Authors: S.J. Clarke, C.A. Hollmann and J.L. Nadeau
Affilation: McGill University, Canada
Pages: 451 - 454
Keywords: electron transfer, subcellular localization, cytotoxicity, fluorescent labeling
The interactions of semiconductor quantum dots (QDs) with living cells remain poorly understood. It is known that certain sizes (colors) of QDs penetrate more readily into subcellular compartments, such as the nucleus, or into bacteria. QDs also show oxidative toxicity to cells and cellular organelles such as mitochondria; certain conjugates may increase this toxicity. A quantitative understanding of the relationship between QD photophysics and biological systems is hence critical if these particles are to be used in in vitro diagnostics or in vivo systems. Understanding toxicity is also important for rational development of regulations concerning environmental release of manufactured nanomaterials.In this work, we find that CdSe/ZnS quantum dot (QD) conjugates to specific electron donors, particularly dopamine, have particular spectral properties that allow visual distinction of various stages of their processing in cells, both mammalian cells and bacteria. Little toxicity is seen when the particles are retained within lysosomes, although removal of the cap by lysosomal proteases can be observed. However, brief exposure to light (or glutathione depletion) are sufficient to release particles into other parts of the cell. Severe damage is seen when QDs associate with mitochondria, associated with oxidation of the QDs and blebbing and rupture of the mitochondrial membranes.