Monique Smaïhi

Cellular localisation of a water-soluble fullerene derivative

Fullerenes are a new class of compounds with potential uses in biology and medicine and many insights were made in the knowledge of their interaction with various biological systems. However, their interaction with organised living systems as well as the site of their potential action remains unclear. In this work, we have demonstrated that a fullerene derivative could cross the external cellular membrane and it localises preferentially to the mitochondria. We propose that our finding supports the potential use of fullerenes as drug delivery agents as their structure mimics that of clathrin known to mediate endocytosis.

Silicalites and Mesoporous Silica Nanoparticles for photodynamic therapy

The synthesis of silicalites and Mesoporous Silica Nanoparticles (MSN), which covalently incorporate original water-soluble photosensitizers for PDT applications is described. PDT was performed on MDA-MB-231 breast cancer cells. All the nanoparticles showed significant cell death after irradiation, which was not correlated with (1)O(2) quantum yield of the nanoparticles. Other parameters are involved and in particular the surface and shape of the nanoparticles which influence the pathway of endocytosis. Functionalization with mannose was necessary to obtain the best results with PDT due to an active endocytosis of mannose-functionalized nanoparticles. The quantity of mannose on the surface should be carefully adjusted as a too high amount of mannose impairs the phototoxicity of the nanoparticles. Fluorescein was also encapsulated in MCM-41 type MSN in order to localize the nanoparticles in the organelles of the cells by confocal microscopy. The MSN were localized in lysosomes after active endocytosis by mannose receptors.

Colloidal functionalized calcined zeolite nanocrystals

Template-free suspensions of functionalized zeolite nanoparticles are obtained by two consecutive grafting procedures. Firstly, organic ligands grafted at template-containing zeolite nanocrystals inhibit irreversible aggregation during the combustion of the structure directing agent. A second grafting provides stable colloidal functionalized zeolite nanocrystals with organic ligands grafted at silicon or aluminium surface zeolite atoms. This procedure is applicable to zeolites with any framework composition and opens up routes for the preparation of various functional materials (controlled release capsules, chemical sensors and adsorbents for example).

Towards thrombosis-targeted zeolite nanoparticles for laser-polarized 129Xe MRI

The synthesis and functionalisation of zeolite nanoparticles designed for laser-polarized 129Xe NMR experiments in solution are described. These nanoparticles were functionalized by using original synthesis pathways through semicarbazide COCHO chemistry in order to ensure anchoring of a peptide for targeting biological receptors and attachment of PEG chains for in vivo experiments. Results demonstrated that accessibility of the dissolved noble gas to the micropores was maintained after functionalization. γ Scintigraphy with 111In linked to the zeolite particles has been investigated in order to follow the behaviour of the zeolite nanoparticles in mice. These preliminary 111In scintigraphy experiments showed the localization of the nanoparticles after injection in mice and their biodistribution, as a first proof-of-concept towards in vivo129Xe MRI.

Hydrolysis and initial polycondensation of phenyltrimethoxysilane and diphenyldimethoxysilane

The sol–gel process opens the possibility of producing vitreous solids containing the main structural groups of oxide glasses and polymers by introducing compounds of the type RnSi(OR′)4–n into the starting mixture. The Si–C bond is normally stable towards hydrolysis and therefore the ligand R acts as a network modifier in the resulting structure. Two organoalkoxysilanes were studied: phenyltrimethoxysilane (PTMOS) and diphenyldimethoxysilane (DPMOS). The compositional regions in PTMOS and DPMOS systems where the solution is homogeneous and the gelation takes place were investigated. The hydrolysis and initial polycondensation of PTMOS and DPMOS were studied by highresolution 29Si nuclear magnetic resonance. Signals due to the following monomers and oligomers have been identified: PhSi(OMe)2(OH); PhSi(OMe)(OH)2; PhSi(OH)3; Ph2Si(OMe)(OH); Ph2Si(OH)2(where Ph=C6H6). Concerning the difunctional alkoxysilane, it was shown that the substitution of the hydroxy group for the methoxy group resulted in an upfield shift of the signal which is opposite to the case for tetrafunctional alkoxides. For the PTMOS, the same substitution induces the conventional downfield shift. 29Si NMR quantitative analysis was performed on both alkoxide solutions during the following of the hydrolysis-condensation reactions and on the final gels. This provided information on the formation of the gels molecular structure.

Silicon and Phosphorus Alkoxide Mixture: Sol-Gel Study by Spectroscopic Technics

Sol-gel synthesis of mixtures of tetraethoxysilane and a phosphorus alkoxide [P(OEt)3 or (OEt)2P-O-P(OEt)2 or PO(OEt)3] have been studied by 1H, 13C29Si and 31P liquid and solid state NMR, infrared and raman spectroscopies. This study shows different behaviors towards hydrolysis for these three different phosphates and phosphites. P(OEt)3 almost instantly reacts with water to form an intermediate species HPO(OEt)2, which slowly evolves first to HPO(OH)(OEt), then to HPO(OH)2 a few days later. For (OEt)2P-O-P(OEt)2, the P-O-P bond is broken when water is added, then the same intermediates are formed faster. PO(OEt)3 is hydrolyzed much slower than the other alkyl phosphates. After ten months, triethoxyphosphate is quantitatively present in the sol with little PO(OH)(OEt)2 species. All these hydrolyzed species are well characterized. Only the system which contains the tetraethoxysilane and the triethoxyphosphite P(OEt)3 forms a few P-O-P and P-O-Si bonds in the gel. Hydrolysis of tetraethoxysilane is much faster than that of phosphorus alkoxides and the conventional Q2, Q3 and Q4 condensed silicon species form the gel three dimensional network.

Template extraction from surface-functionalised zeolite β nanoparticles

Colloidal suspensions of functionalised zeolite nanoparticles have been prepared by a two-step procedure. Organic ligands were grafted to the surface of the zeolite nanoparticles, playing the role of functionalising groups as well as protective groups against framework alteration during subsequent solvent extraction of the structure directing agent (SDA). The effect of each step of the preparation procedure on particle size, morphology, crystallinity and the microporous properties of the material was studied by XRD, DLS, SEM and N2 adsorption measurements. Nanoparticle surface bonding has been investigated by 29Si and 31P MAS NMR. The accessibility and stability of the anchored functional groups on the final materials has been proved by fluorescence spectroscopy. This preparation procedure allows the size, morphology and crystallinity of the initial zeolite nanoparticles to be preserved, while opening the microporosity and modifying their surface reactivity.

Dual templating function of Equisetum arvense in the preparation of zeolite macrostructures

Abstract Biomimetic microporous structures were prepared by in situ laboratory zeolitization of a silica-rich plant, member of the Equisetophyta family. Leaves and stems of the dry plant were subjected to hydrothermal treatment into a clear ZSM-5 precursor solution. Highly reactive biomorphic silica deposited at the epidermal surface of the plant successfully promoted zeolite growth and provided composites containing up to 70 wt. % ZSM-5. The zeolite/plant composites were transformed into all-zeolite materials by high temperature calcination. Both the as-synthesized zeolite/plant composites and all-zeolite replicas were studied by XRD, TG/DTA analysis, SEM, TEM, N 2 adsorption measurements. The analysis of the synthesized composites and their replicas showed that tiny zeolite nanoparticles crystallizing at the tissues of the biotemplate generated mesopores. Thus, the utilization of a biological template allowed to synthesize a micro-/mesoporous material with specific macromorphological features.

Room temperature synthesis: an efficient way for studying the zeolite formation

The synthesis and the detail investigation of the formation of LTA-and FAU-type zeolites at room temperature (RT) are reported. The complete transformation of the amorphous precursors into zeolite A and X took place for 3 and 21 days, respectively. The events taking place at the nanometer scale were studied by high resolutions transmision electron microscopy (HRTEM). The study was completed by small angle X-ray scattering (SAXS) and X-ray diffraction (XRD). The sluggish crystal growth kinetics at ambient conditions permitted to track down the entire sequence of crystallization events from the formation of the initial gel to the complete transformation into a zeolite-type material. Liquid inclusions denoted as “negative crystals” were found within the volume of the gel partile for both systems. Further, the crystal growth was followed by HRTEM, which revealed that the crystallization in the two systems is governed by different crystallization mechanism.

Fluorescent colloidal microporous nano-zeolites

Fluorescent colloidal zeolite nanoparticles have been prepared by adsorption of organic chromophores in the porous network of template-free zeolite beta nanoparticles. The colloidal properties of the particles are maintained after confinement of the dyes in the microporous cavities so that conventional optical transmission spectroscopic methods can be used to study the entrapped chromophores species within the zeolite. The dye entrapment is stable towards acidic treatments and extensive reflux processing. The dye loading (given by elemental analysis) can be controlled by the preparation procedure and the effectiveness of the confinement is attested by fluorescence spectroscopy studies.