Nanovesicles Based on Mixtures of a Biantennary Glycolipid with Ionic Co-Surfactants

A biantennary surfactant based on a synthetic C₁₆-maltoside was chosen to prepare vesicles for a potential vesicular drug delivery system. The synthesis comprised of three stages: Initial synthesis of β-d-maltose octaacetate was followed by glycosidation of 2-hexyl-decanol and final glycolipid deacetylation. Both α- and β-anomers were prepared and their anomeric purity was evaluated by ¹H NMR. Owing to the low water solubility of the glycolipid, addition of ionic co-surfactants was believed to promote the surfactant distribution, thus leading to smaller and more uniform vesicles. The assembly behavior of the surfactant systems was studied by contact penetration under an optical polarizing microscope, while interfacial properties were determined by surface tension measurements. Vesicles were prepared by injection of an ethanolic solution into bulk water and investigated by dynamic light scattering and field emission scanning electron microscopy. Contact of the surfactant mixtures with water indicated a high tendency to exhibit the lamellar phase and confirmed the expected low molecular solubility. These findings suggest a potential of the surfactant to form stable vesicles. Injection of an ethanolic surfactant solution into bulk water gave sub-micrometer sized vesicles with a narrow size distribution. Application of ionic co-surfactants reduced the vesicle size. In particular ∼20 % of anionic SDS proved highly effective, lowering the vesicle size by nearly one decade, thus accessing nano-sized vesicles. Encapsulation of a water-soluble drug was achieved in a 76 ± 10 % efficiency.