Magnetic Prussian blue nanoparticles to enhance dual-readout lateral flow immunoassay for Salmonella typhimurium detection

Background Traditional immunochromatographic assay (ICA) test strips typically utilize colloidal gold nanoparticles as colorimetric signal reporters, but they often suffer from compromised sensitivity and quantitative accuracy, making them inadequate for the stringent demands of trace-level screening. In addition, the heterogeneous nature of food matrices, such as dairy products, meat, and ready-to-eat fruits and vegetables, complicates the accuracy and reliability of ICA for detecting foodborne pathogens. Therefore, enhancing the detection accuracy of ICA is critical to meet the stringent requirements for pathogen detection in complex food samples. Results Here, we synthesized a novel Prussian blue-coated Fe 3 O 4 nanoparticle (Fe 3 O 4 @PB) via a simple in-situ growth method. The synthesized Fe 3 O 4 @PB nanoparticles demonstrate a high magnetization strength and excellent photothermal conversion efficiency, enabling their application as efficient probes in ICA. Leveraging these properties, we developed a dual-readout ICA incorporating both colorimetric and photothermal modalities for the sensitive detection of Salmonella typhimurium in milk and lettuce samples. The detection limit (LOD) for Fe 3 O 4 @PB-ICA reached 2.5 × 10 3  CFU/mL in colorimetric formats and 1.04 × 10 3  CFU/mL in photothermal formats, representing approximately 4-fold and 10-fold improvements compared to AuNP-ICA (LOD = 1 × 10 4  CFU/mL). Furthermore, the average recovery rates ranged from 89.1 % to 111.9 %, while the coefficients of variation below 13.7 %, demonstrating excellent accuracy and precision. Significance The proposed Fe 3 O 4 @PB serves as effective probe for purifying and enriching target analytes, significantly improving the accuracy and sensitivity of colorimetric and photothermal immunochromatographic analysis applications. By leveraging the magnetic and photothermal capabilities of Fe 3 O 4 @PB, the developed Fe 3 O 4 @PB-ICA represents a promising rapid diagnostic platform for the sensitive detection of foodborne pathogens and other analytes.