In-situ immuno-gold nanoparticle network ELISA biosensors for pathogen detection

• Development of novel gold nanoparticle network biosensors for diagnostics.
• Direct detection possible in food matrices because of a magnetic separation step.
• Detection of less than 10 CFU/ml of the foodborne pathogens possible in food matrices in less than 2 h.
• Enhancement of signal can be controlled to increase sensitivity.
• Can be generalized to detect a variety of threat agents for biosecirity.

Food poisoning microorganisms that contaminate food products and compromise food safety and security have been considered a major health threat and a serious concern for food producers and processors. Developing sensor technologies that are rapid for sensitive and selective detection and quantification of pathogens is a high priority for scientists in academia, state and federal research institutes, and industries. In this work we propose an in-situ immuno-AuNP network-based ELISA biosensor integrated with a sample concentration step based on immuno-magnetic separation to detect pathogenic microorganisms with high sensitivity. The sensor system was optimized by the specific formation of immuno-AuNP network onto the antigenic site present at the outer membrane surface of bacteria and the analytical concept was validated by a microtiter immunoassay. The in-situ network biosensor was able to detect pathogens at extremely low numbers: 3 cells/mL of Escherichia coli O157:H7 and Salmonella typhimurium in buffer and 3 CFU/mL of E. coli O157:H7 and 15 CFU/mL of S. typhimurium in real sample conditions within 2 h of inoculation. The ability to monitor target bacteria with improved analytical sensitivity compared to the current techniques presents a unique opportunity for routine monitoring to improve the safety of foods.