Drinking water contamination and food poisoning caused by bacterial pathogens are urgent issues plaguing today's world. One possible route to detect these organisms is based on the photophysical properties of CdSe nanocrystals (NCs), which exhibit size-tunable fluorescence that spans the visible spectrum. Their narrow emission spectra, broad absorption spectra, and high photostability versus traditional organic fluorophores make these materials attractive for biological applications. The development of a selective colorimetric label for Escherichia coli O157:H7 cells is based on the binding of biotinylated anti-E. coli O157:H7 antibodies and avidin-functionalized CdSe/ZnS core/shell NCs. This system is advantageous, since it allows for the targeting of other bacterial species simply by using different antibodies.
