In this paper, a low-cost, simple, and highly sensitive electrochemical immunosensor was fabricated for the tetracycline detection based on gold electrode-modified carboxyl-Fe3O4 nanoparticle (MNPs) by chitosan (CS) as linker. The anti-tetracycline monoclonal antibody (Ab) was immobilized on the modified electrode surface. The binding of tetracycline to Ab was analyzed by differential pulse voltammetry. Here, MNPs were used as the signal amplifier to improve the sensitivity of the immunosensor. The stepwise assembly process of the electrochemic...