al.
(författare)
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Electrochemical communication between microbial cells and electrodes via osmium redox systems.
- 2012
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Ingår i: Biochemical Society Transactions. - 0300-5127. ; 40:6, s. 1330-1335
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical communication between micro-organisms and electrodes is the integral and fundamental part of BESs (bioelectrochemical systems). The immobilization of bacterial cells on the electrode and ensuring efficient electron transfer to the electrode via a mediator are decisive features of mediated electrochemical biosensors. Notably, mediator-based systems are essential to extract electrons from the non-exoelectrogens, a major group of microbes in Nature. The advantage of using polymeric mediators over diffusible mediators led to the design of osmium redox polymers. Their successful use in enzyme-based biosensors and BFCs (biofuel cells) paved the way for exploring their use in microbial BESs. The present mini-review focuses on osmium-bound redox systems used to date in microbial BESs and their role in shuttling electrons from viable microbial cells to electrodes.
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| 14. |
- Hasan, Kamrul, et al.
(författare)
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Evaluation of Photocurrent Generation from Different Photosynthetic Organisms
- 2017
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Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 4:2, s. 412-417
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Tidskriftsartikel (refereegranskat)abstract
- Biological photovoltaics (BPVs) are emerging as a potential sustainable energy-generating technology to convert solar energy into electrical energy. Although a great variety of photosynthetic biomaterials were studied in BPVs, cyanobacteria are considered as superior candidates because of their simpler physiology. To facilitate extracellular electron transfer (EET) from cyanobacteria to electrodes is the greatest challenge to improving the performance of BPVs. However, a systematic study comparing the photo-excited EET from such organisms is not yet reported. Here we report on a comparison of photocurrent density generated by benthic cyanobacteria, that is, two species of Leptolyngbya sp. (CAWBG62 and CAWBG100), one species from the order Chroococcales (CAWBG64), and a eukaryotic algae, Paulschulzia pseudovolvox (UKE). This algae and CAWBG100 were sourced from New Zealand, CAWBG62 and CAWBG64 were from Antarctica. We demonstrate EET mediated by three different electron transfer (ET) mediating systems on graphite electrodes. These are as follows: (I) [Os(2,2’-(bipyridine)2(polyvinyl-imidazole)10Cl]+/2+ (1:9) [Os-(bpy)PVI] (II) p-benzoquinone (PBQ) (III) [Os-(bpy)PVI] together with PBQ. The maximum photocurrent density of 47.2 μA cm−2 was obtained from CAWBG64 mediated by (III) [Os-(bpy)PVI] together with PBQ.
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| 15. |
- Hasan, Kamrul, et al.
(författare)
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Photo-electrochemical communication between cyanobacteria (Leptolyngbia sp.) and osmium redox polymer modified electrodes.
- 2014
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084. ; 16:45, s. 24676-24680
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic microbial fuel cells (PMFCs) are an emerging technology for renewable solar energy conversion. Major efforts have been made to explore the electrogenic activity of cyanobacteria, mostly using practically unsustainable reagents. Here we report on photocurrent generation (≈8.64 μA cm(-2)) from cyanobacteria immobilized on electrodes modified with an efficient electron mediator, an Os(2+/3+) redox polymer. Upon addition of ferricyanide to the electrolyte, cyanobacteria generate the maximum current density of ≈48.2 μA cm(-2).
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| 16. |
- Hasan, Kamrul, et al.
(författare)
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Photoelectrochemical Wiring of Paulschulzia pseudovolvox (Algae) to Osmium Polymer Modified Electrodes for Harnessing Solar Energy
- 2015
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832. ; 5:22
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Tidskriftsartikel (refereegranskat)abstract
- Studies on biological photovoltaics based on intact organisms are challenging and in most cases include diffusing mediators to facilitate electrochemical communication with electrodes. However, using such mediators is impractical. Instead, surface confined Os-polymers have been successfully used in electrochemical studies including oxidoreductases and bacterial cells but not with algae. Photoelectrogenic activity of a green alga, Paulschulzia pseudovolvox, immobilized on graphite or Os-polymer modified graphite is demonstrated. Direct electron transfer is revealed, when no mediator is added, between algae and electrodes with electrons emerging from photolysis of water via the cells to the electrode exhibiting a photocurrent density of 0.02 mu A cm(-2). Os-polymers with different redox potentials and structures are used to optimize the energy gap between the photosynthetic complexes of the cells and the Os-polymers and those of greater solubility, better accessibility with membranes, and relatively higher potentials yielded a photocurrent density of 0.44 mu A cm(-2). When benzoquinone is included to the electrolyte, the photocurrent density reaches 6.97 mu A cm(-2). The photocurrent density is improved to 11.50 mu A cm(-2), when the cells are protected from reactive oxygen species when either superoxide dismutase or catalase is added. When adding an inhibitor specific for photosystem II, diuron, the photocurrent is decreased by 50%.
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| 17. |
- Kanso, Hussein, et al.
(författare)
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Sunlight photocurrent generation from thylakoid membranes on gold nanoparticle modified screen-printed electrodes
- 2018
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 816, s. 259-264
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Tidskriftsartikel (refereegranskat)abstract
- In this work we report on the increase in photocurrent obtained by using thylakoid membranes “wired” with an osmium redox polymer (OsRP) immobilized onto screen-printed carbon and gold electrodes (SPCEs and SPAuEs), modified with gold microparticles (AuMPs) and gold nanoparticles (AuNPs). Both AuMPs and AuNPs were electrodeposited by using the same electrodeposition method in order to study the influence of different electrode surface morphologies, namely AuMPs and AuNPs, on the photocurrent generated when illuminated ΔΔΔ with light with an intensity equivalent to that of sunlight (400 W m−2). AuMPs/SPCEs showed the highest current density (62.5 μA cm−2) upon illumination probably due to a higher capacitive current directly related to the enhanced electroactive area (AEA) and roughness factor (ρ). Finally, the so modified electrodes AuMPs/SPCE and AuNPs/SPAuE were characterized by using scanning electron microscopy (SEM) showing a different surface morphology, resulting in a higher surface roughness for AuMPs/SPCE compared to AuNPs/SPAuE therefore an intimate interaction between the large thylakoid membrane and the AuNPs. A high photocurrent density of 62.5 μA cm−2 was generated at a light intensity of 400 W m−2.
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| 18. |
- Killyeni, Aniko, et al.
(författare)
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Effect of deglycosylation on the mediated electrocatalytic activity of recombinantly expressed Agaricus meleagris pyranose dehydrogenase wired by osmium redox polymer
- 2014
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 126, s. 61-67
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Tidskriftsartikel (refereegranskat)abstract
- The effect of deglycosylation of pyranose dehydrogenase (PDH) obtained from Agaricus meleagris (Am) and recombinantly expressed in Pichia pastoris on its electrocatalytic activity was investigated. Glycosylated (gAmPDH) and deglycosylated PDH (dgAmPDH) were immobilised on spectrographic graphite (G) simultaneously with an osmium redox polymer (Os-RP) using poly(ethylene glycol)(400) diglycidyl ether (PEGDGE) as cross-linking agent. The amperometric response to glucose, recorded at G/(Os-RP)-gAmPDH and G/(Os-RP)-dgAmPDH bioelectrodes, was optimised under flow injection conditions concerning the applied potential, enzyme loading, working pH and flow rate. The G/(Os-RP)dgAmPDH bioelectrode is characterised by better kinetic and electroanalytical parameters compared with the G/(Os-RP)-gAmPDH bioelectrode: (i) a higher value of the maximum catalytic current density, j(max) = (146.6 +/- 2.6) mu A cm(-2) vs. j(max) = (80.9 +/- 1.9) mu A cm(-2); (ii) a lower value of the apparent Michaelis-Menten constant, K-M(app) = (2.4 +/- 0.1) mu M vs. K-M(app) = (7.5 +/- 0.3) mM; (iii) a higher slope of the linear domain, (43.6 +/- 1.1) mu A cm(-2) mM(-1) vs. (9.74 +/- 0.16) mu A cm(-2) mM(-1). Additionally, the time dependent decay of the amperometric response to glucose shows a slightly better operational stability for the G/(Os-RP)-dgAmPDH bioelectrode than that for the G/(Os-RP)-gAmPDH. The enzyme deglycosylation induces significant changes in the order of substrate selectivity for gAmPDH and dgAmPDH. (C) 2013 Elsevier Ltd. All rights reserved.
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| 19. |
- Killyeni, Aniko, et al.
(författare)
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EFFECT OF ENZYME DEGLYCOSYLATION ON THE AMPEROMETRIC DETECTION OF GLUCOSE AT PDH-MODIFIED ELECTRODE
- 2012
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Ingår i: Studia Universitatis Babes-Bolyai, Chemia. - 2065-9520. ; 57:4, s. 87-99
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Tidskriftsartikel (refereegranskat)abstract
- The effect of deglycosylation of pyranose dehydrogenase (PDH), obtained from Agaricus meleagris and recombinantly expressed in Pichia pastoris, on the amperometric detection of glucose was investigated. Glycosylated (gPDH) and deglycosylated (dgPDH) PDH were immobilized on spectrographic graphite (G) simultaneously with an Os redox polymer (Os-RP). The amperometric response of G/Os-RP/gPDH and G/Os-RP/dgPDH to glucose was recorded using flow injection measurements and cyclic voltammetry. A significant increase in the maximum catalytic current density was observed for G/Os-RP/dgPDH [(148.7 +/- 0.14) mu A/cm(2)) compared with G/Os-RP/gPDH [(81.4 +/- 1.4) mu A/cm(2)]. Additionally, the deglycosylation of the enzyme resulted in a higher substrate-enzyme affinity (K-M (app) = 2.44 +/- 0.10 mM), compared with glycosylated PDH (K-M(app) = 7.52 +/- 0.34 mM).
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| 20. |
- Kurbanoglu, Sevinc, et al.
(författare)
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Amperometric Flow Injection Analysis of Glucose and Galactose Based on Engineered Pyranose 2-Oxidases and Osmium Polymers for Biosensor Applications
- 2018
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397. ; 30:7, s. 1496-1504
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, wild type and three mutants of pyranose 2-oxidase (PyOx-WT, PyOx-MT1, PyOx-MT2, PyOx-MT3), which showed improved properties for D-galactose oxidation, were investigated for their oxidising ability when immobilised on graphite electrodes. Four different flexible Os polymers with formal potentials ranging between −0.140 and 0.270 V vs. Ag|AgCl0.1 M KCl were applied together with the various forms of PyOx to wire graphite electrodes using polyethylene glycol diglycidyl ether as crosslinking reagent. The pH profiles for the electrodes modified with wild type and all PyOx mutants in combination with the Os polymers were investigated with both glucose and galactose, respectively, since the PyOx variants showed an improved catalytic activity for galactose. All modified electrodes showed highest response in the pH range between 8.5–10 and KM, Imax values for both glucose and galactose were determined. To prove the catalytic activity, the biosensors were also characterized with cyclic voltammetry. A protein amount 0.26 U was found optimum for PyOx-WT, 0.36 U for PyOx-MT1, 0.41 U for PyOx-MT2 and 0.28 U for PyOx-MT3 and the analytical characterization of the enzyme electrodes was performed for glucose and galactose under optimized conditions.
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| 21. |
- Mateljak, Ivan, et al.
(författare)
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Increasing Redox Potential, Redox Mediator Activity, and Stability in a Fungal Laccase by Computer-Guided Mutagenesis and Directed Evolution
- 2019
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 9:5, s. 4561-4572
-
Tidskriftsartikel (refereegranskat)abstract
- Fungal high-redox-potential laccases (HRPLs) are multi-copper oxidases with a relaxed substrate specificity that is highly dependent on their binding affinity and redox potential of the T1Cu site (E-T1). In this study, we combined computational design with directed evolution to tailor an HRPL variant with increased E-T1 and activity toward high-redox-potential mediators as well as enhanced stability. Laccase mutant libraries were screened in vitro using synthetic highredox-potential mediators with different oxidation routes and chemical natures, while computer-aided evolution experiments were run in parallel to guide benchtop mutagenesis, without compromising protein stability. Through this strategy, the E-T1 of the evolved HRPL increased from 740 to 790 mV, with a concomitant improvement in thermal and acidic pH stability. The kinetic constants for high-redox-potential mediators were markedly improved and were then successfully tested within laccase systems (LMSs). Two hydrophobic substitutions surrounding the T1Cu site appeared to underlie these effects, and they were rationalized at the atomic level. Together, this study represents a proof-of-concept of the joint elevation of the E-T1, redox mediator activity, and stability in an HRPL, making this versatile biocatalyst a promising candidate for future LMS applications and for the development of bioelectrochemical devices.
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| 22. |
- O'Conghaile, Peter, et al.
(författare)
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Fully Enzymatic Membraneless Glucose|Oxygen Fuel Cell That Provides 0.275 mA cm-?2 in 5 mM Glucose, Operates in Human Physiological Solutions, and Powers Transmission of Sensing Data
- 2016
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 88:4, s. 2156-2163
-
Tidskriftsartikel (refereegranskat)abstract
- Coimmobilization of pyranose dehydrogenase as an enzyme catalyst, osmium redox polymers [Os(4,4'-dimethoxy-2,2'-bipyridine)2(poly(vinylimidazole))10Cl]+ or [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl]+ as mediators, and carbon nanotube conductive scaffolds in films on graphite electrodes provides enzyme electrodes for glucose oxidn. The recombinant enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as biocatalysts for glucose oxidn. using flow injection amperometry and voltammetry. In the presence of 5 mM glucose in phosphate-buffered saline (PBS) (50 mM phosphate buffer soln., pH 7.4, with 150 mM NaCl), higher glucose oxidn. current densities, 0.41 mA/cm2, are obtained from enzyme electrodes contg. the deglycosylated form of the enzyme. The optimized glucose-oxidizing anode, prepd. using deglycosylated enzyme coimmobilized with [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl]+ and carbon nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on gold nanoparticle dispersed on gold electrode as a biocathode to provide a membraneless fully enzymic fuel cell. A max. power d. of 275 μW/cm2 is obtained in 5 mM glucose in PBS, the highest to date under these conditions, providing sufficient power to enable wireless transmission of a signal to a data logger. When tested in whole human blood and unstimulated human saliva max. power densities of 73 and 6 μW/cm2 are obtained for the same fuel cell configuration, resp.
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| 23. |
- Pankratov, Dmitry, et al.
(författare)
-
The influence of surface composition of carbon nanotubes on the photobioelectrochemical activity of thylakoid bioanodes mediated by osmium-complex modified redox polymer
- 2019
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 310, s. 20-25
-
Tidskriftsartikel (refereegranskat)abstract
- A combination of photosynthetic biocatalysts with high surface area conductive materials mediated by an osmium-complex modified redox polymer (OsRP)holds promising features for the development of sustainable “green” systems for solar energy conversion. In this work we performed a comparative study of two types of carbon nanotubes (CNTs)synthesized by pyrolysis of polymeric precursors. Both CNTs were of similar morphology, but had a different surface C/O ratio. The CNTs were utilized as a support for immobilization of thylakoid membranes, electrochemically wired through the OsRP. The photobioanodes based on the CNTs with a higher C/O ratio exhibit a higher maximum photocurrent density of 97.1 ± 8.3 μA cm −2 at a light intensity of 400 W m −2 with reduced charge transfer resistance, but had lower operational stability. Our results demonstrate the significance of investigating of electrochemical communication between the photosynthetic component, the redox mediator and the support nanomaterial and may offer new opportunities for designing and optimization of mediated bioelectrochemical systems.
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| 24. |
- Pankratova, Galina, et al.
(författare)
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Electrochemical wiring of the Gram-positive bacterium Enterococcus faecalis with osmium redox polymer modified electrodes
- 2017
-
Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 75, s. 56-59
-
Tidskriftsartikel (refereegranskat)abstract
- The Gram-positive bacterium Enterococcus faecalis was investigated to test its ability to electrochemically communicate with electrodes. E. faecalis cells were successfully “wired” to gold electrodes through [Os(2,2′-bipyridine)2-poly(N-vinylimidazole)10Cl]2 +/+ redox polymer. Maximum current density achieved in response to 10 mM D-glucose was 18 ± 1 μA cm− 2. Control experiments without redox polymer showed no current response. This demonstrates the efficiency of the osmium-based mediator in electron transfer between the cells having a thick cell wall and the electrode. The findings have significant importance in microbial electrochemistry for further understanding of microbe-electrode interactions.
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| 25. |
- Pankratova, Galina, et al.
(författare)
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Electron Transfer between the Gram-Positive Enterococcus faecalis Bacterium and Electrode Surface through Osmium Redox Polymers
- 2019
-
Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 6:1, s. 110-113
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction between microorganisms that contain thick cell walls, such as the Gram-positive bacterium Enterococcus faecalis, and conductive surfaces can be improved by using redox polymers as mediators. Herein, we report a detailed electrochemical characterization of the communication between E. faecalis cells and a series of osmium redox polymers with different redox potentials. The current generated from glucose oxidation by films containing osmium redox polymers and E. faecalis cells increase over time (28h), owing to a decrease in charge-transfer resistance within the films, possibly owing to improved penetration of the redox polymer within the bacterial cell wall.
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| 26. |
- Pankratova, Galina, et al.
(författare)
-
Extracellular Electron Transfer by the Gram-positive Bacterium Enterococcus faecalis
- 2018
-
Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 57, s. 4597-4603
-
Tidskriftsartikel (refereegranskat)abstract
- Extracellular electron transfer (EET) in microbial cells is essential for certain biotechnological applications and contributes to the biogeochemical cycling of elements and syntrophic microbial metabolism in complex natural environments. The Gram-positive lactic acid bacterium Enterococcus faecalis, an opportunistic human pathogen, is shown to be able to transfer electrons generated in fermentation metabolism to electrodes directly and indirectly via mediators. By exploiting E. faecalis wild-type and mutant cells it is demonstrated that reduced demethylmenaquinone in the respiratory chain in the bacterial cytoplasmic membrane is crucial for the EET. Heme-proteins are not involved and cytochrome bd oxidase activity was found to attenuate EET. These results are significant for the mechanistic understanding of EET in bacteria and for design of microbial electrochemical systems. The basic findings infer that in dense microbial communities, such as in biofilm and in the large intestine, metabolism in E. faecalis and similar Gram-positive lactic acid bacteria might be electrically connected to other microbes. Such an intercellular electron transfer might confer syntrophic metabolism that promote growth and other activities of bacteria in the microbiota of humans and animals.
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| 27. |
- Pankratova, Galina, et al.
(författare)
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Supercapacitive Photo-Bioanodes and Biosolar Cells : A Novel Approach for Solar Energy Harnessing
- 2017
-
Ingår i: Advanced Energy Materials. - : John Wiley & Sons. - 1614-6832 .- 1614-6840. ; 7:12
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of supercapacitive photo-bioanode and biosolar cell (photo-biosupercapacitor) for simultaneous solar energy conversion and storage is demonstrated for the first time. Exploiting the capacitive component significantly improves the electron transfer processes and allows the achievement of a current density of 280 µA cm−2 in the pulse mode.
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| 28. |
- Patil, Sunil, et al.
(författare)
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Improved microbial electrocatalysis with osmium polymer modified electrodes.
- 2012
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 48:82, s. 10183-10185
-
Tidskriftsartikel (refereegranskat)abstract
- Using the well-known exoelectrogen Shewanella oneidensis MR-1, an osmium redox polymer modified anode exhibited ca. 4-fold increase in current generation. Additionally, a significant decrease in the start-up time for electrocatalysis was observed. The findings suggest that the inherent extracellular electron transfer capabilities of electrogens coupled with such polymers could enhance electrocatalysis.
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| 29. |
- 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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| 30. |
- Rafighi, Parvin, et al.
(författare)
-
Substrate Preference Pattern of Agaricus meleagris Pyranose Dehydrogenase Evaluated through Bioelectrochemical Flow Injection Amperometry
- 2019
-
Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 6:3, s. 801-809
-
Tidskriftsartikel (refereegranskat)abstract
- Pyranose dehydrogenase (PDH) is a quinone-dependent extracellular flavoglycoprotein mainly produced by litter-decomposing fungi and contributes to the degradation of lignocellulose. PDH in terms of structure and catalytic features pertains to the glucose methanol-choline oxidoreductase family and oxidizes a wide substrate range of aldopyranoses including hexoses, pentoses, disaccharides and oligosaccharides with a high degree of regioselectivity. The purpose of this study was to rationalize the preference of PDH immobilized on an electrode with the structural features of various substrates and thus the kinetic constants were measured for various sugars. PDH was co-immobilized on the electrode with an osmium redox polymer. Response currents for different sugars were measured using flow injection amperometry at +0.3 V vs. Ag|AgCl, KCl (0.1 M). The Michaelis-Menten constants, the turnover numbers and the catalytic efficiency were calculated and revealed that type, orientation and configuration of the substituent play a major role on substrate preference. An OH-group at C-1 and C-6 are not essential and substrate specificities are little affected by the substitution at C-1. The presence and orientation of OH− at C-2 and C-3 are relevant for reactivity. Orientation of OH− at the C-4 position has little effect, and sugars with a substitution below the plane at C-5 are not suitable as substrate. Highest activity for oxidation of glucose, mannose and sucrose was detected at pH 8.5.
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| 31. |
- Shao, Minling, et al.
(författare)
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Optimization of a Membraneless Glucose/Oxygen Enzymatic Fuel Cell Based on a Bioanode with High Coulombic Efficiency and Current Density
- 2013
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 14:10, s. 2260-2269
-
Tidskriftsartikel (refereegranskat)abstract
- After initial testing and optimization of anode biocatalysts, a membraneless glucose/oxygen enzymatic biofuel cell possessing high coulombic efficiency and power output was fabricated and characterized. Agaricus meleagris (AmPDH) and flavodehydrogenase domains of various cellobiose dehydrogenases (DHCDH) were tested during the pre-screening. Myrothecium verrucaria adsorbed on graphite. Optimization showed that the current density for the mixed enzyme electrode could be further improved by using a genetically engineered variant of the non-glycosylated flavodehydrogenase domain of cellobiose dehydrogenase from Corynascus thermophilus expressed in E. coli (ngDH(CtCDHC310Y)) with a high glucose-turnover rate in combination with an Os-complex-modified redox polymer with a high concentration of Os complexes as well as a low-density graphite electrode. AmPDH/ngDH(CtCDHC310Y) anode showed not only a similar maximum voltage as with the biofuel cell based only on the ngDH(CtCDHC310Y) anode (0.55 V) but also a substantially improved maximum power output (20 Wcm(-2)) at 300 mV cell voltage in air-saturated physiological buffer. Most importantly, the estimated half-life of the mixed biofuel cell can reach up to 12 h, which is apparently longer than that of a biofuel cell in which the bioanode is based on only one single enzyme.
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| 32. |
- Tapia, Cristina, et al.
(författare)
-
Wiring of Photosystem I and Hydrogenase on an Electrode for Photoelectrochemical H2 Production by using Redox Polymers for Relatively Positive Onset Potential
- 2017
-
Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 4:1, s. 90-95
-
Tidskriftsartikel (refereegranskat)abstract
- Photosystem I (PSI) is combined with Desulfovibrio gigas hydrogenase for the bioelectrocatalytic photosynthesis of hydrogen at an electrode surface. The activity of these two biocatalysts is linked by two redox polymers; a redox polymer with a relatively positive potential (loaded with an Os complex) is able to reduce PSI and thus facilitates the production of photoexcited electrons, whereas redox polymers of relatively low potential are able to transfer electrons to the hydrogenase. Two negative-potential redox polymers are tested, with either a viologen pendant (4-methyl-4′-bromopropylviologen functionalized linear polyethylenimine) or a cobaltocene pendant (cobaltocene-functionalized branched polyethylenimine, Cc-BPEI). Both are able to protect hydrogenase from O2 inactivation, but only the use of Cc-BPEI yields significant photocurrents for H+ reduction, likely due to its lower redox potential. The photocurrents obtained are found to be proportional to the quantity of H2 produced, reaching a maximum of −30 μA cm−2 for the system incorporating Cc-BPEI and showing a relatively positive onset potential at +0.38 V versus SHE.
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| 33. |
- Tricase, Angelo, et al.
(författare)
-
Water-Based Conductive Ink Formulations for Enzyme-Based Wearable Biosensors
- 2024
-
Ingår i: Advanced Sensor Research. - : Wiley-VCH Verlagsgesellschaft. - 2751-1219. ; 3:3
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, this work reports the first example of second-generation wearable biosensor arrays based on a printed electrode technology involving a water-based graphite ink, for the simultaneous detection of l-lactate and d-glucose. The water-based graphite ink is deposited onto a flexible polyethylene terephthalate sheet, namely stencil-printed graphite (SPG) electrodes, and further modified with [Os(bpy)2(Cl)(PVI)10] as an osmium redox polymer to shuttle the electrons from the redox center of lactate oxidase from Aerococcus viridans (LOx) and gluocose oxidase from Aspergillus niger (GOx). The proposed biosensor array exhibits a limit of detection as low as (9.0 ± 1.0) × 10−6 m for LOx/SPG-[Os(bpy)2(Cl)(PVI)10] and (3.0 ± 0.5) × 10−6 m for GOx/SPG-[Os(bpy)2(Cl)(PVI)10], a sensitivity as high as 1.32 μA mm−1 for LOx/SPG-[Os(bpy)2(Cl)(PVI)10] and 28.4 μA mm−1 for GOx/SPG-[Os(bpy)2(Cl)(PVI)10]. The technology is also selective when tested in buffer and artificial sweat and is endowed with an operational/storage stability of ≈80% of the initial signal retained after 20 days. Finally, the proposed array is integrated in a wristband and successfully tested for the continuous monitoring of l-lactate and d-glucose in a healthy volunteer during daily activity. This is foreseen as a real-time wearable device for sport-medicine and healthcare applications.
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| 34. |
- Yakovleva, Maria, et al.
(författare)
-
Engineering of pyranose dehydrogenase for application to enzymatic anodes in biofuel cells.
- 2015
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:14, s. 9074-9081
-
Tidskriftsartikel (refereegranskat)abstract
- In the search for improved glucose oxidising enzymes for biofuel cells, a number of Agaricus meleagris (Am) pyranose dehydrogenase mutants (mPDHs) exhibiting different degrees of glycosylation were produced using site-directed mutagenesis and electrochemically characterised. The response of electrodes modified with different mPDHs is compared in a mediated electron transfer mode, where the electrodes are modified with each of the mutants covalently attached to redox polymers based on polyvinylimidazole-bound osmium complexes using a cross-linking agent. Coating of each of the enzymes onto the graphite electrode surface is also used to screen for their capacity for direct electron transfer. The double mutant PDH exhibits the highest response to glucose at physiological pH in both direct and mediated electron transfer modes, producing a Jmax of ≈800 μA cm(-2) at room temperature and when "wired" to the Os-polymer having the highest formal potential. From the results obtained the double mPDH is proposed as the most suitable candidate for application to bioanode fabrication.
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| 35. |
- Yakovleva, Maria, et al.
(författare)
-
Further Insights into the Catalytical Properties of Deglycosylated Pyranose Dehydrogenase from Agaricus meleagris Recombinantly Expressed in Pichia pastoris
- 2013
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 85:20, s. 9852-9858
-
Tidskriftsartikel (refereegranskat)abstract
- The present study focuses on fragmented deglycosylated pyranose dehydrogenase (fdgPDH) from Agaricus meleagris recombinantly expressed in Pichia pastoris. Fragmented deglycosylated PDH is formed from the deglycosylated enzyme (dgPDH) when it spontaneously loses a C-terminal fragment when stored in a buffer solution at 4 degrees C. The remaining larger fragment has a molecular weight of similar to 46 kDa and exhibits higher volumetric activity for glucose oxidation compared with the deglycosylated and glycosylated (gPDH) forms of PDH. Flow injection amperometry and cyclic voltammetry were used to assess and compare the catalytic activity of the three investigated forms of PDH, "wired" to graphite electrodes with two different osmium redox polymers: [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(poly(vinylimidazole))(10)Cl](+) [Os(dmbpy)PVI] and [Os(4,4'-dimethoxy-2,2'-bipyridine)(2)(poly-(vinylimidazole))(10)Cl](+) [Os(dmobpy)PVI]. When "wired" with Os(dmbpy)PVI, the graphite electrodes modified with fdgPDH showed a pronounced increase in the current density with J(max). 13- and 6-fold higher than that observed for gPDH- and dgPDH-modified electrodes, making the fragmented enzyme extraordinarily attractive for further biotechnological applications. An easier access of the substrate to the active site and improved communication between the enzyme and mediator matrix are suggested as the two main reasons for the excellent performance of the fdgPDH when compared with that of gPDH and dgPDH. Three of the four glycosites in PDH: N-75, N-175, and N-252 were assigned using mass spectrometry in conjunction with endoglycosidase treatment and tryptic digestion. Determination of the asparagine residues carrying carbohydrate moieties in PDH can serve as a solid background for production of recombinant enzyme lacking glycosylation.
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| 36. |
- Yakovleva, Maria, et al.
(författare)
-
Recombinant pyranose dehydrogenase-A versatile enzyme possessing both mediated and direct electron transfer
- 2012
-
Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 24, s. 120-122
-
Tidskriftsartikel (refereegranskat)abstract
- The catalytical properties of glycosylated pyranose dehydrogenase (gPDH) and deglycosylated PDH (dgPDH) from Agaricus meleagris recombinantly expressed in Pichia pastoris were studied. Both gPDH and dgPDH were "wired" to an osmium redox polymer on graphite electrodes mounted in a flow-injection system. The current from oxidation of glucose by immobilised gPDH and dgPDH was compared using flow injection amperometry and cyclic voltammetry. An increase in the current density was observed for dgPDH (190 mu A cm(-2)) compared with that for gPDH (90 mu A cm(-2)) due to the improved electron transfer between the active site and the electrode. Additionally, the ability of dgPDH for direct electron transfer (DET) was discovered, which is rather unique among FAD-containing enzymes. The ability to oxidise a variety of sugars at a rather low potential makes dgPDH attractive for construction of biofuel cells with high power output. (C) 2012 Elsevier B.V. All rights reserved.
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| 37. |
- Zafar, MNadeem, et al.
(författare)
-
Characterization of different FAD-dependent glucose dehydrogenases for possible use in glucose-based biosensors and biofuel cells.
- 2012
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 402:6, s. 2069-2077
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, different flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) were characterized electrochemically after "wiring" them with an osmium redox polymer [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(PVI)(10)Cl](+) on graphite electrodes. One tested FADGDH was that recently discovered in Glomerella cingulata (GcGDH), another was the recombinant form expressed in Pichia pastoris (rGcGDH), and the third was a commercially available glycosylated enzyme from Aspergillus sp. (AspGDH). The performance of the Os-polymer "wired" GDHs on graphite electrodes was tested with glucose as the substrate. Optimal operational conditions and analytical characteristics like sensitivity, linear ranges and current density of the different FADGDHs were determined. The performance of all three types of FADGDHs was studied at physiological conditions (pH 7.4). The current densities measured at a 20 mM glucose concentration were 494 ± 17, 370 ± 24, and 389 ± 19 μA cm(-2) for GcGDH, rGcGDH, and AspGDH, respectively. The sensitivities towards glucose were 2.16, 1.90, and 1.42 μA mM(-1) for GcGDH, rGcGDH, and AspGDH, respectively. Additionally, deglycosylated rGcGDH (dgrGcGDH) was investigated to see whether the reduced glycosylation would have an effect, e.g., a higher current density, which was indeed found. GcGDH/Os-polymer modified electrodes were also used and investigated for their selectivity for a number of different sugars.
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| 38. |
- Zafar, MNadeem, et al.
(författare)
-
Electron-Transfer Studies with a New Flavin Adenine Dinucleotide Dependent Glucose Dehydrogenase and Osmium Polymers of Different Redox Potentials
- 2012
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 84:1, s. 334-341
-
Tidskriftsartikel (refereegranskat)abstract
- A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris and homogeneously purified, and its glucose-oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os polymers, the redox potentials of which ranged in a broad potential window between +15 and +489 mV versus the normal hydrogen electrode (NHE), were used to immobilize and "wire" GcGDH to the spectrographic graphite electrode's surface. The GcGDH/Os polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis. The current response was investigated using a stepwisely increased applied potential. It was observed that the ratio of GcGDH/Os polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best-suited Os polymer [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(PVI)CI](+) had a potential of +309 mV versus NHE, and the optimum GcGDH/Os polymer ratio was 1:2 yielding a maximum current density of 493,mu A.cm(-2) at a 30 mM glucose concentration.
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| 39. |
- Zafar, MNadeem, et al.
(författare)
-
Wiring of pyranose dehydrogenase with osmium polymers of different redox potentials.
- 2010
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 80, s. 38-42
-
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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