Synthèse de nanotubes de carbone remplis et de nanoparticules encapsulées dans des coques de carbone pour applications biomédicales

Ce travail a été effectué dans le cadre du projet européen Carbio FP6 RTN (www.carbio.eu), visant à exploiter le potentiel des DWNT (Double Walled Carbon Nanotubes) multifonctionnels et de nanoparticules métalliques encapsulées pour une application biomédicale, en particulier pour agir en tant que nano-dispositifs magnétiques chauffants pour le traitement du cancer par hyperthermie ou comme nano-véhicules de transport de médicaments. Pour atteindre ces objectifs, les DWNT ont d'abord été synthétisé par CCVD en présence d'un mélange H2-CH4 et de catalyseurs (Mg, Co, Mo). Afin de combler le vide de la cavité des DWNT avec des matériaux magnétiques, les extrémités des tubes doivent être ouverts. L'ouverture des DWNT a été réalisée dans différentes conditions : par voie humide tels que l'oxydation avec HNO3, HNO3/H2SO4, KMnO4 ou K2Cr2O7 ou par voie sèche impliquant l'oxydation à l'air ou le chauffage par micro-ondes. En raison des inconvénients de certaines techniques d'ouverture (échantillon de revêtement des nanotubes par des débris d'oxydation), nous avons développé des méthodes de purification supplémentaires telles que le lavage par la soude, l'oxydation à l'air ou le chauffage par micro-ondes. Le remplissage des DWNT été réalisée en utilisant une seule étape (remplissage lors de l'ouverture des tubes) ou en deux étapes (après l'ouverture) dans des solutions saturées de nitrate ou de chlorure de fer (III), dans des conditions différentes afin d'évaluer l'influence du temps d'agitation, de la concentration et de la température. Des expériences de contrôle de remplissage avec des composés d'uranium ont été réalisées. Une deuxième stratégie que nous avons développée dans ce travail a été la synthèse directe CCVD de nanoparticules de Fe, Co, Co / Fe et Ni encapsulées dans du carbone. Les nanoparticules encapsulées ont été synthétisées avec des mélanges gazeux de H2/CH4 ou N2/CH4, en utilisant différents catalyseurs à base de MgO (solutions solides Mg0.95Co0.05O, Mg0.95Fe0.05O, Mg0.95Co0.025/Fe0.025O et Mg0.95Ni0.05O). Les échantillons obtenus correspondent par exemple à des nanoparticules sphériques et / ou oblongue de Co encapsulé avec une distribution de taille : 6-10 nm (60%) et 11-20 nm (40%). Des nanoparticules encapsulées oblongues ou sphériques ont également été observées avec du Fe et du Co / Fe, avec un diamètre dans la gamme 1-10 nm (80%) et 11-30 nm (20%). Le matériau le plus prometteur pour l'application en hyperthermie a été obtenu avec des nanoparticules de Co qui ont montré la saturation de magnétisation la plus élevée à température ambiante (Ms) et le plus haut taux d'absorption spécifique (SAR).This work was performed in the framework of the European FP6 RTN CARBIO (www.carbio.eu) project, aiming at exploiting the potential of multi- functional DWNT and Carbon encapsulated metal nanoparticles for biomedical application, in particular to act as magnetic nano-heaters(cancer treatment by hyperthermia) or drug - carrier systems. To achieve these goals, DWNT have first been synthesised by catalytic chemical vapour deposition (CCVD) of a H2-CH4 mixture over (Mg, Co, Mo)O catalysts. In order to fill the empty cavity of DWNT with magnetic materials, the tips of the tubes have to be opened. The opening of DWNT was performed in different conditions using wet chemistry routes such as oxidation with HNO3, HNO3/H2SO4, KMnO4 or K2Cr2O7 or dry routes involving air oxidation or microwave heating. Due to drawbacks of some of the opening techniques (sample coating with amorphous oxidation debris), we have developed extra purification methods such as NaOH washing, oxidation in air or microwave heating. The filling of DWNT was performed using one-step (during the opening) or two-step (after the opening) methods in over-saturated iron (III) nitrate or iron (III) chloride solutions, in different conditions in order to assess the influence of stirring time, concentration and temperature. Control experiments of filling with uranium compounds were performed. A second strategy that we have developed in this work was the direct CCVD synthesis of carbon-encapsulated Fe, Co, Co/Fe and Ni nanoparticles. The encapsulated nanoparticles have been synthesized with gaseous mixtures of H2/CH4 or N2/CH4, using different MgO-based catalysts (Mg0.95Co0.05O, Mg0.95Fe0.05O, Mg0.95Co0.025/Fe0.025O and Mg0.95Ni0.05O solid solutions). The obtained samples correspond for example to spherical and/or oblong carbon-encapsulated Co nanoparticles with size distribution 6-10 nm (60%) and 11-20 nm (40%). Oblong or spherical carbon-encapsulated nanoparticles were also observed with Fe and Co/Fe, with diameter within the range 1-10 nm (80%) and 11-30 nm (20%). The most promising material for hyperthermia application was found to be the carbon-encapsulated Co nanoparticles which showed the highest saturation magnetisation at room temperature (Ms) and the highest Specific Absorption Rate (SAR)

AFM imaging of functionalized double-walled carbon nanotubes

We present a comparative study of several non-covalent approaches to disperse, debundle and noncovalently functionalize double-walled carbon nanotubes (DWNTs). We investigated the ability of bovine serum albumin (BSA), phospholipids grafted onto amine-terminated polyethylene glycol (PLPEG2000-NH2), as well as a combination thereof, to coat purified DWNTs. Topographical imaging with the atomic force microscope (AFM) was used to assess the coating of individual DWNTs and the degree of debundling and dispersion. Topographical images showed that functionalized DWNTs are better separated and less aggregated than pristine DWNTs and that the different coating methods differ in their abilities to successfully debundle and disperse DWNTs. Height profiles indicated an increase in the diameter of DWNTs depending on the functionalization method and revealed adsorption of single molecules onto the nanotubes. Biofunctionalization of the DWNT surface was achieved by coating DWNTs with biotinylated BSA, providing for biospecific binding of streptavidin in a simple incubation step. Finally, biotin-BSA-functionalized DWNTs were immobilized on an avidin layer via the specific avidin–biotin interaction

Synthesis of superparamagnetic iron(III) oxide nanowires in double-walled carbon nanotubes

The synthesis and characterization of superparamagnetic iron(III) oxide nanowires confined within double-walled carbon nanotubes by capillary filling with a melted precursor (iron iodide) followed by thermal treatment is reported for the first time

Double-walled carbon nanotubes: Quantitative purification assessment, balance between purification and degradation and solution filling as an evidence of opening

We compared the effect of different oxidizing agents on purification, functionalization and opening of double-walled carbon nanotubes. The oxidative treatments were realized in nitric acid solutions at different concentrations (3 M or 15 M), in a mixture of two oxoacids (conc. HNO3/conc. H2SO4) or in sulphuric acid solutions of KMnO4 or K2Cr2O7. Most of these treatments were very efficient for purification (removal of residual catalytic metal nanoparticles and/or of disorganized carbon) but also caused secondary reactions such as shortening of the nanotubes, creation of functionalized amorphous carbon deposits and covalent functionalization of the outer wall. Secondary treatments were undertaken in order to remove functionalized carbon deposit by washing with sodium hydroxide solutions or by heat treatment in air. A partial filling in solution was obtained with uranyl nitrate, in order to evidence the opening of carbon nanotubes. Effects of purification and filling treatments were characterized both qualitatively by TEM and HRTEM, AFM and Raman spectroscopy, and quantitatively by elemental chemical analysis and chemical titrations

Optimising DNA binding to carbon nanotubes by non-covalent methods

The use of carbon nanotubes as a gene delivery system has been extensively studied in recent years owing to its potential advantages over viral vectors. To achieve this goal, carbon nanotubes have to be functionalized to become compatible with aqueous media and to bind the genetic material. To establish the best conditions for plasmid DNA binding, we compare the dispersion properties of single-, double- and multi-walled carbon nanotubes (SWCNTs, DWCNTs and MWCNTs, respectively) functionalized with a variety of surfactants by non-covalent attachment. The DNA binding properties of the functionalized carbon nanotubes were studied and compared by electrophoresis. Furthermore, a bilayer functionalization method for DNA binding on SWCNTs was developed that utilized RNA-wrapping to solubilize the nanotubes and cationic polymers as a bridge between nanotubes and DNA

Synthèse de nanotubes de carbone remplis et de nanoparticules encapsulées dans des coques de carbone pour applications biomédicales

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

A single-molecule approach to explore binding, uptake and transport of cancer cell targeting nanotubes

International audienceIn the past decade carbon nanotubes (CNTs) have been widely studied as a potential drug-delivery system, especially with functionality for cellular targeting. Yet, little is known about the actual process of docking to cell receptors and transport dynamics after internalization. Here we performed single-particle studies of folic acid (FA) mediated CNT binding to human carcinoma cells and their transport inside the cytosol. In particular, we employed molecular recognition force spectroscopy, an atomic force microscopy based method, to visualize and quantify docking of FA functionalized CNTs to FA binding receptors in terms of binding probability and binding force. We then traced individual fluorescently labeled, FA functionalized CNTs after specific uptake, and created a dynamic 'roadmap' that clearly showed trajectories of directed diffusion and areas of nanotube confinement in the cytosol. Our results demonstrate the potential of a single-molecule approach for investigation of drug-delivery vehicles and their targeting capacity