Determination of DMPC hydration in the Lα and Lβ′ phases by 2H solid state NMR of D2O

AbstractThe number of water molecules bound to the dimyristoylphosphatidylcholine (DMPC) interface was investigated both in the fluid (Lα) and gel (Lβ′) phases by solid state deuterium NMR of D2O. We determined that each DMPC molecule binds 9.7±0.5 and less than 4.3±0.5 D2O in the fluid and gel phases respectively. These results are accounted for by considering the number of DMPC binding sites as well as the molecular organization in each phase. ©1997 Federation of European Biochemical Societies

Encapsulation of epsilon-Viniferin into Multi-Lamellar Liposomes: Development of a Rapid, Easy and Cost-Efficient Separation Method to Determine the Encapsulation Efficiency

Onion-type multi-lamellar liposomes (MLLs), composed of a mixture of phosphatidylcholine and Tween 80, were analyzed for their ability to encapsulate epsilon-Viniferin (epsilon Vin), a resveratrol dimer. Their encapsulation efficiency (EE) was measured by UV-VIS spectroscopy using three different separation methods-ultracentrifugation, size exclusion chromatography, and a more original and advantageous one, based on adsorption filtration. The adsorption filtration method consists indeed of using syringe filters to retain the molecule of interest, and not the liposomes as usually performed. The process is rapid (less than 10 min), easy to handle, and inexpensive in terms of sample amount (around 2 mg of liposomes) and equipment (one syringe filter is required). Whatever the separation method, a similar EE value was determined, validating the proposed method. A total of 80% +/- 4% of epsilon Vin was found to be encapsulated leading to a 6.1% payload, roughly twice those reported for resveratrol-loaded liposomes. Finally, the release kinetics of epsilon Vin from MLLs was followed for a 77 day period, demonstrating a slow release of the polyphenol

Superhydrophobic, highly adhesive arrays of copper hollow spheres produced by electro-colloidal lithography

We report the patterning of copper surfaces which display both superhydrophobicity and high adhesion thanks to a new feature geometry, and without resorting to chemical modification. Polystyrene beads organized in 2D crystals under an AC electric field act as a template for the growth of copper deposited via cupric ion-loaded multi-lamellar vesicles. After the removal of the beads, hexagonal arrays of supported hollow spheres or copper bowls are generated, depending on the amount of deposited copper. While the bowl-covered surfaces display a predictable decreasing wettability (Cassie model) as their wall height increases, the hollow sphere-covered surfaces exhibit both high adhesion and superhydrophobicity (Cassie-Baxter state)

Electro-colloidal lithography: a versatile approach combining colloidal particles and electrical fields for the fabrication of patterned polymer and metal films

We report a new soft lithography approach which only requires colloidal particles and tension generators. This process, named electro-colloidal lithography, is based on the behavior of colloidal assemblies submitted to electric fields generated by alternative current (AC) and direct current (DC). Its advantages are its low cost, fastness and easiness. As an illustration, hexagonal arrays of metal nano-rings, and hexagonal arrays of conductive holes into a contiguous or particle-made polymer matrix were produced. We show how to control separately and finely both the inter-structure separation and the structure morphology (diameter, height, thickness) in a very simple manner. Commercial colloidal particles (polystyrene beads) and synthesized colloidal particles (surfactantmade multilamellar vesicles) were both successfully tested for surface patterning showing the universality/adaptability of this technique

Incorporation de nanoparticules inorganiques dans des vésicules multilamellaires lipidiques de type "oignon"

Ce travail de thèse a porté sur l'incorporation de nanoparticules inorganiques au sein de vésicules multilamellaires lipidiques de type "oignon" La synthèse intravésiculaire de nanoparticules d'or a été réalisée par voie chimique, photoréduction UV et radiolyse gamma. Nous avons montré qu'il est possible de contrôler la morphologie des particules par la composition vésiculaire dans le cas d'une réduction chimique. Quelle que soit la voie de synthèse, nous avons établi que la stabilité de l'oignon dépend de la taille des nanoparticules qu'il contient et de leur nombre. L'utilisation de ces structures hybrides, oignons/nanoparticules (or et argent), pour la catalyse supportée a été abordée. Nous avons également élaboré des oignons magnétiques selon deux voies : par synthèse intravésiculaire de nanoparticules magnétiques et par encapsulation d'un ferrofluide. Les propriétés des oignons en terme de magnétisme, d'hyperthermie magnétique et d'agents de contraste pour IRM ont été étudiées.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Polypyrrole-glucose oxidase biosensor Effect of enzyme encapsulation in multilamellar vesicles on analytical properties

In this paper, we present the analytical properties of a new type of polypyrrole-based, enzymatic amperometric biosensor. It is produced by encapsulating the enzyme, glucose oxidase (GOx), into onion-type multilamellar vesicles (MLV).We compare its properties to those of a classical GOx–polypyrrole biosensor. When MLV are used to embed GOx in polypyrrole (PPy), GOx behaves as a Michaelis–Menten enzyme. Without MLV, a deviation to the Michaelis–Menten behaviour is observed for high glucose concentrations. Kinetics parameters of both types of biosensors are studied as a function of the surface charge synthesis: GOx encapsulation induces a 200-fold increase of the apparent maximal current (Iappm ) and a 10-fold increase of the apparent Michaelis constant (Kappm). Sensitivity is improved by a factor of 5. GOx is also shown to be less sensitive to inhibiting ions (Cl−) when MLV are used. A residual amperometric response of 43% instead of 3% is measured. Finally, the long-term stability of biosensors is improved by the GOx encapsulation. All these results are partially explained by our previous study on the morphology of PPy films fabricated with GOx encapsulated into onion-type MLV (Olea et al., 2007)

Arrays of copper rings with tunable dimensions via electro-colloidal lithography

Electro-colloidal lithography (ECL) is an easy, fast, straightforward and cheap patterning process that has been used here to design patterned copper film. ECL consists in assembling polystyrene (PS) micro-beads in 2D hexagonal crystals onto an electrode using AC (Alternative Current) electric field, in sticking them onto the electrode surface where copper is then deposited using Cu2+-containing multi-lamellar vesicles (MLVs) submitted to a DC (Direct Current) electric field. Copper rings are then formed; their separation, ranging from 2 to 4.2 mu m, could be varied playing on either PS beads size or on AC electric field parameters (frequency and amplitude). The ring internal diameter (100-880 nm range), the ring height (28-400 nm range) as well as the copper film thickness (6-102 nm range) were controlled through the time of DC field application. AFM, SEM, microscopic imaging as well as mathematical modeling show that PS beads behave as a template for copper ring growth, and that this patterning is due to an accumulation of MLVs around the dielectric PS spheres on the electrode. (C) 2015 Elsevier B.V. All rights reserved

Polypyrrole-glucose oxidase biosensor. Effect of enzyme encapsulation in multilamellar vesicles on film growth and morphology

We describe the making of a polypyrrole (PPy)/glucose oxidase (GOx) film using onion-type multilamellar vesicles (MLV) to transport and incorporate the enzyme in the polymer film. The morphology of the film is studied as a function of the synthesis charge by fluorescence microscopy (AFM). Electrochemical analysis shows that encapsulating the enzyme removes the negative influence of GOx on the film growth rate. On the contrary, GOx-containing MLV are shown to act as dopant for the PPy synthesis, drastically increasing the film synthesis rate. Another advantage using MLV for GOx insertion into PPy film is to induce reproducible growth kinetics, while unpredictable kinetics are found with free GOx. Such result is explained by different nucleation mechanisms

Carbohydrate Polymers

In this paper, we propose both a new application for cellulose micro-beads and a new concept in colloidal lithography to directly deposit and template a metal from ions transported by the organized colloidal particles, using the colloidal particles themselves. To do so, 5 μm-sized cellulose micro-beads (CμBs) were first surface-functionalized by trimellitic anhydride to introduce carboxylate ligands before decorating them with Cu2+ ions by complexation of the carboxylate groups with a CuCl2 solution. The Cu2+-loaded CμBs, dispersed in an aqueous phase, were organized in compact monolayer at the vicinity of a planar electrode. The release of cupric ions and subsequent copper deposition were triggered by an electric field delivered by a tension generator. 2D non-close-packing arrays of copper dots assemblies displaying hexagonal symmetry were generated below or around the micro-beads – depending on the ions concentration in the aqueous phase – leading respectively to copper dots deposited circularly or concentrated in rings. The Cu2+-loaded cellulose beads allowed the covering of 2 cm²-surfaces by copper patterns in less than 45 min, using an easy and cheap process