Electrochemical impedance spectroscopy and surface plasmon resonance for diagnostic antibody detection

[摘要] The successful use of biomarker antibody detection for disease diagnosis is currentlyrestricted to cases where the antibody affinity and specificity of interaction withantigen 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 theprinciple that these technologies allow the measurement of antibody binding toimmobilized antigen, i.e. without the need to wash away excess, non-boundantibodies or using labelled antibodies. Proof of principle for this in the case ofdetection of biomarker anti-mycolic acid antibodies for TB diagnosis has beenprovided in the Mycolic acid Antibody Real-Time Inhibition assay (MARTI) by ourresearch group. Although already patented and published, MARTI is not yet a feasiblediagnostic test due to slow sample turn-around time, affordability and technicalvulnerability associated with unstable lipid antigen surface chemistry and thedifficulty of standardization of liposome carriers of mycolic acids used for measuringthe binding inhibition of serum antibodies to immobilized antigen. Here, thesechallenges were addressed by investigating the use of a magnetic field for more stablelipid antigen immobilization, new phospholipid compositions to generate more stableliposome 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-aroundtime. The latter approach appeared quite promising in distinguishing a TB positiveand a TB negative patient serum and is amenable to automation by means of a flowinjection system.

[发布机构] University of Pretoria