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The effect of β-sitosteryl sulfate (PSO 4) on the liposomal size, stability, fluidity, and dispersibility of DPPC liposomes prepared by vortex mixing, bath-sonication, and probe-sonication has been studied. PSO 4 significantly decreases the particle size of the multilamellar liposomes (MLVs). The sizes of the vortexmixed and the bath-sonicated liposomes vary as a function of PSO 4 concentration. On the other hand, PSO 4 has only little effect on the particle sizes of probe sonicated liposomes. In some cases, the liposomal stability at higher PSO 4 concentrations depends on the preparation method. PSO 4 improves the dispersibility of the DPPC liposomes and enhances their hydration. It also increases the fluidity of the liposomes prepared by each method. Our results suggest that liposomes consisting of DPPC and PSO 4 can be suitable as a cosmetic or pharmaceutical ingredient for the effective delivery of the active components into the body.

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The microstructures in dilute aqueous solutions of the ditetradecyldimethylammonium surfactant cation with mixtures of bromide and acetate counterion were studied by using video-enhanced microscopy, video-enhanced microelectrophoresis, cryotransmission electron microscopy, and time-resolved fluorescence quenching. A gradual transformation from multilamellar liposomes to, first, unilamellar vesicles and microtubules and, second, small spherical micelles was seen when the bromide-to-acetate ratio was reduced from large values to zero. Fluorescence quenching reveals that micells and larger aggregates (i.e., microtubules and vesicles) coexist at intermediate bromide-to-acetate ratios. Electron micrographs of these systems at low bromide-to-acetate ratios reveal the presence of single-component spherical micelles and confirm the ability to image micelles. The results can be explained in terms of increased head-group and interaggregate repulsions as the bromide ion is replaced by the highly hydrated acetate ion.