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Title: A study of enzyme monolayers immobilised on electrode surfaces
Author: Singhal, Kavita
ISNI:       0000 0001 3416 0166
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1997
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The enzyme glucose oxidase (GOx) was used throughout this study. An investigation into the electrostatic interactions of GOx with polycatonic redox polymers was conducted. It was shown that GOx forms an electrostatic complex with an osmium redox polymer which strongly absorbs to a glassy carbon electrode. Control of the solution pH and ionic strength allowed the stability and magnitude of the catalytic response to be optimised. It was demonstrated that monolayer deposition results in a larger catalytic response with respect to the amount of immobilised material when compared with other techniques employing similar materials. A more complex structure was constructed on thiol modified gold. Monolayers of GOx and a ferrocene redox polymer were alternately deposited and immobilised through electrostatic attraction. The catalytic response and number of ferrocence sites present increased with the number of layers deposited. GOx has a stabilising effect on the oxidised forms of the redox polymer sites but overall decreases the rate of charge transfer within the film. The scanning electrochemical microscope (SECM) was found to be an effective means of imaging enzyme modified surfaces. A monolayer of GOx was immobilised in poly(phenol) on Pt and variations in the activity of GOx in the presence of glucose studied. It was shown that through the detection of hydrogen peroxide, oxygen or other solution mediator, such as ferrocene monocarboxylic acid, variations in GOx activity were detectable over the surface. From the images obtained it was concluded that a significant proportion of GOx is immobilised with the active site uncovered above the poly(phenol) film. A brief study of aspartic acid derivatives of tetrathiafulvalene (TTF) suggests that the attachment of an amino acid to TTF does not affect the overall electrochemical characteristics. The formation of oligomeric units results in unusual variations in the voltammetry when compared to that of unmodified TTF, this may be attributed to the occurrence of a reorganisation step of the larger oligomers after the first oxidation step.
Supervisor: Denuault, Guy ; Bartlett, Philip Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biosensor design