Sensitive detection of Escherichia coli O157:H7 and Salmonella typhimurium in food samples using two-channel fluorescence lateral flow assay with liquid Si@quantum dot.

Here, we proposed a silica-quantum dot (QD)-based fluorescent lateral flow immunoassay (LFA) method with high sensitivity for the simultaneous qualification of Salmonella typhimurium and Escherichia coli O157:H7 in food samples. The silica-QD nanobead (Si@DQD) with dual-QD shell was introduced into the two-channel LFA strip as the advanced fluorescent tag, thus providing superior fluorescence signal, monodispersity, and excellent stability for actual sample detection. The liquid Si@DQD tags were mixed with sample solution and directly loaded onto the LFA strip for the quantitative analysis of target bacteria within 15 min. The detection limit of the proposed assay reached 50 cells/mL for both S. typhi/E. coli and was approximately 200 times more sensitive than the colloidal gold (AuNP)-based LFA strips. The Si@DQD-LFA also exhibited the advantages of good stability, specificity, and easy operation, suggesting its great potential for real bacterial sample detection.