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Facilitating electron transfer in bioelectrocatalytic systems
Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bioelectrocatalytic systems are based on biological entities, such as enzymes, whole cells, parts of cells or tissues, which catalyse electrochemical processes that involve the interaction between chemical change and electrical energy. In all cases, biocatalysis is implemented by enzymes, isolated or residing inside cells or part of cells. Electron transfer (ET) phenomena, within the protein molecules and between biological redox systems and electronics, enable the development of various bioelectrocatalytic systems, which can be used both for fundamental investigations of enzymatic biological processes by electrochemical methods and for applied purposes, such as power generation, bioremediation, chemical synthesis and biosensing.

Electrical communication between the biocatalyst’s redox centre and an electrode is essential for the functioning of the system. This can be established using two main mechanisms: indirect ET and direct ET. The efficiency of the ET influences important parameters such as the turnover rate of the biocatalyst, the generated current density and partially the stability of the system, which in their turn determine response time, sensitivity, detection limit and operational stability of biosensing devices or the power densities and current output of biofuel cells, and hence should be carefully considered when designing bioelectrocatalytic systems.

This thesis focuses on approaches that facilitate ET in bioelectrocatalytic systems based on indirect and direct ET mechanisms. Both fundamental aspects of ET in bioelectrocatalytic systems and applications of such systems for biosensing and power generation are considered. First, a new hydrophobic mediator for oxidases – unsubstituted phenothiazine and its improved ET properties in comparison with commonly used mediators are discussed. Application of the mediator in electrochemical biosensors is demonstrated by glucose, lactate and cholesterol sensing. Utilisation of mediated biocatalytic cholesterol oxidation, as the anodic reaction for the construction of a biofuel cell acting as a power supply and an analytical device at the same time, is investigated to deliver a selfpowered biosensor. Also the enhancement of mediated bioelectrocatalysis by employment of microelectrodes as a transducer is examined. The effect of surface roughness on the current response of the microelectrodes under conditions of convergent diffusion is considered. The applicability of the laccase-based system for total phenol analysis of weakly supported water is demonstrated. Finally, a new electrochemical approach derived from collision-based electrochemistry applicable for examination of the ET process of a single enzyme molecule is described.

All together, the results presented in this thesis contribute to the solution of the ‘electronic coupling problem’, arising when interfacing biomolecules with electronics and limiting the performance of bioelectrocatalytic systems in specific applications. The developed methods to facilitate ET will hopefully promote future biosensing devices and biofuel cells. I believe the new approach for investigation of ET processes at a single enzyme molecule will complement existing single molecule techniques, giving further insights into enzymatic ET mechanisms at the molecular level and filling the gap between fundamental understanding of biocatalytic processes and their potential for bioenergy production.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1738
National Category
Chemical Sciences Chemical Engineering Chemical Process Engineering
Identifiers
URN: urn:nbn:se:liu:diva-125242DOI: 10.3384/diss.diva-125242ISBN: 978-91-7685-841-7 (print)OAI: oai:DiVA.org:liu-125242DiVA: diva2:903875
Public defence
2016-03-18, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2017-11-03Bibliographically approved
List of papers
1. Bioelectrocatalytic systems for health applications
Open this publication in new window or tab >>Bioelectrocatalytic systems for health applications
2016 (English)In: Biotechnology Advances, ISSN 0734-9750, E-ISSN 1873-1899, Vol. 34, no 3, 177-197 p.Article, review/survey (Refereed) Published
Abstract [en]

We present a brief overview of bioelectrocatalytic devices for in vitro health applications, including food safety and environmental analysis, focusing on microelectrode- and microfluidic-based biosensors, paper-based point-of-care devices and wearable biosensors. The main hurdles and future perspectives are discussed. We then consider the role of electron transfer between a biocatalyst and an electrode in biosensor design. Brief descriptions of indirect, direct and mediated mechanisms are given. The principal strategies, as well as recent developments for modulation of electron transfer in biocatalytic systems are summarised. In conclusion, we highlight some of the challenges associated with improving these redox systems.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Direct electron transfer; Mediated electron transfer; Immobilisation; Microbiosensor; Nanobiosensor; Paper-based biosensor; Wearable biosensor; Self-powered biosensor
National Category
Bioinformatics and Systems Biology
Identifiers
urn:nbn:se:liu:diva-123688 (URN)10.1016/j.biotechadv.2015.12.005 (DOI)000375500700004 ()26724183 (PubMedID)
Available from: 2016-01-08 Created: 2016-01-08 Last updated: 2017-12-01Bibliographically approved
2. Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
Open this publication in new window or tab >>Reagentless Biosensor Based on Glucose Oxidase Wired by the Mediator Freely Diffusing in Enzyme Containing Membrane
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2012 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 3, 1220-1223 p.Article in journal (Refereed) Published
Abstract [en]

Wiring glucose oxidase in the membrane with an immobilized mediator is possible due to the diffusion ability of the latter, if the enzyme containing membrane is formed according to the proposed protocol, including exposing proteins to water–organic mixtures with the high content of organic solvent. In the course of the study, the new glucose oxidase mediator, unsubstituted phenothiazine, was discovered. The diffusion coefficient of the mediator in the resulting membrane is independent of the presence of enzyme. The cyclic voltammograms of the enzyme electrode after appearance of the only glucose in solution obtain a well-defined catalytic shape, which is normally observed for both the enzyme and the mediator in solution. Analytical performances of the resulting biosensor are comparable to the advanced second generation ones, which, however, require covalent linking of the mediator either to the membrane forming polymer or to the enzyme. Even without such covalent linking, the reported biosensor is characterized by an appropriate long-term operational stability allowing reagentless sensing.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2012
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-112343 (URN)10.1021/ac203056m (DOI)22206508 (PubMedID)
Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-12-05Bibliographically approved
3. Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
Open this publication in new window or tab >>Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
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2014 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 53, 275-282 p.Article in journal (Refereed) Published
Abstract [en]

The mediation of oxidases glucose oxidase (GOx), lactate oxidase (LOx) and cholesterol oxidase (ChOx) by a new electron shuttling mediator, unsubstituted phenothiazine (PTZ), was studied. Cyclic voltammetry and rotating-disk electrode measurements in nonaqueous media were used to determine the diffusion characteristics of the mediator and the kinetics of its reaction with GOx, giving a second-order rate constant of 7.6×103–2.1×104 M−1 s−1 for water–acetonitrile solutions containing 5–15% water. These values are in the range reported for commonly used azine-type mediators, indicating that PTZ is able to function as an efficient mediator. PTZ and GOx, LOx and ChOx were successfully co-immobilised in sol–gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively, which were then optimised in terms of stability and sensitivity. The electrocatalytic oxidation responses showed a dependence on substrate concentration ranging from 0.6 to 32 mM for glucose, from 19 to 565 mM for lactate and from 0.015 to 1.0 mM for cholesterol detection. Oxidation of substrates on the surface of electrodes modified with PTZ and enzyme membrane was investigated with double-step chronoamperometry and the results showed that the PTZ displays excellent electrochemical catalytic activities even when immobilised on the surface of the electrode.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Phenothiazine; Electron transfer mediator; Enzyme biosensor; Glucose oxidase; Lactate oxidase; Cholesterol oxidase
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-100391 (URN)10.1016/j.bios.2013.09.071 (DOI)000329881100044 ()
Available from: 2013-11-05 Created: 2013-11-05 Last updated: 2017-12-06Bibliographically approved
4. Cholesterol Self-Powered Biosensor
Open this publication in new window or tab >>Cholesterol Self-Powered Biosensor
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2014 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 19, 9540-9547 p.Article in journal (Refereed) Published
Abstract [en]

Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilized in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalyzed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M-1 cm(-2)), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol. Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.

Place, publisher, year, edition, pages
American Chemical Society, 2014
National Category
Physical Sciences Biological Sciences
Identifiers
urn:nbn:se:liu:diva-112176 (URN)10.1021/ac501699p (DOI)000343017100031 ()25164485 (PubMedID)
Note

Funding Agencies|Swedish research council Formas; research centre Security Link; Swedish Institute

Available from: 2014-11-18 Created: 2014-11-18 Last updated: 2017-12-05
5. Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
Open this publication in new window or tab >>Arrays of Screen-Printed Graphite Microband Electrodes as a Versatile Electroanalysis Platform
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2014 (English)In: ChemElectroChem, ISSN 2196-0216, Vol. 1, no 4, 755-762 p.Article in journal (Refereed) Published
Abstract [en]

Arrays of microband electrodes were developed by screen printing followed by cutting, which enabled the realization of microband arrays at the cut edge. The microband arrays of different designs were characterized by physical and electro-chemical methods. In both cases, the methods showed that the microband width was around 5 mm. Semi-steady-state cyclic voltammetry responses were observed for redox probes, and chronocoulometric measurements showed the establishment of convergent diffusion regimes characterized by current densities similar to those of a single microelectrode. The analytical performance of the electrode system and its versatility were illustrated with two electrochemical assays: detection of ascorbic acid through direct oxidation and a mediated glucose biosensor fabricated by dip coating. Due to convergent mass transport, both systems showed an enhancement in their analytical characteristics. The developed approach can be adapted to automated electrode recovery.

Place, publisher, year, edition, pages
Wiley, 2014
Keyword
graphite screen printing; microarrays; microband; sensors; voltammetry
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-109289 (URN)10.1002/celc.201300204 (DOI)000338296100010 ()
Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2017-11-03Bibliographically approved
6. Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currents
Open this publication in new window or tab >>Evaluation of the electrochemically active surface area of microelectrodes by capacitive and faradaic currents
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Two methods to estimate the electrochemically active surface area (EASA) of microelectrodes were compared. One is based on electrocapacitive measurements and the other on faradaic measuements. A systematic study revealed a strong influence of the surface roughness and the electrolyte concentration on the EASA of microelectrodes estimated from the electrocapacitive measurements, yielding a lack of reliability compared to the faradaic method.

Keyword
Electrochemically active surface area, microelectrode, microband, roughness, capacitive process, faradaic process
National Category
Chemical Sciences Chemical Engineering Chemical Process Engineering
Identifiers
urn:nbn:se:liu:diva-125240 (URN)
Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2017-11-03Bibliographically approved
7. Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
Open this publication in new window or tab >>Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
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2016 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 907, 45-53 p.Article in journal (Refereed) Published
Abstract [en]

The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M−1 cm−2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Laccase; microelectrode; microband; electrochemical modeling; total phenol analysis; wastewater
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-123677 (URN)10.1016/j.aca.2015.12.006 (DOI)000368422900005 ()
Note

Funding agencies: Swedish research council Formas [245-2010-1062]; research centre Security Link [VINNOVA 2009-00966]; Norrkopings fond for Forskning och Utveckling; VINNOVA

Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2017-12-01Bibliographically approved
8. Electrocatalytic Currents from Single Enzyme Molecules
Open this publication in new window or tab >>Electrocatalytic Currents from Single Enzyme Molecules
2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 8, 2504-2507 p.Article in journal (Refereed) Published
Abstract [en]

Single molecule enzymology provides an opportunity to examine details of enzyme mechanisms that are not distinguishable in biomolecule ensemble studies. Here we report, for the first time, detection of the current produced in an electrocatalytic reaction by a single redox enzyme molecule when it collides with an ultramicroelectrode. The catalytic process provides amplification of the current from electron-transfer events at the catalyst leading to a measurable current. This new methodology monitors turnover of a single enzyme molecule. The methodology might complement existing single molecule techniques, giving further insights into enzymatic mechanisms and filling the gap between fundamental understanding of biocatalytic processes and their potential for bioenergy production.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Chemical Sciences Chemical Engineering Chemical Process Engineering
Identifiers
urn:nbn:se:liu:diva-125241 (URN)10.1021/Jacs.5b13149 (DOI)000371453700011 ()
Note

Funding agencies:  Swedish research council Formas [245-2010-1062]; research center Security Link (VINNOVA ) [2009-00966]; Centre in Nano Science and Technology (CeNano, Linkoping University)

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Available from: 2016-02-17 Created: 2016-02-17 Last updated: 2017-11-30Bibliographically approved

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