Electrochemical impedance spectroscopy and surface plasmon resonance for diagnostic antibody detection

Abstract

The successful use of biomarker antibody detection for disease diagnosis is currently restricted to cases where the antibody affinity and specificity of interaction with antigen is high. Evanescent field biosensing, e.g. Surface Plasmon Resonance (SPR), and electrochemical detection, in particular Electrochemical Impedance Spectroscopy (EIS), have been shown viable for detection of lower affinity antibodies, based on the principle that these technologies allow the measurement of antibody binding to immobilized antigen, i.e. without the need to wash away excess, non-bound antibodies or using labelled antibodies. Proof of principle for this in the case of detection of biomarker anti-mycolic acid antibodies for TB diagnosis has been provided in the Mycolic acid Antibody Real-Time Inhibition assay (MARTI) by our research group. Although already patented and published, MARTI is not yet a feasible diagnostic test due to slow sample turn-around time, affordability and technical vulnerability associated with unstable lipid antigen surface chemistry and the difficulty of standardization of liposome carriers of mycolic acids used for measuring the binding inhibition of serum antibodies to immobilized antigen. Here, these challenges were addressed by investigating the use of a magnetic field for more stable lipid antigen immobilization, new phospholipid compositions to generate more stable liposome carriers for lipid antigen in solution and the use of screen-printed electrodes (SPE) in EIS to address affordability of diagnosis and improve sample turn-around time. The latter approach appeared quite promising in distinguishing a TB positive and a TB negative patient serum and is amenable to automation by means of a flow injection system.