Fluorescent semiconductor nanocrystals in microscopy and flow cytometry

Quantum dots nanocrystals (Qdots or QDs), consisting of a CdSe core with a ZnS shell, are a novel class of fluorochromes with significant advantages over traditional organic fluorochromes and fluorescent proteins. QDs have a large extinction coefficient, high photostability, wide absorption and narrow emission spectra, and large Stokes shifts. These features make them desirable for both microscopy and flow cytometry. Applications of QD-conjugates with antibodies, streptavidin, and DNA or RNA probes have made it possible to produce highly stable multicolor specimens useful for scientific and diagnostic purposes. The current review describes the achievements in preparation of multicolor specimens based on QD-conjugates for microscopy and flow cytometry and outlines the requirements for microscope and flow cytometer reengineering for successful analysis of these specimens. However, despite considerable progress, two of the obstacles that preclude wider use of QDs include some of their chemical properties and the large size of QD-conjugates. Difficulties in the application of QDs are similar whether commercial or custom-made conjugates are used.