Single-molecule imaging with quantum dots

Quantum dots (QDs) are a class of fluorescent nanocrystal with unique optical and electronic properties (Smith et al. 2008; Smith and Nie 2009a). Originally investigated as components for light-emitting devices, solar cells, and catalysts in the early 1980s, these particles were introduced in 1998 as optical tags for bioimaging and biological detection (Chan and Nie 1998; Bruchez et al. 1998). Over the ensuing 15 years, their most significant contribution to biomedicine has been in the field of single-molecule fluorescence microscopy, for which they have filled a major need for bright fluorescent probes with long-term photostability. These particles are now widely used for imaging the dynamics of individual molecules and the interactions between molecules in complex biological environments.