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Aspects on mediated glucose oxidation at a supported cubic phase
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.ORCID iD: 0000-0001-8261-8098
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2017 (English)In: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 118, p. 8-13Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 118, p. 8-13
Keywords [en]
Enzymatic biofuel cells, Lipid cubic phase, Liquid-crystal, Monoolein, Glucose oxidase, Ferrocene-carboxylic acid
National Category
Materials Chemistry Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-130584DOI: 10.1016/j.bioelechem.2017.06.010ISI: 000412258800002PubMedID: 28672274Scopus ID: 2-s2.0-85021421161OAI: oai:DiVA.org:umu-130584DiVA, id: diva2:1068157
Note

Originally included in thesis in manuscript form.

Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2023-03-23Bibliographically approved
In thesis
1. Electrochemical investigations on lipid cubic phases
Open this publication in new window or tab >>Electrochemical investigations on lipid cubic phases
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electrochemical Impedance Spectroscopy (EIS) was used to develop a novel methodology for studying ionic interaction with lipids arranged in a lipid cubic phase (LCP). Studying different types of ions, both cations and anions, validated the method. A free-standing LCP membrane was formed between two cell compartments and impedance experiments were carried out in a 2-electrode setup to estimate dielectric properties of the membrane, exposed to the following electrolyte solutions at different concentrations: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptophan. Two different LCP were used in this setup, i.e: Monoloein/water and the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/H2O). SAXRD measurements were performed to determine the space group of the cubic phase and confirm the stability of the LCP during measurements.

Membrane resistances and capacitances were found from equivalent circuit fitting to the impedance data. The membrane resistance was shown to be related to ionic interaction with the lipid head group in the water channels of the LCP. Membrane capacitance were correlating to condensing and swelling effect of LCP due to the exposure of ions. The results correlated well with the SAXRD results and earlier published data.

The results also indicate that these membranes become less permeable to ions as they increase in size as well as in charge or polarity. 

Cyclic voltammetry was used to study the applications of a LCP for modification of the bioanode in a biofuel cell. The monoolein cubic phase was used to host Glucose oxidase (GOx) and a freely diffusing ferrocene carboxylate was used as mediator. The supported cubic phase had an intrinsic resistance in the same order of magnitude as the freestanding MO-LCP membrane as measured with EIS.

Abstract [sv]

Elektrokemisk impedans spektroskopi har använts för att utveckla en ny metod för att studera joners växelverkan med lipider som bildat en kubisk fas. Olika typer av joner, både positiva och negativa, användes för att validera metoden. Ett fristående membran uppbyggt av en kubisk fas separerade två avdelningar i en elektrokemisk cell. Cellen fylldes med elektrolyt-lösningar och impedansmätningar kunde utföras mellan två platina elektroder placerade i vardera avdelning. Membranet exponerades för följande elektrolytlösningar av olika koncentration: KCl, CsBr, CaCl2, MgCl2, CsCl, NaCl, NaOAc and NaTryptofan. Två olika kubiska faser användes i denna uppställning, dvs: Monoloein/vatten och det ternära systemet monoolein/dioleoylfosfatidylkolin/vatten(MO/DOPC/H2O). Med hjälp av SAXRD kunde den kubiska fasens kristallstruktur bestämmas och dess stabilitet under mätningarna bekräftas. De dielektriska egenskaperna hos membranet bestämdes genom att anpassa impedansspektrat till en ekvivalent krets bestående av resistanser, kapacitanser och konstant-faselement. Membranresistansen visade sig vara relaterad till jonernas växelverkan med lipidhuvudgruppen i vattenkanalerna i kubiska fasen. Ju starkare växelverkan desto högre var resistansen. Membrankapacitansen kunde korreleras med kondenserande och uppsvällande effekter på kubiska fasen förorsakade av exponeringen till joner. Resultaten bekräftades av SAXRD mätningar och även tidigare publicerade data. Resultaten indikerar också tydligt att permeabiliteten hos membranet minskar med ökad jonstorlek, jonladdningoch polaritet hos jonen. Cyklisk voltammetri användes för att studera en tillämpning av kubiska fasen i en tänkt applikation som bioanod i en biobränslecell. Elektroden modifierades med en kubisk fas innehållande GOx och tillsammans med en fritt diffunderande ferrocen karboxylat som mediator, där oxidation av glukos studeras. Det visade sig att den kubiska fasen hade en resistans av samma storleksordning som det fristående membranet uppmätt med impedansspektroskopi.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2017. p. 46
Keywords
Monoolein, Electrochemical Impedance Spectroscopy, lipid cubic phase, ionic interaction, biofuel cell
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-130174 (URN)978-91-7601-660-2 (ISBN)
Public defence
2017-02-08, Stora hörsalen KBE303, KBC-huset, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2017-01-25 Created: 2017-01-13 Last updated: 2018-06-09Bibliographically approved

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