Gaelle Derrien

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.

Two-Photon-Triggered Drug Delivery in Cancer Cells Using Nanoimpellers†

A therapy of cancer cells: Two-photon-triggered camptothecin delivery with nanoimpellers was studied in MCF-7 breast cancer cells. A fluorophore with a high two-photon absorption cross-section was first incorporated in the nanoimpellers. Fluorescence resonance energy transfer (FRET) from the fluorophore to the azobenzene moiety was demonstrated.

Interactions of phenol with cationic micelles of hexadecyltrimethylammonium bromide studied by titration calorimetry, conductimetry, and 1H NMR in the range of low additive and surfactant concentrations

Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and (1)H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for PhOH/HTAB/H(2)O systems based on the specific conductivity measurements and calorimetric determination of the cumulative enthalpy of dilution as functions of the surfactant concentration at a fixed additive content. The combined analysis of the results obtained in H(2)O solutions pointed to the preferential location of PhOH in the outer micelle parts by an enthalpy-driven mechanism. Additional PhOH molecules were located increasingly deeper within the micelle core. The (1)H NMR study of PhOH solubilization by 1.5 mmol kg(-1) HTAB solutions in D(2)O indicated that the two categories of the solubilization site became saturated with the solubilizate already at the lowest additive content. Dissimilar amounts of the solubilized material in H(2)O and D(2)O solutions were ascribed to the difference in the initial micelle structures formed in the two solvents, as inferred from calorimetry and (1)H NMR studies of the HTAB micellization in D(2)O and H(2)O.

Aqueous behaviour of cationic surfactants containing a cleavable group.

The aggregation behaviour of two novel cationic RAFT agents (transfer surfactants); N,N-dimethyl-N-(4-(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)-carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB) in diluted solutions have been investigated by surface tension, conductimetry and microcalorimetry measurements. The thermodynamic parameters i.e. the critical micelle concentration (cmc), the degree of micelle ionization (alpha), the head group surface area (a 0), Delta H mic, Delta G mic and T Delta S mic are reported at 303 K. The thermodynamic parameters have been compared to those of the conventional surfactant cetyltrimethylammonium bromide (CTAB) in order to specify structural relationships. The obtained results have been discussed considering the hydrophobic behaviour of the S-C=S- linkage and the specific interactions that arise from the introduction of the benzene ring into the hydrophobic part.

One Step Synthesis of Gold-Loaded Radial Mesoporous Silica Nanospheres and Supported Lipid Bilayer Functionalization: Towards Bio-Multifunctional Sensors

A simple synthetic route is developed to achieve gold functionalized radial mesoporous silica nanoparticles (Au-MsNP) synthesized by a one step procedure fully compatible with basic conditions required for the preparation of monodispersed nanospheres. In a second step, Au-MsNP particles have been coated with phospholipid bilayers in order to design an advanced biofunctional platform with the gold metallic nanoparticles previously grown into the pore channels and responsible for a plasmonic activity relevant for biosensing. The size of Au-MsNP is checked by dynamic light scattering while zeta potential measurements reflect their surface charge. The particle morphology is characterized by transmission and scanning electron microscopy and the Si/Au ratios are obtained from energy dispersive X-ray analysis. The textural properties of Au-MsNP, specific surface area and pore size, are determined from N(2) adsorption. The supported bilayers are achieved from vesicles of different phospholipids incubated with Au-MsNP particles. The coating efficiency is investigated by zeta potential and cryo- transmission electron microscopy. The plasmonic activities of bare Au-MsNP particles and coated lipid bilayer Au-MsNP platform are evidenced for two model systems: direct adsorption of bovine serum albumin and molecular recognition events between avidin molecules and biotin receptors integrated in the supported lipid bilayer.

Aluminium-derivatized silica monodisperse nanospheres by a one-step synthesis-functionalization method and application as acid catalysts in liquid phase

Aluminium-derivatized submicron-in-size silica spheres (Al-MSS), with controllable morphology, particle size, mesoporosity, and incorporation of an active phase at the internal surface, have been prepared by a one-step synthesis-functionalization method in view of potential applications in the liquid phase. Four Al-MSS samples were prepared with a molar Si/Al ratio in the initial gel of 44, 22, 11, and 7, and their properties were compared with those of a purely siliceous sample (MSS). Nitrogen adsorption, XRD, SEM and TEM studies revealed homodispersed particles with average diameters ranging between 350 and 520 nm and possessing radial porosity. BET specific surface areas were included between 900 and 1300 m2 g−1 and the average pore diameter varied from 3 to 3.4 nm. Surface reactivity and Al accessibility at the material surface were determined with measurements of two-cycle ammonia adsorption and EDX-based calculations. The best compromise between textural parameters, surface properties, and stoichiometric Al incorporation was achieved with Al-MSS-22. This sample was further characterized by 129Xe-NMR, 27Al-MAS-NMR, XPS, NH3-TPD and IR methods to confirm the high accessibility of its internal porous structure and the presence of weak Bronsted and strong Lewis acid sites on its surface. The catalytic behavior of Al-MSS-22 in the liquid phase was tested in esterification reactions of ethanoic acid with alcohols or polyols such as butanol, isoamyl alcohol, ethylene glycol, and glycerol. In the case of alcohols, the remarkable performance of this aluminosilicate was supported by conversion rates close to 100%, allowing the amount of the catalytic material to be significantly decreased compared with other systems already tested in the literature.

Pentabarium tetraantimonide, β-Ba5Sb4 : a more symmetrical arrangement for the Ba5Sb4 compound

Ba 5 Sb 4 crystallizes in the orthorhombic space group Cmca and is isostructural with Eu 5 As 4 reported in the Ccmb alternate setting. β-Ba 5 Sb 4 is a new arrangement which is more symmetrical than α-Ba 5 Sb 4 [Brechtel, Cordier & Schafer (1981). Z. Naturforsch. Teil B, 36, 1341-1342; Pnma, isostructural with Sm 5 Ge 4 ]. The structure contains two anionic moieties, i.e. Sb 4- 2 dumbbells [Sb-Sb 2.886 (3) A] and Sb 3- . The Sbl atom (Sb 3- ) lies inside a monocapped distorted trigonal prism (6 × Bal and 1 × Ba2). The Sb2 atom, which forms the Sb 4- 2 dumbbell, sits inside a tricapped trigonal prism (6 × Bal, 2 × Ba2 and 1 × Sb2).

Potassium barium bismuth oxide

KBa(4)Bi(3)O crystallizes in the centrosymmetric tetragonal space group I4/mcm. In this compound, bismuth is present as two anionic species, i.e. Bi(2)(4-) dumbbells [Bi-Bi 3.113 (3) A] and isolated Bi(3-). Atom Bi1 (Bi(3-)) lies inside a bicapped square antiprism (2 x K and 8 x Ba). Atom Bi2, which forms the Bi(2)(4-) dumbbell, sits inside a bicapped distorted trigonal prism (2 x K and 6 x Ba). O atoms occupy tetrahedral voids between Ba atoms.

Ba3TaAs3O displaying the distorted tetrahedral TaAs3O6- anion

The orthorhombic cell of tribarium tantalum arsenate, Ba 3 TaAs 3 O, contains pseudo-tetrahedral TaAs 3 O 6- anions surrounded by Ba 2+ cations. This forms a three-dimensional network of interconnected trigonal prisms. The compound is isostructural with Ba 3 NbAs 3 O and Eu 3 TaAs 3 O.