Etude du greffage par thiols de couches mixtes de Polyéthylènes Glycols (PEG-Méthoxy et PEG-Alcyne) sur Nanoparticules d'Or (GNPs)

In the recent years, the scientific community has witnessed a growing interest in nanotechnology. Nanomaterials, defined as having at least one dimension between 1nm and 100 nm, have particularly interesting properties that allow the development of new applications. In nanomedicine, Gold Nanoparticles are very appreciated due to their optical and photo-thermal properties, consequence of the Localized Surface Plasmon Resonance Phenomenon. Nowadays, they find in diagnostic and therapeutic applications. By the functionalizing of the gold nanoparticles, it is possible to provide new properties to these particles : stability, biocompatibility and targeting abilities. To do this, we can use Polyethylene Glycols (PEGs) as passivating ligands using thiol groups, which have a strong affinity for the gold surface. Our project will focus on the conditions to graft mixtures of thiolated molécules in controlled ratios on the surface of the GNPs. First, we have studied two différents types of thiolated PEGs : one presenting an alkyne group and one presenting a methoxy group. The first PEG will be used to post-functionalise the GNPs with organic ligands while the second one is a passivating ligand. We have performed different experiments with différents ratios of the two PEGs. NMR and UV-Visible Spectroscopies have been used to quantified densities. Then, we investigated the grafting of the PEG-alkyne simultaneously with mercaptopropionic acid or mecaptoundecanoic acid. Results obtained with the PEG-alkyne seems to indicate an interaction of the alkyne functional group with the surface and we hoped that the presence of negative charges on the surface of the GNPs would prevent that interaction. Finally, we have optimized the conditions of the post-functionalization of the alkyne functional group using click-chemistry with copper sulfate by grafting -N3 containing fluorescent dye that allows the quantification by absorption spectroscopy of the amount of grafted molécules. Our results confirm a former study of the EMNS laboratory that has highlighted that the grafting of the mixtures of thiolated molécules on GNPs is not controllable, and that the proportions used in the functionalization solution are not at the surface of the GNPs.