A sensitive assay based on specific aptamer binding for the detection of Salmonella enterica serovar Typhimurium in milk samples by microchip capillary electrophoresis

The detection of Salmonella enterica serovar Typhimurium (S. Typhimurium) is very important for the prevention of food poisoning and other infectious diseases. Here we reported a simple and sensitive strategy to test S. Typhimurium by microchip capillary electrophoresis couple with laser-induced fluorescence (MCE-LIF) based on the specific reaction between the bacterium and corresponding aptamers. Based on the differences in charge to mass ratio between bacteria-aptamer complexes and free aptamers, a separation of the complexes and free aptamers could be obtained by MCE. The optimal parameters of the specific reaction including fluorescent dye concentration, Mg²⁺ concentration, incubation time, and pH of incubation solution were carefully investigated. Meanwhile, a non-specific DNA was exploited as a contrast for the detection of S. Typhimurium. Under the optimal conditions, a rapid separation of the bacteria-aptamer complex and free aptamers was achieved within 135 s with a limit of detection (S/N = 3) of 3.37 × 10² CFU mL⁻¹. This method was applied for the detection of S. Typhimurium in fresh milk samples and a recovery rate of 95.8% was obtained. The experimental results indicated that the specific aptamers are of enough biostability and the established method could be used to analyze S. Typhimurium in foods.