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Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de molécules thérapeutiques

Abstract : The aim of this PhD thesis is to develop new nanohybrids based on titanate nanotubes (TiONts) in order to use them as nanocarrier of a therapeutic molecule: a stilbene phenol, 4'-hydroxy-4-(3-aminopropoxy)-trans-stilbene (HAPtS), which is a transresveratrol derivative.TiONts are synthesized by a hydrothermal treatment from a precursor of rutile titanium dioxide. Two methods of hydrothermal synthesis have been studied (the static and dynamic ones): the second approach uses an original hydrothermal device which provides a vigorous mechanical stirring during the hydrothermal process with controllable stirring time par hour. A parametric study was carried out to evaluate the effect of reaction time, temperature and stirring time during the hydrothermal treatment on the morphology of the obtained products. It has been proved that the mechanical stirring has a great accelerating effect on the kinetics of the TiONts formation during the dynamic hydrothermal synthesis. After optimization of the experimental parameters of the dynamic hydrothermal treatment, it was possible to reduce the time of TiONts synthesis to only 2 hours, instead of 48 hours obtained by the static method. Discussions about the crystal structure of TiONts, about their formation mechanism and their transformation into nanoribbons have been also developed based on different characterization techniques (XRD, TEM, TGA, XPS, UV visible, IR and Raman spectroscopies). Their special hollow morphology (10 nm in outer diameter, inner diameter of 4 nm, average length of about 190 nm) and multilayered structure (3 to 5 layers) impart them a high specific surface area (>200 m²/g). Different prefunctionalizations of TiONts by biocompatible organic ligands have been carried out to improve their colloidal stability and to graft reactive functional groups on their surface. The studied ligands are: two catechols (DHCA and L-DOPA), citric acid and two organosilanes (APTES and CPTES). Optimal grafting parameters were determined and the presence of covalent bonds between these ligands and TiONts was highlighted especially by XPS and IR. After prefunctionalization with CPTES, the stilbenic phenol (HAPtS) was successfully grafted onto TiONts-CPTES surface using a condensation reaction between HAPtS and CPTES through nucleophilic substitution. The resulting grafting rate was of about 20 mg/g of TiONts. Finally, one of the originalities of this work was the improvement of TiONts biocompatibility by surface modification with a natural polymer, chitosan (CT). The latter was grafted by two different approaches via covalent bonds (step by step grafting using APTES then glutaraldehyde as two intermediate molecules) or via electrostatic interactions (adsorption). After comparing the two elaborated nanohybrids, obtained by the two grafting approaches, the first cytotoxicity assessment tests were carried out, in vitro (RNA synthesis test and neutral red test) and in vivo (zebrafish test), and the obtained results confirmed the biocompatibility of these nanohybrids towards biological systems. A colloidal stability study of TiONts-CT in various mimicked biological media was also carried out.Keywords: Titanate nanotubes, dynamic hydrothermal synthesis, nanocarriers, nanohybrids, colloidal stability, functionalization, grafting, organic ligands, catechols, organosilanes, stilbenic phenol, chitosan, biocompatibility.
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Fadoua Sallem. Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de molécules thérapeutiques. Chimie théorique et/ou physique. Université Bourgogne Franche-Comté, 2017. Français. ⟨NNT : 2017UBFCK030⟩. ⟨tel-01799041⟩

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