Quantum dots in biology and medicine

Semiconductor quantum dots (QDs) are nanometer-sized crystals with unique photochemical and photophysical properties that are not available from either isolated molecules or bulk solids. In comparison with organic dyes and fluorescent proteins, these quantum-confined nanoparticles are brighter, more stable against photobleaching, and can be excited for multicolor emission with a single light source. Recent advances have shown that nanometer-sized semiconductor particles can be covalently linked with biorecognition molecules such as peptides, antibodies, nucleic acids, or small-molecule ligands for use as biological labels. High-quality QDs are also well suited for optical encoding and multiplexing applications due to their broad excitation profiles and narrow/symmetric emission spectra. In this article, we discuss recent developments in QD synthesis and bioconjugation, their applications in molecular and cellular imaging, as well as promising directions for future research.