Label-free electrochemical immunosensor based on electrodeposited Prussian blue and gold nanoparticles for sensitive detection of citrus bacterial canker disease

A novel label free electrochemical immunosensor was developed for rapid and direct detection of the effector protein PthA, for citrus canker diagnosis. The immunosensor fabrication was based on the sequential electrodeposition of Prussian blue (PB) and gold nanoparticles (GNPs) on the surface of bamboo-like multiwall carbon nanotubes-ionic liquid nanocomposite (BCNT-IL) modified glassy carbon electrode. The morphology of the modified electrode surface was studied by means of field emission scanning electron microscope (FE-SEM). Moreover, the role of each component in the modified electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that the used modification strategy effectively enhanced the stability and electroactivity of the PB as electron mediator. After immobilization of the anti-PthA antibody and blocking with BSA, the immunosensor was used for determination of different concentrations of PthA antigen under the optimal conditions. The linear dynamic range of fabricated immunosensor was from 0.1 to 50 nM with a detection limit of 0.028 nM. The proposed immunosensor exhibited high selectivity, long-term stability and good reproducibility. Moreover, good results were obtained for the determination of PthA in real samples, indicating the great potential of the developed immunosensor for detection of citrus canker disease.