Label-free electrochemical immunosensor for direct detection of Citrus tristeza virus using modified gold electrode

This paper presents the first label-free and sensitive electrochemical immunosensor for efficient and rapid detection of Citrus tristeza virus (CTV). The specific antibody against coat protein (CP) of CTV was successfully immobilized on 11-mercaptoundecanoic acid (MUA) and 3-mercapto propionic acid (MPA) modified gold electrode via carbodiimide coupling reaction using N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride (EDC) and N-HydroxySuccinamide (NHS). Electrochemical characterizations of the immunosensor (anti-CTV/MUA-MPA/Au electrode) were carried out by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical detection was performed by differential pulse voltammetry in [Fe(CN)6]3−/4− solution. The decrease in the [Fe(CN)6]3−/4− current upon increasing antigen concentrations on the immunosensor surface was determined in the range of 1 nM to 5 μM. The developed immunosensor provided a much lower limit of detection (LOD = 0.27 nM) than ELISA and other reported immunoassay techniques for CTV detection. The specificity of the immunosensor was also examined and no significant interference from other analytes in the real sample was observed. The proposed immunosensor is simple, relatively inexpensive, and shows good sensitivity for this application.