Cationic detergent/sterol mixtures can form fluid lamellar phases and stable unilamellar vesicles.

In recent studies, it has been shown that mixtures of palmitic acid (PA), and cholesterol or cholesterol sulfate (Schol), in a PA/sterol molar ratio of 30/70 lead to the formation of liquid-ordered (lo) lamellar phases. The extrusion of these systems gave large unilamellar vesicles (LUVs) that displayed a very limited passive permeability, a property associated with their high sterol content. In this study, we showed that the formation of lo-phase bilayers was also possible when mixing a cationic detergent (cetylpyridinium chloride, CPC) and sterol in a 30/70 molar ratio. The existence of this phase was established using IR and 2H NMR spectroscopy. Moreover, 2H NMR allowed us to study the orientation and dynamics of CPC and cholesterol in these self-assemblies. The extrusion of the CPC/Schol bilayers leads to the formation of LUVs, and their passive permeability was found to be very limited, making them interesting candidates as nanovectors.