Detection of ESAT-6 by a label free miniature immuno-electrochemical biosensor as a diagnostic tool for tuberculosis

•Development of a miniature electrochemical biosensor to detect the virulent factor of Mycobacterium tuberculosis, ESAT-6.•The developed immunosensor presents high sensitivity and specificity toward ESAT-6.•Anti-ESAT-6 immunosensor specifically recognizes the native ESAT-6 in CFP from pathogenic strains of Mtb.•Anti-ESAT-6 immunosensor is proposed as a potential efficient tool to diagnose Tuberculosis.

Tuberculosis is a worldwide disease considered as a major health problem with high morbidity and mortality rates. Poor detection of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis remains a major obstacle to the global control of this disease. Here we report the development of a new test based on the detection of the major virulent factor of Mtb, namely the early secreted antigenic target 6-kDa protein or ESAT-6. A label free electrochemical immunosensor using an anti-ESAT-6 monoclonal antibody as a bio-receptor is described herein. Anti-ESAT-6 antibodies were first covalently immobilized on the surface of a gold screen-printed electrode functionalized via a self-assembled thiol monolayer. Interaction between the bio-receptor and ESAT-6 antigen was evaluated by square wave voltammetry method using [Fe(CN)6]3 −/4 − as redox probe. The detection limit of ESAT-6 antigen was 7 ng/ml. The immunosensor has also been able to detect native ESAT-6 antigen secreted in cell culture filtrates of three pathogenic strains of Mtb (CDC1551, H37RV and H8N8). Overall, this work describes an immune-electrochemical biosensor, based on ESAT-6 antigen detection, as a useful diagnostic tool for tuberculosis.

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