A simple quantum dot-based fluoroimmunoassay method for selective capturing and rapid detection of Salmonella Enteritidis on eggs

The aim of this paper was to demonstrate a rapid and selective fluorescence-linked immunoassay method based on quantum dots as the fluorescent marker for the detection of Salmonella Enteritidis on eggshell. Highly-fluorescent and water-soluble CdTe quantum dots were prepared by using thioglycolic acid and 1-thioglycerol as ligands and were then conjugated with anti-Salmonella antibodies. As a result of specific interaction, Salmonella Enteritidis were specifically captured by bioconjugated CdTe quantum dots which led to the detection of a fluorescent signal. The bacterial cell images were obtained using fluorescence microscopy. Under optimal conditions, the quenched fluorescence intensity increased linearly with the log total count of Salmonella Enteritidis ranging from 3 × 102 to 3 × 107 CFU/mL within 1-2 h. The low detection limit was 1 × 102 CFU/mL without sample enrichment. This method was satisfactorily applied to the analysis of egg samples, which was demonstrated as a simple scheme for quick and selective detection of Salmonella Enteritidis on eggshell.