Molecular arrangements and interconnected bilayer formation induced by alcohol or polyalcohol in phospholipid vesicles

A self-assembled hybrid phospholipid vesicular system containing various penetration enhancers – ethanol, Transcutol and propylenglycol – was prepared and characterized. The effects of the different alcohol or polyalcohols structure and their concentration on the features of the assembled vesicles were evaluated using a combination of different techniques, including cryo-transmission electron microscopy, laser light scattering, differential scanning calorimetry, small- and wide-angle X-ray scattering and rheological analysis. These techniques allow explaining the structural rearrangements of the bilayer assembly due to the alcohol or polyalcohol addition. X-ray scattering studies showed that such addition at the highest concentration (20%) allowed structure modification to oligolamellar vesicles and a bilayer transition to interdigitated phase. Rheological studies confirmed the importance of alcohol or polyalcohol in the structuring dispersions probably due to a partial tilting of phosphatidylcholine acyl chains forming interdigitated and interconnected bilayer vesicles.