Robert Coudert

Ion solvation in carbonate-based lithium battery electrolyte solutions

Partial molar volumes at infinite dilution VMX∞ of three electrolytes (LiClO4, LiCF3SO3 and LiPF6) have been determined by vibrating-tube densimetry in pure propylene carbonate (PC), ethylene carbonate (EC) and dimethylcarbonate (DMC) and, for LiClO4, in some mixtures of EC with DMC and PC. Vmx∞ are strongly dependent of the nature of the pure or mixed solvents. Absolute ionic molar volumes of the Li ion and associated anions have been deduced from the partial molar volume of tetra-alkylammonium salts in the same solvents. For this purpose the concept of van der Waals volume and packing density proposed by King has been employed. In all solvents under investigation, the volume of the Li ion has similar values: VLi+∞ ≈ 5 cm3/mol. This result is different from what is obtained using the tetraphenylarsonium tetraphenylborate assumption. The differences among polyatomic anions volumes are greater than expected and strongly dependent on the solvents nature. These effects are discussed in terms of ion-solvent interactions: ion solvation, packing effect in the solvation shell and electrostriction. Implication of these findings for Li batteries is briefly discussed.

Cellular Pathway of Plasmids Vectorized by Cholesterol-based Cationic Liposomes

We investigated by transmission electron microscopy the cellular route in tumor MCF7 cells of DNA labeled with digoxigenin, carried by cationic liposomes (Lip+) prepared from TMAEC-Chol [3β(N-(N,N,N-trimethylaminoethane)-carbamoyl)cholesterol iodide] and TEAPC-Chol [3β(N-(N,N,N-triethylaminopropane)-carbamoyl)cholesterol iodide], two cholesterol-based cationic lipids containing a quaternary ammonium. In a previous work we showed the pathway of cationic lipid/plasmid complexes from the beginning of endocytosis until their entry into the perinuclear area. Beyond this limit, unlabeled exogenous plasmids cannot be distinguished with nuclear DNA. This work dealt with the cellular fate of cationic liposome-vectorized plasmids labeled with digoxigenin using an immunogold procedure. Early after the beginning of transfection (30 min, 1 hr, 5 hr), gold particles were observed only in the cytoplasm and in endosome-like vesicles, whereas after 24 hr gold particles were densely present in the nucleus. These results demonstrate the nuclear localization of plasmids vectorized by the cationic liposomes used. The results are discussed in comparison with transfection efficiency measurements.

Nouveau procédé de synthèse de l'hexafluorophosphate de lithium

Abstract Lithium hexafluorophosphate (LiPF 6 ) has been synthesized using commercial hexafluorophosphoric acid (HPF 6 ) as starting material. The neutralization of this acid monitored by conductimetry by lithium hydroxide in aqueous, alcoholic and acetonitrile media gives LiPF 6 with yields of 42, 35 and 61% respectively. This salt may also be prepared by neutralizing similarly lithium hydroxide (LiOH) by pyridinium hexafluorophosphate (C 5 H 5 NHPF 6 ) obtained by reaction from equimolar amounts of pyridine and HPF 6 in alcoholic media (yield about 90%). From C 5 H 5 NHPF 6 a new synthesis leads to LiPF 6 in two steps. First the reaction of C 5 H 5 NHPF 6 with ROLi (R = CH 3 , C 2 H 5 ) in methyl or ethyl alcohol, acetonitrile and tetrahydrofuran media or with RLi (R = C 4 H 9 , tert -butyl) in pentane or hexane, gives lithium pyridinium hexafluorophosphate Li(C 5 H 5 N)PF 6 in about 95% yield. Heating this at 30–50 °C under vacuum gives LiPF 6 with a purity determined by lithium titration of about 99%.

Inhibition of VEGF expression in A431 and MDA-MB-231 tumour cells by cationic lipid-mediated siRNA delivery.

In order to promote siRNA transfer in tumour cells, we used an original cationic lipid, synthesized in our laboratory, dimethyl-hydroxyethyl-aminopropane-carbamoyl-cholesterol (DMHAPC-Chol). Liposomes were prepared from this lipid and dioleoylphosphatidylethanolamine (DOPE) in equimolar proportion. Its transfecting capacity was evaluated using ELISA, cell cytometry, and RT-PCR in estimating the silencing effect of VEGF siRNA. This liposome efficiently delivered VEGF siRNA in two human cancer cell lines abundantly secreting VEGF, A431 and MDA-MB-231. Results showed that 50 nM of VEGF siRNA carried by DMHAPC-Chol/DOPE liposomes already silenced more than 90% of VEGF in these cells. A comparative study with two commercial carriers indicated that the inhibition induced by VEGF siRNA transported by cationic DMHAPC-Chol/DOPE liposomes was comparable to that induced by INTERFERin and better than lipofectamine 2000. Moreover, a transfection by a GFP plasmid followed by a GFP siRNA showed that DMHAPC-Chol/DOPE liposomes compared to lipofectamine were less efficient for plasmid but better for siRNA transport. Following one of our previous works concerning cell delivery of plasmid (), the main interest of results presented here resides in the double potential of DMHAPC-Chol/DOPE liposomes to deliver little-sized siRNA as well as large nucleic acids in cells.

Aggregation of new bipolar glucosyled and cationic fluoroamphiphiles in aqueous media

A new series of N-[3-(trimethylamino)propyl]-perfluoro-N-glucosyl amide-Iodides, differing by the length of the fluorocarbon tail (7, 9, and 11), have been synthesized in three steps involving unprotected glucose, N,N-dimethyl-1,3-propane diamine, the appropriate methyl-perfluoroalcanoate, and methyl iodide. Their aggregation and surface properties were studied in aqueous solution using conductivity, surface tension, and dynamic light scattering measurements. The critical micelle concentrations (CMC), the micellar aggregation numbers, the geometric packing parameters, the area/surfactant molecule at the interface, the surface excess concentration, the micellar ionization degree β, and the free energies of micellization have been investigated. DLS results show various morphologies of aggregates such as micelles and vesicles according to the increase in the hydrophobic chain length.

A comparative study of micellization with fluorinated and hydrogenated diquaternary ammonium bolaamphiphiles

Two new N(a),N(b)-Bis[3-(trimethylamino)propyl]-perfluoroalkanes diamide-Iodide with (a=1; b=10) and (a=1; b=12), differing by the fluorocarbon tail spacer (8 or 10 CF2), and the N(1),N(12)-Bis[3-(trimethylamino)propyl]-dodecanediamide-Iodide have been synthesized in two steps involving the appropriate dimethyl perfluoro or hydrogeno alkane dicarboxylate, N,N-dimethyl-1,3-propane diamine, and methyl iodide. Their surface properties were studied at 45°C in aqueous solutions using conductivity, surface tension, and dynamic light scattering (DLS) measurements. A comparison of the micellar parameters usually obtained by these techniques has been carried out. The critical micelle concentrations (CMCs), the geometric packing parameters, the surface excess concentration, the area/surfactant molecule at the interface, the micellar ionization degree β and the free energies of micellization, the diffusion coefficient, and the hydrodynamic diameter were discussed. The effect of added KI on these parameters and on the size and on the kind of aggregates has been also investigated. The addition of 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) to the surfactant solutions, where the size of the complex DOPE-surfactant was determined by DLS over a wide range of concentrations, reveals a very different behavior comparing fluorinated and hydrogenated compounds.

Chapter 5: Cationic Liposomes as Transmembrane Carriers of Nucleic Acids

Abstract Cationic liposomes constitute a new class of bilayer, which are able to form complexes with nucleic acids (DNA or RNA), help to cross the cellular membranes, and then deliver them into cells. This interesting property opens several applications for cationic liposomes, in particular in gene therapy, vaccination and biotechnology. The aim of this chapter is to review the structural properties of these liposomes and to describe the methods of characterization as well as methods to observe their pathway in cells after the passage through the cellular barrier. After the description of chemical structures of cholesterol-based cationic lipids investigated in our laboratory, their formation into liposomes, their interaction with nucleic acids and the internalization of complexes in cells will be dealt with. The cytotoxicity and the transfection level are outlined, and applications of cationic liposomes for transfer of interest DNA are illustrated.

Synthesis and physicochemical properties of unsaturated trifluoromethylated sodium carboxylates in aqueous media

Structural modifications of unsaturated sodium carboxylate surfactants in terms of trifluoromethylation associated with the hydrocarbon chain length have been studied, the synthesis is described, and aggregation properties have been examined by conductimetry and vapor pressure osmometry between 30°C and 45°C. No strong effect of adding a CF3 group was observed on the Critical Micellar Concentrations. However, the thermodynamic study shows the specific effect exerted by the CF3 group through the enhancement of the entropic contribution.