Structure and phase behavior of phospholipid-based micelles in nonaqueous media

The phase behavior of phospholipid aggregates in nonaqueous media of hexane and vegetable oil with a negligible aqueous core (water < 0.3 wt %)was investigated. It was found that inverse micellar structures formed by phospholipids in a hexane-oil mixture resulted in three principal domains of phase behavior: micellar solution, two-phase dispersion, and dense micellar solution. The dependence of the phases on temperature, water, and solvent/phospholipid concentration was also examined. As opposed to structures in aqueous media, nonaqueous structures were found to be weakly dependent on these parameters, with the exception of solvent composition. Micellar sizes (similar to 60 Angstrom diameter) were determined using various experimental techniques. The principal techniques used in our studies were cryo-transmission electron microscopy, dynamic light scattering, and X-ray scattering. In our studies, we explored the limitations of these techniques and estimated size, shape, and phase nature of lipid aggregates.