Analytical and Bioanalytical Chemistry

, Volume 405, Issue 11, pp 3889–3898 | Cite as

The impact of antibody/epitope affinity strength on the sensitivity of electrochemical immunosensors for detecting small molecules

  • Sook Mei Khor
  • Pall Thordarson
  • J. Justin Gooding
Original Paper


A displacement immunoassay involves having a labelled analogue of the analyte (the epitope) already bound to the antibody. The presence of the analyte causes a competition for antibodies, and some of the antibodies dissociates from the epitope so that it can bind with the analyte. Herein, the influence of the affinity of the surface-bound epitope for the antibody on the sensitivity and selectivity of a displacement immunosensor is explored both theoretically and experimentally. An electrochemical immunosensor described previously [1], where the dissociation of antibodies from an electrode surface causes an increase in current from surface-bound ferrocene species, is used for this purpose. As expected, the ease and effectiveness of the bound antibody being displaced is inversely related to the affinity of the antibody to the surface-bound epitope relative to the analyte in solution as expected. However, if the affinity constant is too low, selectivity and/or sensitivity are compromised. Experimental results are qualitatively compared with a simple mass-action model.


The important parameters in displacement immunoassays are investigated theoretically via a simple mass action model and compared with experimental data generated using a novel electrochemical immunosensor, as shown, where antibody on the surface suppresses electrochemistry and, hence, displacement of the antibody increases the current


Immunosensor Displacement assay Theory Electrochemistry 



This research was supported under the Australian Research Council Linkage projects funding scheme (LP100200593).

Supplementary material

216_2013_6782_MOESM1_ESM.pdf (224 kb)
ESM 1 (PDF 223 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Sook Mei Khor
    • 1
    • 2
  • Pall Thordarson
    • 1
  • J. Justin Gooding
    • 1
  1. 1.School of Chemistry and Australian Centre for NanoMedicineThe University of New South WalesSydneyAustralia
  2. 2.Department of Chemistry, Faculty of ScienceUniversity of MalayaKuala LumpurMalaysia

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