Efficient separation and quantitative detection of Listeria monocytogenes based on screen-printed interdigitated electrode, urease and magnetic nanoparticles

Rapid screening of pathogenic bacteria contaminated foods is the key to prevent and control the outbreaks of foodborne illness. In this study, an impedance biosensor was developed using immunomagnetic nanoparticles for efficient separation and concentration of the Listeria monocytogenes cells, urease for amplifying the weak signal, and screen-printed interdigitated electrode for quantitative measurement of the impedance change of the catalysate. The magnetic nanoparticles (MNPs) coated by the monoclonal antibodies (MAbs) were used to separate the Listeria cells from the background and concentrate them in small volume of PBS. Then, the gold nanoparticles (GNPs) modified with the urease and the polyclonal antibodies (PAbs) were used to react with Listeria to form the MNP-Listeria-GNP sandwich complexes. The complexes were re-suspended with the urea to catalyze the hydrolysis of the urea into ammonium ions and carbonate ions, which were measured by the electrode. A new equivalent circuit was designed for simulation of the biosensor with a good fitting result. Under the optimized conditions, a linear relationship between the impedance changes and the concentrations of Listeria from 1.9 x 10(3) to 1.9 x 10(6) CFU/mL was obtained. The limit of detection of this biosensor was 1.6 x 10(3) CFU/mL and the recovery of the spiked lettuce sample ranges from 94.7% to 103.8%. This proposed biosensor was developed at much lower cost than our previous studies and could be more applicable for in-field detection of foodborne pathogens. (C) 2016 Elsevier Ltd. All rights reserved.