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Novel reagentless electrodes for biosensing
Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Analytical chemical information is needed in all areas of human activity including health care, pharmacology, food control and environmental chemistry. Today one of the main challenges in analytical chemistry is the development of methods to perform accurate and sensitive rapid analysis and monitoring of analytes in ‘real’ samples. Electrochemical biosensors are ideally suited for these applications.

Despite the wide application of electrochemical biosensors, they have some limitations. Thus, there is a demand on improvement of biosensor performance together with a necessity of simplification required for their mass production. In this thesis the work is focused on the development of electrochemical sensors with improved performance applicable for mass production, e.g. by screen printing.

Biosensors using immobilized oxidases as the bio-recognition element are among the most widely used electrochemical devices. Electrical communication between redox enzymes and electrodes can be established by using natural or synthetic electron carriers as mediators. However, sensors based on soluble electronshuttling redox couples have low operational stability due to the leakage of water-soluble mediators to the solution. We have found a new hydrophobic mediator for oxidases – unsubstituted phenothiazine. Phenothiazine and glucose oxidase, lactate oxidase or cholesterol oxidase were successfully co-immobilized in a sol-gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively. All elaborated biosensors with phenothiazine as a mediator exhibited long-term operational stability. A kinetic study of the mediator has shown that phenothiazine is able to function as an efficient mediator in oxidase-based biosensors.

To improve sensitivity of the biosensors and simplify their production we have developed a simple approach for production of graphite microelectrode arrays. Arrays of microband electrodes were produced by screen printing followed by scissor cutting, which enabled the realization of microband arrays at the cut edge. The analytical performance of the system is illustrated by the detection of ascorbic acid through direct oxidation and by detection of glucose using a phenothiazine mediated glucose biosensor. Both systems showed enhanced sensitivity due to improved mass transport. Moreover, the developed approach can be adapted to automated electrode recovery.

Finally, two enzyme-based electrocatalytic systems with oxidation and reduction responses, respectively, have been combined into a fuel cell generating a current as an analytical output (a so-called self-powered biosensor). This was possible as a result of the development of the phenothiazine mediated enzyme electrodes, which enabled the  construction of a cholesterol biosensor with self-powered configuration. The biosensor generates a current when analyte (cholesterol) is added to the cell. The biosensor has been applied for whole plasma analysis.

All developed concepts in the thesis are compatible with a wide range of applications and some of them may even be possible to realize in a fully integrated biosensor unit based on printed electronics.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 53 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1689
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-112345DOI: 10.3384/lic.diva-112345ISBN: 978-91-7519-187-4 (print)OAI: oai:DiVA.org:liu-112345DiVA: diva2:765553
Presentation
2014-11-28, Shrödinger, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-11-03Bibliographically approved
List of papers
1. 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
2. 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
3. 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
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

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