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Understanding the Light-Induced Cytotoxicity of Quantum Dots: A Cellular, Photophysical, and Mechanistic Approach

Franoise Winnik
University of Montreal, Montreal, Quebec, Canada

Quantum dots (QDs), nanometer-sized light emitting semiconductor (i.e., CdSe) particles, are emerging as a new class of fluorescent probes for in vivo and cellular imaging. Due to their size, they have unique optical properties such as size-tunable emission from green to red, resistance to photo bleaching, and high emission quantum yield. Two decades ago, QDs were confined to physicists' laboratories. In 2005, QDs are commercially available worldwide in numerous forms. They are used in bioimaging, either per-se or conjugated to biopolymers, DNA, and proteins, thus enabling target-specific imaging. They can act as energy donor in FRET experiments and, as demonstrated recently, they can also be used as photosensitizers. The latter property is particularly exciting because it could lead to novel forms of in vivo photodynamic therapy.

Not surprisingly, the potential toxic effects of semiconductor QDs have become a topic of considerable importance and discussion. Indeed in vivo toxicity is likely to be a key factor in determining whether QD imaging probes would be approved by regulatory agencies for clinical human use. Recent publications by us and by others indicate that QDs can be highly toxic to cells under irradiation, although under given conditions QDs are much more benign. The project focuses on the light-induced potential toxicity of QDs, using a three-pronged mechanistic approach: solution photophysics, cell imaging, and quantitative analysis of released harmful ions (Cd2+).

The outcome of the study will be a better understanding of a key aspect of QD cytotoxicity, an appraisal of various means to alleviate their deleterious effects, and the delineation of predictive guidelines for QDs cytotoxicity.

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