Polydopamine-coated two-dimensional nanomaterials as high-affinity photothermal signal tag towards dual-signal detection of Salmonella typhimurium by lateral flow immunoassay

Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters has been extensively utilized for the rapid detection of foodborne pathogens. Nevertheless, it’s challenging for LFIA to obtain sensitive detection, because of the inefficient coupling of AuNPs and antibodies and the poor colorimetric signals. To improve on this, we used a two-dimensional nanomaterial (Cu2MoS4) modified with PDA (CMS@PDA) that provides superior bio-affinity and excellent photothermal signal qualities. With the CMS@PDA material, we successfully constructed a portable LFIA device for specific detection of Salmonella typhimurium (S. typhimurium) using a dual-signal probe that combines colorimetric and photothermal signals (CM/PT). The dynamic detection range of the CMS@PDA-LFIA is 103 to 107 cfu mL−1. Notably, the detection limit of 103 cfu mL−1 is 100 times more sensitive compared to AuNPs-based LFIA. Moreover, the assay exhibits satisfactory recovery rates for S. typhimurium detection in food samples. In this research, the coating of PDA solves the problem of low water-solubility of CMS, making the proposed CMS@PDA nanocomposite showcase better performance in the CM/PT mode detection by LFIA. Beyond all doubt, this work offers a novel supplement for applying multifunctional two-dimensional nanomaterials in LFIAs.