Quatsomes: highly stable nanovesicles formed by sterols and quaternary ammonium surfactants

N. Ventosa, L. Ferrer-Tasies, E. Moreno-Calvo, M. Cano-Sarabia, M. Aguilella-Arzo, A. Angelova, S. Lesieur, S. Ricart, J. Veciana, J. Faraudo

Keywords: nanovesicle, self-assembling, cationic surfactants, cholesterol, molecular dynamic simulation


Thermodynamically stable nanovesicular structures are of high interest for academia and industry in a wide variety of application fields, ranging from nanomaterials preparation to nanomedicine. Here we show the ability of quaternary ammonium surfactants and sterols to self-assemble forming stable amphiphilic bimolecular building-blocks with the appropriate structural characteristics to form, in aqueous phases, closed bilayers, named quatsomes, with outstanding stability with time and temperature. Molecular self-assembling of cholesterol (Chol) and surfactant cetyltrimethylammonium bromide (CTAB) was studied by quasi-elastic light scattering (QELS), cryogenic transmission electron microscopy (cryo-TEM), turbidity (optical density) measurements and molecular dynamic simulations (MD) with atomistic detail, upon varying the cholesterol-to-surfactant molar ratio. As pure species, CTAB forms micelles and insoluble cholesterol forms crystals in water. However, our molecular dynamic simulations reveal that the synergy between CTAB and cholesterol molecules makes them self-assemble into bimolecular amphiphiles and then into bilayers in the presence of water. These bilayers have the same structure of those formed by double tailed unimolecular amphiphiles.