Magnetic Separation and Centri-Chronoamperometric Detection of Foodborne Bacteria Using Antibiotic-Coated Metallic Nanoparticles

Quality and food safety represent a major stake and growing societal challenge in the world. Bacterial contamination of food and water resources is an element that pushes scientists to develop new means for the rapid and efficient detection and identification of these pathogens. Conventional detection tools are often bulky, laborious, expensive to buy, and, above all, require an analysis time of a few hours to several days. The interest in developing new, simple, rapid, and nonlaborious bacteriological diagnostic methods is therefore increasingly important for scientists, industry, and regulatory bodies. In this study, antibiotic-functionalized metallic nanoparticles were used to isolate and identify the foodborne bacterial strains Bacillus cereus and Shigella flexneri. With this aim, a new diagnostic tool for the rapid detection of foodborne pathogenic bacteria, gold nanoparticle-based centri-chronoamperometry, has been developed. Vancomycin was first stabilized at the surface of gold nanoparticles and then incubated with the bacteria B. cereus or S. flexneri to form the AuNP@vancomycin/bacteria complex. This complex was separated by centrifugation, then treated with hydrochloric acid and placed at the surface of a carbon microelectrode. The gold nanoparticles of the formed complex catalyzed the hydrogen reduction reaction, and the generated current was used as an analytical signal. Our results show the possibility of the simple and rapid detection of the S. flexneri and B. cereus strains at very low numbers of 3 cells/mL and 12 cells/mL, respectively. On the other hand, vancomycin-capped magnetic beads were easily synthesized and then used to separate the bacteria from the culture medium. The results show that vancomycin at the surface of these metallic nanoparticles is able to interact with the bacteria membrane and then used to separate the bacteria and to purify an inoculated medium.