A fluorescent strategy for Escherichia coli detection in raw beef in combination with click chemistry

Foodborne bacterial infections are a growing concern for the public. The development of a rapid, economical and sensitive method for foodborne bacteria detection remains a paramount challenge. In this study, Escherichia coli (E. coli) bacteria-assisted click chemistry brings borophene quantum dots (B QDs) at the close proximity of Fe₃O₄@Au NPs that enabled magnetic separation as well as quantification of E. Coli in the presence of cupric ion (Cu^2 +). At first, azide-modified B QDs and alkyne-modified gold coated iron oxide nanoparticles (Fe₃O₄@Au NPs) was synthesized through wet-chemical method. The size of Fe₃O₄@Au NPs and B QDs was 80 nm and ∼3 nm, respectively. The absorbance peak of the Fe₃O₄@Au NPs and the emission peak of B QDs were located at 540 nm and 530 nm, respectively. E. Coli bacterial metabolic product cuprous ion (Cu⁺) was utilized to trigger the click reaction between B QDs and Fe₃O₄@Au NPs. As a result, a self-assembled structure of B QDs and Fe₃O₄@Au NPs formed which enables magnetic separation and fluorescent quantification of E. coli. The calculated limits of detection (LODs) of E. coli in PBS and spiked raw meat samples were 3 colony-forming unit (CFU)/mL and 20 CFU/mL, respectively. The present E. coli assay was selective in the presence of other bacteria.