Fluorescent semiconductor nanocrystals (“quantum dots”) have several advantages over conventional fluorescent labels, including narrow emission spectra and reduced susceptibility to photobleaching. Because different colors of quantum dots can be excited using a single ultraviolet light source, these new fluors hold great promise for simplifying multicolor biodetection assays. This photograph demonstrates the use of quantum dot labeling in a single-color immunofluorescent assay for detection of Salmonella spp.
A mixed suspension of Salmonella bongori (orange) and Escherichia coli (green) was adhered to a microscope slide treated with 3-aminopropyltriethoxysilane. The surface of the slide was blocked (15 minutes) in buffer containing bovine serum albumin and the cells were reacted (30 minutes) with a biotinylated polyclonal antibody specific for Salmonella spp. (ViroStat, Inc.). Bound antibodies were fluorescently labeled with streptavidin-coated quantum dots emitting at 655 nm (Quantum Dot Corporation), followed by counterstaining with Sytox Green nucleic acid stain (Molecular Probes). The results were viewed using a fluorescence microscope.
Additional background on fluorescent semiconductor nanocrystals (quantum dots) can be found in these references:
Bruchez, M., Jr., M. Moronne, P. Gin, S. Weiss, and A. P. Alivisatos. 1998. Semiconductor nanocrystals as fluorescent biological labels. Science 281:2013-2016.
Chan, W. C. W., D. J. Maxwell, X. Gao, R. E. Bailey, M. Han, and S. Nie. 2002. Luminescent quantum dots for multiplexed biological detection and imaging. Curr. Opin. Biotechnol. 13:40-46.