In-plane miscibility and mixed bilayer microstructure in mixtures of catanionic glycolipids and zwitterionic phospholipids.

SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) to establish the phase diagram. Gem16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed.

[Management of complicated retinal detachment using a heavy silicon oil as temporary tamponade]. / Tamponnement interne par huile de silicone lourde (Oxane Hd) dans les décollements de rétine complexes.

PURPOSE: To assess the efficacy and safety of a heavy silicon oil (a silicon oil-RMN3 mixture, a mixed fluorinated and hydrocarbonated olefin) as temporary internal tamponade in selected cases of retinal detachment with inferior breaks. PATIENTS AND METHODS: Forty-six patients were operated on (inferior and/or posterior breaks: 38; proliferative vitreoretinopathy > or =C2: 18; anterior proliferative vitreoretinopathy: 14), with a mean follow-up of 39 months. Seventeen patients were operated on with a heavy silicon oil of a 1.03 g/cm3 density and 29 patients with a silicon oil of a 1.02 g/cm3 density. Heavy silicon oil was removed in 41 patients after a mean of 9.3 weeks. RESULTS: Anatomic success was achieved in 35 cases after a mean follow-up of 39 months. Recurrent retinal detachment with proliferative vitreoretinopathy occurred in eight cases during heavy silicon oil tamponade. The removal was difficult in three cases with the 1.02 g/cm3 density silicon oil. Complications included glaucoma (eight eyes), major emulsification (two eyes), and an intraocular inflammation reaction to topical steroids (five eyes). CONCLUSION: Heavy silicon oil (Oxane Hd) is as safe and effective as standard silicon oil in the treatment of selected retinal detachment, but intraocular manipulations are quite difficult. A prospective study is necessary to compare the efficacy of Oxane Hd and standard silicon oil in selected cases of retinal detachment with inferior breaks and in cases of large inferior retinectomy.

A new long-chain UV absorber derived from 4-tert-butyl-4'-methoxydibenzoylmethane: absorbance stability under solar irradiation.

A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4'-methoxyphenyl)-propane 1,3-dione called C10-DBM, was prepared by grafting a ten-carbon aliphatic chain to the alpha-carbonyl position of 4- tert -butyl-4'-methoxydibenzoylmethane (BM-DBM).(1) UVA absorption efficiency of a cosmetic preparation containing this new filter, called C10-DBM, was tested and compared to an identical preparation containing BM-DBM. The two preparations were irradiated under a 150-W xenon lamp or exposed to natural sunlight. The originality of this new filter resided in that its UVA absorbance appeared during the irradiation of the molecule. Moreover, although the molar absorption coefficient of C10-DBM in the UVA domain was lower than that of BM-DBM, its absorption showed much more photostable behavior under both methods of irradiation. After two hours of sunlight exposure, the preparation containing the BM-DBM lost 85% of its UVA absorbance, whereas the UVA absorbance of the preparation containing C10-DBM showed a decrease of 3% in comparison to the maximum absorbance obtained after 30 minutes of irradiation. Also, after two hours of exposure to natural sunlight, the UVA absorbance of the preparation containing C10-DBM remained above its initial value (before the irradiation began).

Insulator semiconductor structures coated with biodegradable latexes as encapsulation matrix for urease.

A new urea biosensor for clinical applications was obtained by immobilization of urease within different latex polymers functionalized by hydroxy, acetate and lactobionate groups. Responses of these biosensors based on pH-ion-selective field effect insulator-semiconductor (IS) systems to urea additions were evaluated by capacitance measurements. UV-visible spectroscopy was used to check the urease activity in various matrixes. A good retention of the catalytic urease activity in the case of the cationic polymers was observed. In addition, rotating disk electrode experiments were carried out to determine the matrix permeability characteristics. Under optimal conditions, i.e. buffer capacity corresponding to 5 mM phosphate buffer, the urea enzyme insulator semiconductor (ENIS) sensors showed a linear response for urea concentrations in the range 10(-1.5) to 10(-4)M. Furthermore, kinetic parameters for the immobilized urease were obtained from Lineweaver-Burk plot. Clearly, a fast response and a good adhesion for the urease-acetate polymer composite films, prepared without using glutaraldehyde as cross-linking agent was observed.

The INSERM expert review on glycol ethers: findings and recommendations.

The use of glycol ethers and their effects on health have recently attracted the attention of the French health authorities. At their request, INSERM, the French Institute of Health and Medical Research, conducted a collective expertise review on glycol ethers in 1999. INSERM Expertise Reviews are independent procedures performed by experts from several disciplines, to guarantee the objectivity and the relevance of the report. During several work sessions, the experts carried out a critical analysis of and reviewed studies concerning the toxicity of glycol ethers. This process resulted in a series of recommendations and conclusions. All these data have been published in the form of a report and have been used to help the public authorities to make decisions on how to prevent risks for professionals and consumers.

Aggregation Behavior in Aqueous Solutions of a New Class of Asymmetric Bipolar Amphiphiles Investigated by Surface Tension Measurements.

Two series of amphiphilic derivatives of lactose have been synthesized. Tensiometric investigations of the critical micellar concentration (CMC) and the area per molecule at interface (calculated by the Gibbs equation) of aqueous solutions were performed. The values measured depend on the number of methylene groups of the alkyl spacer n and that of the side chain m as well as on the ionic strength and temperature. The results show a behavior closely related to that of gemini surfactants: (1) self-assembly phenomena occur at concentrations below 1 mM, (2) at constant n log CMC increases linearly with higher m, and (3) the influence of the temperature on the aggregation phenomenon is comparable. Copyright 2001 Academic Press.

Reactivity at the interface of chiral amphiphilic dendrimers. High asymmetric reduction by NaBH(4) of various prochiral ketones.

New amphiphilic dendrimers derived from PAMAM and D-gluconolactone were found to induce chirality in the reduction of prochiral ketones by NaBH(4), in heterogeneous (THF) and homogeneous (water) conditions. The third generation of these amphiphilic dendrimers, G(3)G, was found to be a good chiral ligand for the reduction of various prochiral ketones in heterogeneous conditions. Even with substrates well-known to give poor results (especially linear ketones), good enantioselectivities were obtained. It is also important to notice that under heterogeneous conditions (THF) the dendrimer could be recovered by filtration, regenerated, and recycled (up to 10 times), leading to reproducible results in asymmetric reduction of ketones. We have also discussed the reduction of acetophenone in water. Evidence is presented that the selectivity is dominated by the architecture of the dendrimer and some supramolecular ordering in the position of the ketone at the chiral solvating interface. The results obtained showed a correlation between stereoselectivity of the reduction and the compact character of the dendritic particles.

Chiral aggregates and asymmetric induction of the reduction of prochiral ketones.

The aim of this work was to establish structure-reactivity relationships between chiral aggregates (micelles, vesicles, and "pseudo-micelles" of amphiphilic dendrimers) and asymmetric induction. In water, micelles or vesicles formed with sugar-headed surfactants gave less than 10% ee in the reduction of prochiral ketones by NaBH(4), in contrast with dendrimers bearing the same types of sugar moieties, which gave more than 50% ee under the same reaction conditions. Moreover, in the presence of neoglycodendrimers in THF we have been able to improve reduction of prochiral ketones to give very high stereoselectivity, near 100% in many cases. Comparison of these results suggests that to improve high stereoselectivity it is necessary to work with rigid, well-organized colloidal objects. Copyright 2000 Wiley-Liss, Inc.

Cosmetic use formulations containing pentyl rhamnoside and cetyl rhamnoside.

For the first time, we report here the synthesis and use of pentyl and cetyl rhamnoside as cosurfactant or surfactant, respectively, and their evaluation in cosmetic formulations. l-rhamnose is more reactive than d-glucose in direct acetalization with long alkyl chains of alcohol, because of its higher lipophilicity, whereas for short alkyl chains, glucose and rhamnose are equivalent. Furthermore, pentyl rhamnoside could be used as a new non-toxic cosurfactant to formulate microemulsions. Finally, a white continuous aqueous phase emulsion and a liquid soap were evaluated for cosmetic uses. These new formulations showed very good cosmetic properties with high hydration properties and rapid cutaneous penetration.

A comparative physical study of two different hydrophilic synthetic latex matrices for the construction of a glucose biosensor.

Two different biodegradable latex polymers functionalised by hydroxy (1) or gluconamide (2) groups proved to be good immobilisation matrixes for glucose oxidase. The responses of these biosensors to glucose additions were measured by potentiostating the modified electrodes at 0.6 V/SCE in order to oxidise the hydrogen peroxide generated by the enzymatic oxidation of glucose in the presence of oxygen. The response of such electrodes was evaluated as a function of film thickness, pH and temperature. Rotating disk electrode experiments showed the influence of the enzyme on the structure of both latex films, namely a marked improvement in matrix permeability. The high permeability of the latex 1 based enzyme sensor (bilayer, P(m)=8.10x10(-4) cm s(-1)) resulted in a high dynamic range. Furthermore, the activation energy for a latex 1 sensor was determined to be 44.55 and 18.03 kJ mol(-1), respectively depending on the conformation of the enzyme.

Synthetic neoglycolipids for biological applications: correlation between their structures and their interactions with membrane proteins.

Synthetic glycolipids are of interest for their biological applications requiring interactions with membrane proteins. Depending on their structures, new series of glycolipids have applications in extraction of membrane proteins or medical applications as mimics of natural ligands of proteins.

Synthetic soluble analogs of galactosylceramide (GalCer) bind to the V3 domain of HIV-1 gp120 and inhibit HIV-1-induced fusion and entry.

Galactosylceramide (GalCer) is an alternative receptor allowing human immunodeficiency virus (HIV)-1 entry into CD4-negative cells of neural and colonic origin. Several lines of evidence suggest that this glycosphingolipid recognizes the V3 region of HIV-1 surface envelope glycoprotein gp120. Since the V3 loop plays a key role in the fusion process driven by HIV-1, we decided to synthesize soluble analogs of GalCer with the aim to develop a new class of anti-HIV-1 agents that could neutralize HIV-1 infection through masking of the V3 loop. We describe a short route, in three steps, for the synthesis of soluble analogs of GalCer, using unprotected lactose as the starting sugar. The analogs were prescreened in an assay based on the interaction between a V3 loop-derived synthetic peptide and [3H]suramin, a polysulfonyl compound displaying high affinity for the V3 loop. One of the soluble analogs, i.e. CA52(n15), strongly inhibited the binding of [3H]suramin to the V3 peptide, with an IC50 of 1.2 microM. This molecule was also able to inhibit [3H]suramin binding to recombinant gp120 with similar activity. Using a competition enzyme-linked immunosorbent assay with highly specific anti-gp120 monoclonal antibodies, the region recognized by CA52(n15) could be mapped to amino acids 318-323, which corresponds to the highly conserved consensus motif GPGRAF. Interestingly, the region recognized by suramin, i.e. IQRGP-R-F, was partially overlapping this motif. CA52(n15) was able to inhibit HIV-1-induced cell fusion as well as HIV-1 entry into both CD4(+) and CD4(-)/GalCer+ cells. A structure-activity relationship study showed that: (i) the antiviral activity of soluble analogs of GalCer correlates with V3 loop binding, and (ii) the hydrophobic moiety of the molecule plays an important role in this activity. Taken together, these data show that synthetic analogs of GalCer can inhibit HIV-1 entry into both CD4(-) and CD4(+) cells through masking of the V3 loop.

Microemulsions of perfluorinated and semi-fluorinated compounds.

Perfluorocarbons combine high gas dissolving capacities with extreme chemical and biological inertness: they are good oxygen carriers in artificial blood and in liquid breathing. However fluorocarbons are highly hydrophobic molecules. To solve the problem of their transport, it is necessary to use the perfluorocarbons as an oil-in water emulsion (O/W). To avoid harsh treatment to form such emulsions and in order to have injectable "blood substitutes", microemulsions seem particularly attractive since they are fluid, transparent, thermodynamically stable microheterogeneous systems. Microemulsions, contrarily to classical emulsions, are formed spontaneously by adding suitable surfactants (or a surfactant+a cosurfactant) in appropriate proportions to a non miscible mixture of water and oil. Biocompatible O/W microemulsions are difficult to obtain because of: 1) the existing segregation between perfluorinated and hydrogenated chains, resulting, in some cases in heterogeneities or gelation phases; 2) the toxicity of some components; 3) the possible harmfulness of the dispersed system, etc... We'll discuss all the parameters involved of the microemulsification process, the nature of products, the phase diagrams, and the phase behaviors. This study will outline certain guidelines necessary for the formation of microemulsions of perfluorinated (or almost completely fluorinated) oils with perfluorinated (or partially fluorinated) surfactants.