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Electrochemical measurement of antibody­‐antigen recognition biophysics: thermodynamics and kinetics of human chorionic gonadotropin (hCG) binding to redox-­tagged antibodies

Partington, Lee I; Atkin, Stephen L; Kilpatrick, Eric S; Morris, Samuel H; Piper, Mark; Lawrence, Nathan S; Wadhawan, Jay D

Authors

Lee I Partington

Stephen L Atkin

Eric S Kilpatrick

Samuel H Morris

Mark Piper

Nathan S Lawrence



Abstract

The thermodynamics and kinetics of antigen binding under diffusive conditions to an electrode surface modified with ferrocene-tagged antibodies is studied within this work, and realised experimentally for the case of human chorionic gonadotropin (hGC) as the antigen with monoclonal anti-hCG antibodies immobilised on an electrode surface via a molecular wire platform. The formation of the antigen-antibody complex is monitored through the blocking of the ferrocene voltammetry, thereby enabling the fractional coverage of the electrode binding sites to be unravelled as a function of time. It is found that, at low antigen concentrations, a Frumkin adsorption isotherm fits the data, with repulsive interactions between bound antigens playing a significant rôle, with an affinity constant that is two orders of magnitude larger than in the case of an untagged antibody, suggesting that the chemical hydrophobicity of the redox tag may encourage stronger binding. Comparison of the experimental temporal data with relevant diffusion-adsorption models under activation control allows for the extraction of the kinetic parameters; at zero coverage, the rate constants for adsorption and desorption are, respectively, larger and smaller than the untagged antibody. The kinetic study enables the confirmation that this type of platform may be utilised for rapid (15 min) and quantitative electroimmunoassay. This is validated through proof-of-concept analytical measurements, yielding a limit of detection around 25 mIU mL-1 (corresponding to 2.7 ngmL-1) – a value used clinically for urine hCG measurements corresponding to around four weeks of gestational age.

Journal Article Type Article
Publication Date Jun 15, 2018
Print ISSN 1572-6657
Electronic ISSN 1873-2569
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 819
Pages 533-541
APA6 Citation Partington, L. I., Atkin, S. L., Kilpatrick, E. S., Morris, S. H., Piper, M., Lawrence, N. S., & Wadhawan, J. D. (2018). Electrochemical measurement of antibody­‐antigen recognition biophysics: thermodynamics and kinetics of human chorionic gonadotropin (hCG) binding to redox-­tagged antibodies. Journal of Electroanalytical Chemistry, 819, 533-541. https://doi.org/10.1016/j.jelechem.2018.02.062
DOI https://doi.org/10.1016/j.jelechem.2018.02.062
Keywords Electroimmunoassay; Frumkin isotherm; Partially blocked electrodes; Molecular wire; Chemoreception biophysics
Publisher URL https://www.sciencedirect.com/science/article/pii/S1572665718301590
Copyright Statement ©2018, Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Copyright Statement
©2018, Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/







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