This technology takes advantages of the high sensitivity of quantum dot fluorescence measurement and the high efficiency of immunomagnetic separation. The detection limit for Escherichia coli O157:H7 is 10³ cells/mL (Figures 5 and 6), which is lower than that of the conventional dye-based method by at least 100 times.

Figure 5. Typical fluorescence emission spectra (after subtracting the blank) obtained for detection E. coli O157:H7.

Figure 6. Fluorescence intensity as a function of the concentration of E. coli O157:H7.

X.-L. Su, Y. Li. 2004. Quantum dot biolabeling coupled with immunomagnetic separation for detection of Escherichia coli O157:H7, Anal. Chem. 76 (16), 4806-4810.

L. Yang, Y. Li. 2005. Quantum dots as fluorescent labels for quantitative detection of Salmonella Typhimurium in chicken carcass wash water. J. Food. Prot. (in press).