A microfluidic biosensor for rapid detection of Salmonella typhimurium based on magnetic separation, enzymatic catalysis and electrochemical impedance analysis

Rapid screening of foodborne pathogens is of great significance to ensure food safety. A microfluidic biosensor based on immunomagnetic separation, enzyme catalysis and electrochemical impedance analysis was developed for rapid and sensitive detection of S. typhimurium. First, the bacterial sample, the magnetic nanoparticles (MNPs) modified with capture antibodies, and the enzymatic probes modified with detection antibodies and glucose oxidase (GOx) were simultaneously injected into the microfluidic chip, followed by mixing and incubation to form MNP-bacteria-probe sandwich complexes. Then, glucose with high impedance was injected into the chip and catalyzed by the GOx on the complexes into hydrogen peroxide with high impedance and gluconic acid with low impedance, which was finally measured using the low-cost interdigitated microelectrode and the electrochemical impedance analyzer to determine the target bacteria. Under the optimal conditions, this biosensor could quantitatively detect S. typhimurium at the concentrations from 1.6 × 102 CFU/mL to 1.6 × 106 CFU/mL in 1 h with the low detection limit of 73 CFU/mL. Besides, this biosensor was demonstrated with good feasibility for practical applications by detecting the S. typhimurium spiked chicken meat samples.