Biosensors 2016, 6(3), 43; https://doi.org/10.3390/bios6030043
Effects of Surface Epitope Coverage on the Sensitivity of Displacement Assays that Employ Modified Nanoparticles: Using Bisphenol A as a Model Analyte
Yang Lu 1
, Joshua Richard Peterson 2, Erwann Luais 2, John Justin Gooding 3,*
and Nanju Alice Lee 4,*
, Joshua Richard Peterson 2, Erwann Luais 2, John Justin Gooding 3,*
and Nanju Alice Lee 4,*
1
School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
2
School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
3
School of Chemistry and Australian Centre for NanoMedicine, University of New South Wales, Sydney, NSW 2052, Australia
4
School of Chemical Engineering and ARC Training Centre for Advanced Technologies in Food Manufacture, University of New South Wales, Sydney, NSW 2052, Australia
*
Authors to whom correspondence should be addressed.
Academic Editor: Luigi Campanella
Received: 17 June 2016 / Revised: 21 July 2016 / Accepted: 29 July 2016 / Published: 8 August 2016
(This article belongs to the Special Issue Next-Generation Immunosensors)
Abstract
With the ever-increasing use of nanoparticles in immunosensors, a fundamental study on the effect of epitope density is presented herein, with a small molecule epitope, on the performance of the displacement assay format in an enzyme-linked immunosorbent assay (ELISA). Thiolated bisphenol A (BPA) functionalized gold nanoparticles (cysBPAv-AuNPs) and specific anti-BPA antibodies are employed for this purpose. It is shown that the displacement of cysBPAv-AuNPs bound to the immobilized antibodies was influenced by both the avidity of bound cysBPAv-AuNPs and the concentration of free BPA to displace it. The importance of surface epitope density was that it changed the number of epitopes in close proximity to the antibody-binding site. This then influenced the avidity of cysBPAv-AuNPs bound to the immobilized antibody. Furthermore, the molar epitope concentration in an assay appears to affect the degree of antibody binding site saturation. Controlling surface epitope density of the functionalized nanoparticles and molar epitope concentration in an assay leads to a decrease of the concentration of free BPA required to displace the bound cysBPAv-AuNP, and hence better assay performance with regards to the D50 value and dynamic range in the displacement assay. View Full-Text
Graphical abstract
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Lu, Y.; Peterson, J.R.; Luais, E.; Gooding, J.J.; Lee, N.A. Effects of Surface Epitope Coverage on the Sensitivity of Displacement Assays that Employ Modified Nanoparticles: Using Bisphenol A as a Model Analyte. Biosensors 2016, 6, 43.
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