Renewable Protein A modified graphite-epoxy composite for electrochemical immunosensing

E. Zacco, M. I. Pividori, X. Llopis, M. Del Valle, S. Alegret

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A novel rigid and renewable transducing material for electrochemical immunosensing, based on Protein A bulk-modified graphite-epoxy biocomposite (ProtA-GEB) is reported. Protein A is able to bind to the Fc region of antibodies and provide an affinity matrix for antibody immobilisation onto the transducer. The rigid conducting biocomposite acts not only as a transducer, but also as a reservoir for protein A. After use, the electrode surface can be renewed by a simple polishing procedure, highlighting a clear advantage of this new approach with respect to classical immunoassays. The performance of ProtA-GEB transducers was compared with surface-modified transducers based on a simple dry adsorption procedure, where both Protein A and directly the antibody were adsorbed onto the surface of graphite-epoxy composite (ProtA/GEC and IgG/GEC, respectively). The application of the new biocomposite material in electrochemical immunosensing was studied using a model competitive immunoassay. The immunological reaction was detected using an enzymatic-labeling procedure together with the amperometric detection through a suitable substrate (H 2O2) for the enzyme (HRP). The enzymatic labelling was performed using a two-step procedure based on the biotin/streptavidin interaction as well as a one-step procedure using an antibody labelled with the enzyme. Electrochemical and microscopic characterisation of ProtA-GEB transducer, optimisation of the immunosensor design as well as the stability of this material are also reported. © 2004 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)35-46
JournalJournal of Immunological Methods
Issue number1-2
Publication statusPublished - 1 Mar 2004


  • Biocomposite
  • Electrochemical immunosensor
  • Enzyme label
  • Graphite-epoxy composite
  • Immunoassay
  • Protein A


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