Synthesis of versatile chemical tools toward a structure/properties relationships study onto targeting colloids.

As part of a drug delivery project, four aldehydes of the type Pam-Lys(Pam)-spacer-CO-CHO were synthesized to be included in targeting colloids. Though amphiphilic, they were obtained within reasonable yields (18-55%) and with high RP-HPLC purity ( approximately 90%). Parallely, six complementary targeting peptides of the type H(2)N-NH-CH(2)-CO-spacer-YGRGDSP-NH(2) were prepared to be anchored onto colloids. Isolated yields are related to the spacer length and nature. To easily and rapidly modulate the distance between the peptide and the vesicle, every partners were elaborated on solid phase and the expected constructions were obtained by hydrazone ligation. One possible application is presented here with multilamellar vesicles targeting HUVEC cells. Preliminary results prove that the fine-tuning of the spacer length permits to optimize the recognition toward the target cells.

Amplification of antibody responses to antigen using small multilamellar vesicles for delivery system.

New vaccines based on subunits, synthetic peptides, or DNA need innovative adjuvants or antigen delivery systems: Spherulites are multilamellar vesicles made of incompatible lipid bilayers without any aqueous core. In this study, we evaluated their ability to induce immune responses against human serum albumin (HSA). Mice were immunized by the intraperitoneal/intravenous route or subcutaneously with HSA without any adjuvant or in its encapsulated form. We showed that Spherulites strongly enhanced the seric antibody responses and led to a mixed isotypic distribution characterized by an IgG(2a) potentiation. This demonstrated that Spherulites can improve the presentation of weak antigens to the immune system.

DNA intercalation in neutral multilamellar membranes.

We report a small angle X-ray scattering study of the DNA/neutral lipid/water system showing that it is possible to confine DNA into a neutral multilamellar phase at high lipid-to-DNA weight ratio, despite the lack of electrostatic interactions in this system. This phase is characterized by a 2D ordering of the DNA molecules intercalated between the neutral bilayers of a 3D smectic phase as shown from the presence of a DNA-DNA correlation peak and the 1D electron density profile of the multilamellar phase. We further demonstrate that it is possible to disperse this phase as small multilamellar vesicles encapsulating high amounts of DNA.

Grafting of synthetic mannose receptor-ligands onto onion vectors for human dendritic cells targeting.

A practical preparation of onion vesicles targeted to dendritic cells involves the grafting of mannose-mimetic clusters, bearing a hydrazino group, onto the surface of onion vesicles containing an aldehyde functionalized lipid.

Dynamical behavior of a complex fluid near an out-of-equilibrium transition: approaching simple rheological chaos.

We report here an extensive study of sustained oscillations of the viscosity of a complex fluid near an out-of-equilibrium transition. Using well defined protocols, we perform rheological measurements of the onion texture near a layering transition in a Couette flow. This complex fluid exhibits sustained oscillations of the viscosity, on a large time scale (500 s) at controlled stress. These oscillations are directly correlated to an oscillating microstructural change of the texture of the fluid. We observe a great diversity of dynamical behavior and show that there is a coupling with spatial effects in the inverted Delta v direction. This is in agreement with a careful analysis of the temporal series of the viscosity with the dynamical system theory. This analysis indicates that the observed dynamical responses do not strictly correspond to three-dimensional chaotic states, probably because some spatiotemporal effects are present and are likely to play an important role.

Modeling leakage kinetics from multilamellar vesicles for membrane permeability determination: application to glucose.

The glucose permeability of bilayers formed from phosphatidylcholine, Brij30, and sodium octadecyl sulfate has been determined via an enzymatic reaction. Glucose is encapsulated in either uni- or multilamellar vesicles (MLV) and its concentration in the dispersion medium is monitored by spectrophotometry analysis through the rate of glucose oxidase-catalyzed reaction of glucose oxidation. A kinetic model of leakage, taking explicitly into account one, two, or n(w)-walls (n(w) >> 1) for the vesicles and assuming an enzymatic Michaelis-Menten behavior, is proposed and used to fit the experimental data. The two-wall model was chosen to fit experimental data obtained on MLV since an average value of 1.7 bilayers was estimated for MLV by cryo-TEM imaging. A permeability value of 5.8 +/- 4.4 10(-9) cm/s was found. The proposed model is validated by the measurement of the bilayer permeability deduced from the modeling of glucose leakage from unilamellar vesicles with the same composition. In this latter case, a value of 8.3 +/- 0.7 10(-9) cm/s is found for the permeability, which is within the error bar of the value found with MLV.