Rapid Immunosensing of Salmonella Typhimurium Using Electrochemical Impedance Spectroscopy: the Effect of Sample Treatment

A label‐free immunosensor for rapid detection of Salmonella Typhimurium based on electrochemical impedance spectroscopy was developed. Specific antibody was immobilized to a screen‐printed electrode via cysteamine monolayer activated with glutaraldehyde and the impedance was measured between two gold electrodes. Different procedures for sample treatment (combinations of heat and sonication) were tested and their impact on the assay performance was compared. Atomic force microscopy was used to study the effect of the treatment on the cell shape and to confirm the specific binding of Salmonella to the sensing surface. The immunosensor allowed detection of 1×103 CFU ⋅ mL−1 in 20 min with negligible interference from other bacteria. Wide linear response was obtained in the range between 103 CFU ⋅ mL−1 and 108 CFU ⋅ mL−1. The successful detection of Salmonella in spiked milk demonstrates the suitability of sensor for the analysis of real samples.