Foodborne pathogens primarily refer to pathogenic bacteria that use food as a transmission vehicle. These pathogens can survive in food or water sources, and after consumption, may lead to intestinal diseases or food poisoning, potentially resulting in death in severe cases. Common foodborne pathogens include Bacillus cereus, Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella, Campylobacter jejuni, Listeria monocytogenes, and Escherichia coli. Traditional culture-based methods are currently the gold standard for bacterial detection, being both inexpensive and accurate, but are limited by their labor-intensive, time-consuming, and low-throughput nature. In recent years, many technologies have been developed for rapid and sensitive detection of pathogens, with nucleic acid-based detection and immunoassays being the most commonly used. However, nucleic acid methods based on polymerase chain reaction (PCR) typically require expensive equipment and trained operators. Traditional enzyme-linked immunosorbent assay (ELISA) is time-consuming and relatively low in sensitivity.

Currently, nanostructures (NS), including gold nanoparticles (AuNPs), MnO2, gold nanorods (AuNRs), and polydopamine (PDA), have been used for specific identification and inactivation of pathogens. Gold nanoparticles (AuNPs) have attracted great interest in the development of rapid and visual sensors due to their simple synthesis, easy surface modification, and good biocompatibility. These nanoparticles possess unique surface plasmon resonance, exhibiting red or purple colors corresponding to their dispersed or aggregated states. Furthermore, several studies have demonstrated that AuNPs have significant near-infrared absorption capabilities, enabling them to convert light energy into thermal energy, making them promising candidates for targeted photothermal therapy.

In this study, we propose a novel colorimetric biosensor. First, we screened three phage-derived bacterial-binding proteins (PBPs) that specifically bind to Escherichia coli, Salmonella, and Staphylococcus aureus, namely the T3 phage tail fiber protein (TFP), Salmonella phage CKT1 tailspike protein (TSP), and Staphylococcus aureus phage plyV12 endolysin cell wall binding domain (CBD). By combining PBPs with gold nanoparticles, we developed a "detect and kill" biosensor, AuNPs@PBP, for direct detection and subsequent inactivation of three foodborne pathogens. The aggregation of AuNPs@PBP on the surface of foodborne pathogens causes a color change in the detection system, which is then analyzed based on red-green-blue (RGB) values, directly generating bacterial concentration values on a mobile app. The detection results are conveniently displayed on a smartphone application, enabling rapid and sensitive detection of pathogens within 30 minutes, which has broad application prospects in fields such as food and environmental monitoring.