A streamlined lateral flow immunoassay for <i>S. typhimurium</i> using intrinsically multifunctional magnetic nanoprobes for capture, enrichment, and signal amplification

<i>Salmonella typhimurium</i> (<i>S. typhimurium</i>) is a major foodborne pathogen, posing significant public health risks and leading to substantial economic losses. Traditional lateral flow immunoassay (LFIA) technology for foodborne pathogen detection faces limitations, such as the challenging and costly process of screening paired antibodies. To address these issues, we developed an innovative label-free LFIA utilizing carboxyl-functionalized Fe₃O₄ nanoparticles for sensitive detection of <i>S. typhimurium</i>. Fe₃O₄ nanoparticles offer unique properties, including magnetic separation and peroxidase-like catalytic activity, which enhance both bacterial capture and colorimetric signal amplification. The proposed label-free magnetic separation LFIA (LFMS-LFIA) achieved a detection limit of 10³ cfu mL^-1 for <i>S. typhimurium</i> using catalytic signal amplification, with a sensitivity 10 times greater than that achieved with colorimetric signal alone. This approach demonstrates promising application potential in <i>S. typhimurium</i> contamination detection in samples such as drinking water, eggs, and skim milk. By utilizing probes that integrate efficient binding, magnetic enrichment, and signal amplification capabilities, this Fe₃O₄-enhanced LFIA represents a major advancement in <i>S. typhimurium</i> detection with high sensitivity and without the need for complex equipment. This work offers a cost-effective and highly sensitive solution in portable devices of food safety and environmental monitoring fields for the on-site detection of pathogens.