A novel method based on fluorescent magnetic nanobeads for rapid detection of Escherichia coli O157:H7.

Fluorescent lateral flow immunoassay (FLFIA) based on immunomagnetic separation (IMS) has the advantage of sensitivity. However, its complex operation includes IMS, elution, incubation, and FLFIA steps. Here, we prepared a core@shell@satellite structure fluorescent magnetic nanobeads (FMNBs) and firstly introduced them into the novel method that integrated IMS with FLFIA (I-IMS-FLFIA) for the detection of Escherichia coli O157:H7. The FMNBs exhibited excellent magnetic and fluorescent properties for applications in IMS and FLFIA. However, the inner filter effect (IFE) of FMNBs may disturb the detection of I-IMS-FLFIA. Systematical studies showed that the amount of immuno-FMNBs and the concentration of monoclonal antibody can be controlled to obtain maximum photoluminescence intensity and effectively weaken or solve IFE. Under optimum conditions, this method allows for the quantified detection of 2.39 × 102 CFU/mL and qualified detection of 2.50 × 103 CFU/mL. The method is simple, safe, efficient, and sensitive for the detection of foodborne pathogens.