Advances in recent nanoscience technologies have generated a new compilation of biocompatible, fluorescent nanoparticles derived from semiconductor quantum dots (QDs). QDs are extremely small in size and possess very large surface areas, which gives them unique physical properties and applications distinct from those of bulk systems. When exposed to biological fluid, these QDs may become coated with proteins and other biomolecules given their dynamic nature. These protein-QD systems may affect or enhance the changes in protein structure and stability, leading to the destruction of biological function. It is believed that these QDs can act as nucleation centers and subsequently promote protein fibril formation. Protein fibrillation is closely associated with many fatal human diseases, including neurodegenerative diseases and a variety of systemic amyloidoses. This topic of protein-QD interaction brings about many key issues and concerns, especially with respect to the potential risks to human health and the environment. Herein, the behavioral effects of dihydrolipoic acid (DHLA)-capped CdSe/ZnS (core/shell) QDs in hen egg-white lysozyme (HEWL) and human serum albumin (HSA) protein systems were systematically analyzed. This study gives rise to a better understanding of the potentially useful application of these protein-QD systems in nanobiotechnology and nanomedicine as a bioimaging tool and/or as a reference for controlled biological self-assembly processes.

Ce travail décrit une nouvelle route synthétique qui a pour objectif l'obtention de diblocs amphiphiles constitués uniquement d'oligosaccharides issus de xyloglucanes des graines de Tamarin. Les xylogluco-oligosaccharides (XGOs, DP7, 8, 9) de tailles parfaitement définies ont été obtenus par une digestion enzymatique contrôlée (cellulase) de xyloglucanes. Dans la perspective de lier les deux blocs par cycloaddition 1,3-dipolaire de Huisgen catalysée par le Cuivre I, dite aussi chimie « click », les XGOs ont subit une réaction d'amination réductrice assistée par micro-ondes. L'action de la propargylamine a permis d'intégrer en position réductrice du XGO la fonction alcyne et une peracétylation des focntions hydroxyles du sucre ont rendu ce bloc hydrophobe. D'un autre côté, l'azidoethylamine a permis d'insérer la fonction azoture et constitue le bloc hydrophile. Cette stratégie de synthèse a également été transposée à un oligosaccharide monodisperse (XGO, DP7) provenant de la dégalactosylation enzymatique du xyloglucane par l'action supplémentaire de la galactosidase d'Aspergillus Niger. Finalement, les diblocs amphiphilies ont été synthétisé aussi bien à partir des XGOs de DP7, 8, 9 (XGO-b-XGO,Ac), que du XGO DP7 (DP7-b-DP7,Ac). Leurs propriétés d'auto-assemblages dans l'eau ont été réalisées ainsi que leur caractérisation physico-chimique. Suite à des mesures de concentration micellaire critique (CMC) obtenus par spectroscopie de fluorescence du pyrène, nous avons observé que l'élimination des unités de galactose provoque une augmentation de la CMC. La détermination du diamètre des micelles en solution aqueuse a été réalisée grâce à la technique de diffusion de la lumière (DLS) et a été confirmée par microscopie électronique à transmission (MET). Des micelles sphériques d'une taille moyenne de 25 nm (XGO-b-XGO,Ac) et de 6 nm (DP7-b-DP7,Ac) ont été observées au MET. La digestion enzymatique partielle des micelles formés à partir du dibloc XGO-b-XGO,Ac dans l'eau, conduisant à la formation des micelles DP7-b-XGO,Ac a conduit à un système moins polydisperse et à une diminution de la taille moyenne du diamètre micellaire de l'ordre de 50% (déterminée par DLS). Des nanoparticules de gliadine et de zéine ont été préparées par désolvatation en utilisant le dibloc XGO-b-XGO,Ac comme surfactant en comparaison au surfactant commercial non-ionique, le Pluronic F68. Les résultats suggèrent la capacité du dibloc à stabiliser la protéine de zéine sous forme de nanoparticules sphériques et de façon relativement monodisperses. Les particules formées et stabilisées grâce à l'association de protéines d'origine végétale et d'un surfactant « biopolymérique » synthétisé uniquement par des oligosaccharides, apparaissent comme des systèmes idéaux, associant biocompatibilité, biodégradabilité et des origines naturelles et renouvelables. Ces systèmes peuvent tout à fait être valorisés pour la libération contrôlée de substances actives. / This work describes a new synthetic route to obtain fully oligosaccharides-based amphiphilic diblock copolymers, made from tamarind seeds xyloglucan. A mixture of well size-defined xyloglucooligosaccharides (XGO of 7, 8 and 9 carbohydrate units) were obtained from the cellulose-mediated enzymatic digestion of xyloglucanes. To perform the Huisgen click reaction the oligosaccharides were reducing end functionalized by azide and propargyl functions via microwave-catalyzed reductive amination. The hydrophobic block was obtained after peracetylation of alkyne-containing XGO. The amphiphilic co-oligomers were synthesized either from the mixture of xyloglucan oligosaccharides to give XGO-b-XGO,Ac, either from the monodisperse XGO of 7 carbohydrate units (DP7), obtained by a degalactosylation process involving another specific enzymatic hydrolysis (beta-galactosidase from Aspergillus Niger), to give DP7-b-DP7,Ac. The XGO-based diblocks were characterized according to the state-of-the-art in structural characterization (NMR, MS, FT-IR) and Soft Matter physico-chemistry (SLS, DLS, CMC, TEM) techniques. The removal of galactose units (DP7-b-DP7,Ac) conferred an increase in the critical micellar concentration value compared to XGO-b-XGO,Ac, which were determined by fluorescence spectroscopy. The size diameter of the micelles were carried out by dynamic light scattering (DLS) and confirmed by transmission electron microscopy (TEM). Spherical micelles with an average size of 25 nm for XGO-b-XGO,Ac and 6 nm DP7-b-DP7,Ac nanoparticles were observed by TEM. The partial enzymatic digestion of the shell constituting XGO-b-XGO,Ac micelles in water led to formation of DP7-b-XGO,Ac micelles with a lowest polydispersity and a decrease in the average size diameter by 50 %, as determined by DLS. XGO-b-XGO,Ac was tested as a nonionic block copolymer surfactant to stabilize zein and gliadin nanoparticles, which come from gluten of wheat and maize and were prepared by the method of desolvation. Its stabilizing properties were compared to Pluronic F68 surfactant belonging to poloxamers' family. The results suggest the suitability of the XGO-based diblock to stabilize zein aggregates, resulting in stable, monodisperse and spherical nanoparticles. Finally, this work proposed a system consisting in potential nanocarriers prepared from vegetable proteins stabilized by biosourced oligosaccharide surfactants.

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Due to their therapeutic applications such as radical scavenging, MRI contrast imaging, Photoluminescence imaging, drug delivery, etc., nanoparticles (NPs) have a significant importance in bio-nanotechnology. The reason that prevents the utilizing NPs for drug delivery in medical field is mostly due to their biocompatibility issues (incompatibility can lead to toxicity and cell death). Changes in the surface conditions of NPs often lead to NP cytotoxicity. Investigating the role of NP surface properties (surface charges and surface chemistry) on their interactions with biomolecules (Cells, protein and DNA) could enhance the current understanding of NP cytotoxicity. Hence, it is highly beneficial to the nanotechnology community to bring more attention towards the enhancement of surface properties of NPs to make them more biocompatible and less toxic to biological systems. Surface functionalization of NPs using specific ligand biomolecules have shown to enhance the protein adsorption and cellular uptake through more favorable interaction pathways. Cerium oxide NPs (CNPs also known as nanoceria) are potential antioxidants in cell culture models and understanding the nature of interaction between cerium oxide NPs and biological proteins and cells are important due to their therapeutic application (especially in site specific drug delivery systems). The surface charges and surface chemistry of CNPs play a major role in protein adsorption and cellular uptake. Hence, by tuning the surface charges and by selecting proper functional molecules on the surface, CNPs exhibiting strong adhesion to biological materials can be prepared. By probing the nanoscale interaction forces acting between CNPs and protein molecules using Atomic Force Microscopy (AFM) based force-distance (F-D) spectroscopy, the mechanism of CNP-protein adsorption and CNP cellular uptake can be understood more quantitatively. The work presented in this dissertation is based on the application of AFM in studying the interaction forces as well as the mechanical properties of nanobiomaterials. The research protocol employed in the earlier part of the dissertation is specifically aimed to understand the operation of F-D spectroscopy technique. The elastic properties of thin films of silicon dioxide NPs were investigated using F-D spectroscopy in the high force regime of few 100 nN to 1 µN. Here, sol-gel derived porous nanosilica thin films of varying surface morphology, particle size and porosity were prepared through acid and base catalyzed process. AFM nanoindentation experiments were conducted on these films using the F-D spectroscopy mode and the nanoscale elastic properties of these films were evaluated. The major contribution of this dissertation is a study exploring the interaction forces acting between CNPs and transferrin proteins in picoNewton scale regime using the force-distance spectroscopy technique. This study projects the importance of obtaining appropriate surface charges and surface chemistry so that the NP can exhibit enhanced protein adsorption and NP cellular uptake.