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Proceedings Paper

Hydrodynamic sizes of functional hydrophilic QDs
Author(s): Thomas Pons; Igor L. Medintz; Hedi Mattoussi
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Paper Abstract

Semiconductor nanocrystal quantum dots (QDs) have a great potential for use in biological assays and imaging, due to their unique optical properties. These inorganic nanocrystals are coated with ligands (bifunctional ligands, amphiphilic polymers, phospholipids) that provide them with both hydrophilicity and functionalization. The nanoparticle hydrodynamic radius and electric charge are particularly important parameters as they influence properties such as their diffusion inside live cells or tissues. Techniques such as transmission electron microscopy probe only the nanocrystal core size and don't take into account the size of the ligand coating. We use dynamic light scattering (DLS) to characterize the hydrodynamic diameter (DH) and polydispersity of CdSe/ZnS core-shell QDs capped with various types of hydrophilic surface coatings (dihydrolipoic acid (DHLA), poly(ethylene glycols)-terminated dihydrolipoic acid (DHLA-PEG), amphiphilic polymers, and the native trioctylphosphine/trioctylphosphine oxide (TOP/TOPO) used for solubilization in organic solvents), and of QDs/proteins conjugates. We observe a consistent increase in the hydrodynamic radius with the increasing size of the inorganic core and with the lateral extension of the hydrophilic coating materials. We complement our studies with a derivation of the zeta potential and effective charge of nanoparticles capped with purely charged ligands (DHLA) or encapsulated in a charged polymer using agarose gel electrophoresis. These properties are extremely relevant for designing assay and sensing schemes based on fluorescence resonance energy transfer (FRET) as well as diffusion in live cells, for instance.

Paper Details

Date Published: 27 March 2006
PDF: 10 pages
Proc. SPIE 6096, Colloidal Quantum Dots for Biomedical Applications, 60961H (27 March 2006); doi: 10.1117/12.641767
Show Author Affiliations
Thomas Pons, Naval Research Lab. (United States)
Johns Hopkins Univ. (United States)
Igor L. Medintz, Naval Research Lab. (United States)
Hedi Mattoussi, Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 6096:
Colloidal Quantum Dots for Biomedical Applications
Marek Osinski; Kenji Yamamoto; Thomas M. Jovin M.D., Editor(s)

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