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New strategies for high sensitivity immunoassays.

Bernard, E.J.D.; (2005) New strategies for high sensitivity immunoassays. Doctoral thesis , University of London. Green open access

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Lateral flow immunoassays have large applications in the diagnostic and food industry. A biosensor made of electrostatic self-assembled multilayers of polyphenol oxidase-polyallylamine was studied in order to assess its relevance to a future application in immunoassays. Electrostatic self-assembled multilayers composed only of polyelectrolytes were also investigated to provide a model. This model system allowed understanding the internal properties of this structure. Variations of solution pH and modification of the internal local pH and surface charge density by electrochemistry provided interesting information about the mechanisms involved in multilayer stability to desorption. This stability depends on both multilayers surface charge density and interpenetration of each layer in its neighbouring ones for multilayers with more than nine layers. Enzyme-polyelectrolyte multilayers were more sensible to pH variation as polyallylamine only participated in layer interpenetration. Enzyme activity was also studied by chronoamperometry. Enzymatic kinetics was determined as well as the effect of enzyme activity on multilayer structure. A classic lateral flow sandwich immunoassay (such as a pregnancy test) was studied. A mathematical model describing lateral flow assay was developed and adapted to the studied system. Assay characteristics and properties were described by using different antigen concentrations, flow velocities, particle nature and sizes. Reaction kinetics was determined with the described model. Several factors such as particle size and nature, antibody concentration on the test line, membrane porosity and solution pH were varied in order to optimise signal intensity. Surface treatments of nitrocellulose membrane were also done to enhance the signal. Particle binding on the test line was also investigated to better understand the front edge effect as it is a major problem in lateral flow immunoassays and can involve a wrong signal interpretation.

Type: Thesis (Doctoral)
Title: New strategies for high sensitivity immunoassays.
Identifier: PQ ETD:591895
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1444587
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