We applied a time-resolved small-angle neutron scattering technique to the vesicle system of dimyristoylphosphatidylcholine for the first time to determine lipid kinetics. The observed kinetics could be explicitly represented by a simple model that includes two independent kinetic parameters, i.e., the rates of transbilayer and interbilayer exchange. This technique is perfectly suited for the determination of lipid exchange kinetics in equilibrium and applicable to evaluation of the activity of the factors relevant to lipid migration, such as translocase and lipid transfer proteins.
Aqueous dispersions of lyotropic liquid crystalline phases (cubosomes and hexosomes) were prepared using lipid mixtures, monoolein (MO) and oleic acid (OA), and emulsifier Pluronic F127 by changing their composition. The size and internal structure of the prepared particles were characterized by dynamic light scattering and small-angle X-ray scattering, respectively. At the weight ratio of MO:OA ) 5:5 and 8 wt % F127 to the total lipid mixtures, particles with a diameter of ca. 140 nm and including an inverted hexagonal (HII) phase were formed. With an increase in the F127 concentration, the particle size decreased, but the internal structure (lattice constant) did not change, suggesting that F127 absorbs at the particle surface with little incorporation in the HII phase. The lipid ratios and solvent pH strongly affected the morphology of the internal structure of the particles. By increasing the weight fraction of OA in the lipid mixtures, the internal structure transformed in the order of bicontinuous cubic-inverted hexagonal-inverted cubic. In addition, transformation from the cubosome to the hexosome was observed by decreasing the pH, suggesting that the interior of the nanoparticles is responsive to the outer environment.
A novel aqueous dispersion of particles with bicontinuous cubic phases in their interior (cubosomes) was
prepared. A nonionic triblock copolymer, Pluronic F127, was used as an emulsifier of a liquid crystal phase
of hydrated monoolein (MO). Dynamic light scattering showed that particles with an average diameter
of 160−270 nm were formed by high-pressure emulsification. Particle size decreased as the weight ratio
of F127 to MO increased up to 10%, whereas it was constant at higher than 10%. Small-angle X-ray
scattering experiments confirmed the presence of two kinds of cubic structures (CD and CP). At 3% F127,
the diffraction pattern corresponding to the CD was dominant and the diffraction of the CP was minimally
detected, suggesting that the polymer preferably emerges to the surface of the particles and the interior
has a CD structure consisting mostly of hydrated MO. The proportion of the CP increased with F127
content, which suggests that preferentially concentrated F127 at the surface participates in the formation
of the CP phase. 13C NMR experiments with a paramagnetic shift reagent showed that the signal of the
carbonyl carbon of oleic-1-13C acid mixed in the particles readily shifted to a lower magnetic field by
addition of europium ion (Eu3+), indicating high accessibility of the ion into the water channel inside the
particles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.