A novel label-free electrochemical immunosensor modified by glutathione and hyaluronic acid for the ultrasensitive and ultraselective detection of brucellosis in dilute serum

Due to the serious harm of brucellosis to society and economy and the lack of effective vaccine associated with it, the early rapid detection of this disease is still the most effective mean to prevent it. Here, a specific antigen of brucellosis, the outer membrane protein 31 (OMP31), was prepared, identified and purified. Based on this newly-prepared antigen, a label-free and low-fouling electrochemical immunosensor of brucellosis detection in buffer, especially in dilute serum samples was successfully constructed. Au nanoparticles (AuNPs) were first electrodeposited onto the glass carbon electrode through i-t technique and a complex matrix was then formed by the covalent attachment of glutathione (GSH) and hyaluronic acid (HA) onto gold surface one by one for the subsequent modification of OMP31. Finally the prepared electrochemical immunosensors were characterized using Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Under optimized conditions, a linear concentration range from 2.08 × 10−15 g mL −1 to 1.04 × 10−12 g mL−1 and a low detection limit (LOD) of 0.50 fg mL−1 (S/N = 3) that is lower than that of most of the existing methods were exhibited, indicating its feasible commercial value in practical detection.