Organic–Inorganic Core–Shell Satellite Nanostructures for Dual-Readout Detection of <i>Escherichia coli</i> O157:H7

Foodborne pathogenic <i>Escherichia coli</i> O157:H7 (<i>E. coli</i> O157:H7) can threaten human health and cause socioeconomic burdens. Consequently, it is imperative to establish a method for rapidly and sensitively detecting <i>E. coli</i> O157:H7. Herein, we developed a dual-readout lateral flow immunoassay (LFIA) platform based on a core-shell structure (Y6NPs@Au) with excellent colorimetric and photothermal performances. Benefiting from the excellent near-infrared absorption capability of the Y6 molecule, a large number of Y6 molecules were loaded into polystyrene microspheres to obtain nanoparticles (Y6NPs) with outstanding photothermal performance. Subsequently, gold nanoparticles (AuNPs) were modified on the surface of Y6NPs by the polyethylenimine-mediated electrostatic interaction, which was conducive to improving the colorimetric and photothermal performances significantly, as well as antibody coupling efficiency. The obtained Y6NPs@Au has a high molar extinction coefficient at 525 nm (1.603 × 10¹² M^-1 cm^-1) and photothermal conversion efficiency (49.76%). Especially, the limits of detection (LODs) of the established Y6NPs@Au-LFIA for the detection of <i>E. coli</i> O157:H7 were 1725 CFU mL^-1 in colorimetric mode and 311 CFU mL^-1 in photothermal mode, which were 2.88- and 2.93-fold lower than that of Y6NPs-LFIA with a colorimetric LOD of 4969 CFU mL^-1 and a photothermal LOD of 912 CFU mL^-1. Moreover, the Y6NPs@Au-PT-LFIA exhibited a wider linear range than the Y6NPs@Au-CM-LFIA. Additionally, the recovery rates for detecting <i>E. coli</i> O157:H7 were 83.4-114.1% in municipal water and food samples based on Y6NPs@Au-LFIA. Overall, this study demonstrates that Y6NPs@Au with excellent performances as a signal reporter is promising in improving the detection performance of the LFIA platform.