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Title: Optimised label-free biomarker assays with electrochemical impedance spectroscopy
Author: Xu, Mengyun
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2013
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There is huge academic interest and clinical need associated with the development of biomarker immunoassays where general aims are the generation of highly specific, convenient and sensitive sensing formats. In this project, a powerful electrochemical technique, electrochemical impedance spectroscopy (EIS), is applied in the establishment of powerful biomarker detecting protocols. Firstly, ultrasensitive, label-free and reusable insulin sensors, based on an antibody-PEGylated thiol self-assembly monolayer (PEG thiol SAM) interface, were produced and characterised via Faradaic EIS, presenting a detection limit (LOD) of 1.2 pM, a linear range across four orders of magnitude, and high sensitivity in even 50 % serum. By applying similar surface chemistry, a label-free biosensor, specific for the detection of α-synuclein antibodies, was fabricated. The α-synuclein interfaces used enabled the reliable detecting of this biomarker in patient sample serum. The concentration levels in the control and a patient group were determined to be significantly different, and, significantly, this difference was consistently across two different cohorts. Strikingly, this could potentially underpin an entirely new means of early Parkinson’s disease (PD) diagnosis. Non-Faradaic EIS methods were additionally applied to label-free insulin assays at both PEG thiol SAM and zwitterionic polymer film interfaces. The latter presented not only an exceptionally non-fouling interface, but also one seemingly both highly biocompatible and facilitating enhanced receptor: target binding. Finally, impedance assays, though potent, generally, operate by sampling only one of a limited number of available experimental variables, typically, Rct for Faradaic EIS, or C or Z for non-Faradaic EIS. Work carried out herein also explores the generation and utility of a portfolio of mathematically derived immittance functions all obtained from the same raw data sets. A particular focus was the examination of whether these were capable of increasing assay sensitivity and efficiency above normal impedance treatments.
Supervisor: Davis, Jason Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biochemistry ; Immunodiagnostics ; Electrochemical Impedance Spectroscopy (EIS) ; Immunoassays ; Diabetes ; Parkinson's Disease