Effect of Ligand Nature on the Kinetics and the Redistribution of Quantum Dots in Mice

Keywords:
NIR emitting quantum dots, surface coating, bio-distribution

Abstract:
The meeting of nano-materials with biology has produced a new generation of technologies that can profoundly impact biomedical research. The NIR emitting window (650-900 nm) is appealing for in vivo optical imaging because of the low tissue absorption and scattering in this wavelength range. The design of high-quality NIR-emitting quantum dots, with outstanding optical properties in comparison to organic dyes, should therefore lead to novel contrast agents with improved performance (higher fluorescence quantum yields and photo-stability). Quantum dots growth is controlled by the coordination of hydrophobic ligands. Hence, they have to be transferred in water and conveniently coated before their use in vivo. Methods: Several coating strategies are developed in order to: A) prevent quantum dots from flocculating during long-term storage, B) efficiently convert the organic-soluble quantum dots to water-soluble nanoparticles, C) maintain the quantum dot fluorescence quantum yield in biological buffers, and D) maintain the sub-10 nm particle size, necessary for their renal clearance. Results: The speed of first pass extraction of quantum dots towards the reticulo-endothelial system (liver, spleen, bone marrow) depends strongly on the particle size and surface coating (cationic, anionic, neutral, zwitterionic). Conclusion: The surface coating of quantum dots and their hydrodynamic diameter are shown to be the critical parameters in the development of new diagnostic agents.

Nanotech 2008 Conference Program Abstract