(535e) Kinetics of Phospholipid Transport to Fluid Interfaces in an Aqueous Dispersion or Laponite Gel

Dynamic surface tension measurements were used to track adsorption kinetics for dilauroyl phosphatidylcholine (DLPC) or dimyristoyl phosphatidylcholine (DMPC) from monodisperse vesicle dispersions to an air-water interface. Our goal was to probe the role of diffusion of vesicles and dissolved lipid monomer, interfacial adsorption, and release of lipid monomers from vesicles, on the adsorption mechanism. We have examined adsorption dynamics at different temperatures, vesicle diameters and in the presence or absence of convection to explore these effects on the controlling pathway (via direct vesicle transport and adsorption, or via transport as dissolved monomer) and the steps within. At sufficiently high vesicle concentrations (≥0.25mM for DLPC and ≥1mM for DMPC), the kinetics were found to be controlled by monomer diffusion coupled to the rate of monomer release from vesicles, and not to depend on rates of direct vesicle diffusion or interfacial adsorption. At lower vesicle concentrations, however, vesicle diffusion limitations complicate the dynamics. To probe these vesicle diffusion limitations, we dispersed DLPC vesicles into a suspension of Laponite clay nanoparticles, with the latter matrix acting to arrest the vesicles (prevent vesicle diffusion) while allowing for free monomer diffusion. Laponite suspensions can form a fluid gel over time that limits diffusion based on particle size (i.e. vesicles vs. monomers).¹ By preventing vesicle diffusion, the transport pathway of the monomer can be made transparent, allowing us to gain insight into rate-limiting steps within the adsorption pathway, and to clarify any effects of vesicle diffusion.

1. Petit, L.; Barentin, C.; Colobani, J.;Ybert, C.; Bocquet, L. Langmuir2009, 25, 12048‒12055.