Impedimetric immunosensor for the label-free and direct detection of botulinum neurotoxin serotype A using Au nanoparticles/graphene-chitosan composite

In this work, a novel nanocomposite film consisting of the Au nanoparticles/graphene-chitosan has been designed to construct an impedimetric immunosensor for a rapid and sensitive immunoassay of botulinum neurotoxin A (BoNT/A). BoNT/A antibody was immobilized on glassy carbon electrode modified with Au nanoparticles/graphene-chitosan for the signal amplification. The fabrication of immunosensor was extensively characterized by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The impedance changes, due to the specific immuno-interactions at the immunosensor surface that efficiently restricted the electron transfer of redox probe Fe(CN)64−/3− were utilized to detect BoNT/A. The measurements were highly targeted specific and linear with logarithmic BoNT/A concentrations in PBS, milk and human serum across a 0.27-268 pg mL−1 range and associated with a detection limit of 0.11 pg mL−1.