Hybrid Electrochemical/Magnetic Assay for Salmonella Typhimurium Detection

Electrochemical immunoassay involving two magnetic steps-separation of unbound nanoparticles from bacteria/antigen-Fe₃O₄ nanoparticles conjugates and concentrating of the conjugates on solid substrate is proposed. Carbon screen printed electrodes covered antibodies specific to Salmonella typhimurium (strain SL 7207) serves as the mentioned substrate. Immunocomplex formed is being solved in the mixture of acids (0.36 M H₂SO₄ and 0.28 M HNO₃) is analyzed for Fe³⁺ concentration. The last is determined by stripping voltammetric method. It provides information on quantity of conjugates localized on the substrate and the last one is proportional to the pathogen concentration in the analyte. Detection limit is for Salmonella typhimurium 8.18 CFU/ml and for antigen Salmonella typhimurium 1.51 × 10^-7 mg/ml (1.51 CFU/ml).