Characterization of Covalently Bound Anti-Human Immunoglobulins on Self-Assembled Monolayer Modified Gold Electrodes

Publication year: 2017
Authors: Holzer B. 1, Manoli K. 1, Ditaranto N. 1,2, Macchia E. 1, Tiwari A. 1, Di Franco C. 3, Scamarcio G. 3,4, Palazzo G. 1,2, Torsi L. 1,2

1 - Dipartimento di Chimica, Università degli Studi di Bari - “Aldo Moro”, Bari, Italy 
2 - CSGI (Center for Colloid and Surface Science) - Bari, Bari, Italy
3 - CNR - Istituto di Fotonica e Nanotecnologie, Sede di Bari, Bari, Italy
4 - Dipartimento di Fisica “M. Merlin” - Università degli Studi di Bari - “Aldo Moro”, Bari, Italy

Published in: Advanced Biosystems, 2017
doi: 10.1002/adbi.201700055

Bioconjugated gold surfaces constitute interesting platforms for biosensing applications. The immobilization of antibodies such as anti-immunoglobulin G and M (anti-IgG and anti-IgM) on gold electrodes via self-assembled monolayers (SAMs) is here studied as a model system for further immunoassays development. The biolayer is characterized by means of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), a dedicated thin-film transistor (TFT)-based platform and electrochemical surface plasmon resonance (EC-SPR). XPS analysis confirms the presence of all the chemical species involved in the fabrication process as well as the covalent attachment of the antibodies with high reproducibility. Visualization of the biolayer topography by AFM shows nanostructures with a thickness consistent with the actual size of the protein, which is also verified by SPR measurements. EC-SPR allows taking advantage of complementary electrochemical and optical signals during the functionalization steps. Moreover, the functionalization of gold leads to a change in the work function, which is demonstrated in an electrolyte gated thin-film transistor configuration. Such configuration enables also to evaluate the electrostatic changes occurring on the gate that are connected with the threshold voltage shifts. The data support that functional biomodified gold surfaces can be reproducibly prepared, which is a prerequisite for further biosensor development.

MP-SPR keywords: amino coupling chemistry, anti-IgG, anti-IgM, antibody immobilization, biosensor, cyclic voltammetry, EC-MP-SPR monitoring of the antibody immobilization, electrochemistry (EC), self-assembly monolayer (SAM), surface coverage, thickness and refractive index (RI) of antibody layer