Preparation and Structural Characterization of Different Cholesterol-CTAB Supramolecular Assemblies Using CO2-expanded Solvents

Nanoscopic and uniform unilamellar vesicles, rich in cholesterol, have been prepared using CO2-expanded solvents. This procedure is based on the depressurization of a cholesterol solution in CO2-expanded acetone into an aqueous solution containing a surfactant. The CO2 is used here as a co-solvent, allowing the straightforward preparation of vesicular systems with controlled size distribution, uniform shape, and stability unachievable by conventional mixing technologies. The analysis of the different CTAB/cholesterol assemblies that can be formed by the tuning of CTAB/cholesterol molar ratios is crucial regarding the capacity of vesicles as intelligent drug biovectors. For this purpose, playing with operational parameters and surfactant/lipid ratios, we have been able to prepare different CTAB/cholesterol assemblies in a robust way, and characterize them by dynamic light scattering (DLS), ζ potential and cryogenic transmission electron microscopy (cryo-TEM).