Electron transfer dynamics across self-assembled N-(2-mercaptoethyl) octadecanamide/mycolic acid layers: impedimetric insights into the structural integrity and interaction with anti-mycolic acid antibodies

Kenneth I. Ozoemena, Nsovo S. Mathebula, Jeseelan Pillay, Gianna Toschi, Jan A. Verschoor
2010 Physical Chemistry, Chemical Physics - PCCP  
The integrity and properties of mycolic acid (MA) antigens integrated into a self-assembled monolayer (SAM) of N-(2-mercaptoethyl)octadecanamide, (MEODA), on a gold electrode have been interrogated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS data showed that Au-MEODA and Au-MEODA-MA behave as microelectrode arrays, with pinholes acting as the microelectrodes that permit electron transport between a redox-active probe in solution and the underlying gold
more » ... face. The average radii of the pinholes (r a ) and half the distance between the centers of the neighbouring pinholes (r b ), were estimated from EIS using the pore size model, and discussed. Anti-MA antibodies present in a tuberculosis (TB)-infected patient (co-infected with HIV) strongly interact with Au-MEODA-MA showing a rather compact and stable bio-complex structure that is virtually defect-free. The electrochemical impedimetric properties associated with the ability of the Au-MEODA-MA to discriminate between TB positive and negative human sera are also discussed. We prove that the Au-MEODA and Au-MEODA-MA electrodes, as well as the MA-anti-MA antibody interactions, are characterized with time-constant dispersion, typical of microstructures with grain/grain boundary phases. These crucial physico-electrochemical insights into the behaviour of surface-confined MA should provide a useful basis for the design and development of a potential impedimetric immunosensing platform for active tuberculosis.
doi:10.1039/b915930d pmid:20023812 fatcat:vsmpeocwx5corgtt2rvzsjvzne