Hydrodynamic sizes of functional hydrophilic QDs

Thomas Pons; Igor L. Medintz; Hedi Mattoussi

doi:10.1117/12.641767

27 March 2006 Hydrodynamic sizes of functional hydrophilic QDs

Thomas Pons, Igor L. Medintz, Hedi Mattoussi

Proceedings Volume 6096, Colloidal Quantum Dots for Biomedical Applications; 60961H (2006) https://doi.org/10.1117/12.641767
Event: SPIE BiOS, 2006, San Jose, California, United States

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.

Citation Download Citation

Thomas Pons, Igor L. Medintz, and Hedi Mattoussi "Hydrodynamic sizes of functional hydrophilic QDs", Proc. SPIE 6096, Colloidal Quantum Dots for Biomedical Applications, 60961H (27 March 2006); https://doi.org/10.1117/12.641767

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