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Semiconductor nanocrystals : new fluorescent probes for advanced biological imaging
par - 27 février 2007
Ce travail est réalisé en collaboration avec Christophe Tribet (ESPCI), Valérie Marchi-Artzner (SESO Rennes).
Introduction
In our laboratory we are interested in understanding single molecule dynamics in live cells. For this purpose semiconductor nanocrystals (NCs) represent a suitable visualization tool, since, being more photostable than conventional dyes (like organic fluorophores or fluorescent proteins) they allow imaging over a long period of times. In addition, NCs also have a high sensitivity and resolution, which are critical factors for accurate single molecule tracking. However, since semiconductor nanocrystal application in biological context is still limited by their hydrophobic outer shell we are also interested in understanding their surface chemistry properties. In particular we are focused on the development of new solubilization and conjugate techniques to provide water solubility and binding specificity for these nanoparticles.
Semiconductor nanocrystal solubilisation
Many different strategies exist to make NCs water soluble and thus biocompatible. In our lab we follow two different solubilization procedures : 1) adsorption of bifunctional ligands and 2) monolayer coating with short amphipathic polymer. In principle, in the first case the surfactant molecules, which cover the NC surface, are replaced with bifunctional molecules, that are hydrophobic on one end and hydrophilic on the other. In the other case the hydrophobic side of the amphipatic polymer interact and mask the surfactant molecules. Finally, in both cases the resulting nanoparticles have an hydrophilic group facing the solution and ensuring the following bioconjugation step.
Adsorption of bifunctional ligands
In this procedure as bifunctional compounds we use different kinds of peptides. In collaboration with Valéèrie Marchi-Artzner (SESO, Rennes), we are analyzing the peptide coated nanocrystal surface by dynamic light scattering and fluorescence microscopy. In order to test the peptide coating specificty of nanocrystals we study their interaction with lipid vesicles, as a simple model of biological membranes.
Monolayer coating with short amphipathic polymer
The monolayer coating with short amphipathic polymer, synthesized by Christophe Tribet, at the ESPCI, allows us to have water soluble semiconductor nanocrystals whose size and chemical features are characterized by various techniques such as : QELS, capillary electrophoresis and transmission electron microscopy.
Semiconductor nanocrystal bioconjugation
This step is essential to allow the linkage of the water soluble nanocrystal to the biological molecules of interest. Depending on the molecule target, different procedures of conjugation can be followed. Until now we have being working on coupling of NCs to : IgGs, streptavidin and protein A.
Mots-clés
Optique et Biologie
