An integrated colorimetric and photothermal lateral flow immunoassay based on bimetallic Ag-Au urchin-like hollow structures for the sensitive detection of E. coli O157:H7.

Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as the signal reporter is widely used for the rapid detection of food-borne pathogens. However, it is difficult for LFIA to achieve sensitive detection due to the insufficient colorimetric signal brightness of AuNPs. Herein, we developed a bimetallic Ag-Au urchin-like hollow nanospheres (BUHNPs) based on the simple and rapid synthesis through co-reduction and galvanic replacement reactions. The BUHNPs exhibit superb colorimetric signal brightness, strong photothermal signals and high antibody coupling efficiency. The obtained colorimetric and photothermal LFIA (BUHNPs-CM-LFIA and BUHNPs-PT-LFIA) based on BUHNPs were used for the sensitive detection of a pathogenic bacterium (Escherichia coli O157:H7). The limit of detection values of the colorimetric and photothermal quantitative analysis were 2.48 × 10 and 5.50 × 10 CFU mL, which were approximately 4-fold and 18-fold lower than that of AuNPs-LFIA (9.92 × 10 CFU mL), respectively. This work suggests that a dual-readout LFIA with BUHNPs as a promising signal reporter can be used to improve the detection performance of LFIA and construct a more accurate and sensitive detection platform.