Stability of cubic phase and curvature tuning in the lyotropic system of branched chain galactose-based glycolipid by amphiphilic additives

Abstract

Inverse bicontinuous cubic phases are among the most suitable nanostructures used as carriers of drugs, diagnostic agents, and as templates for crystallization of membrane protein. The versatility of their highly ordered internal nanostructures with large interfacial areas make them capable to accommodate hydrophobic, hydrophilic or amphiphilic guest molecules and specifically active pharmaceutical ingredients. Previous studies have shown that pure sugar-based lipid namely 2-hexyl-decyl α-D-galactopyranoside (α-Gal-OC10C6) self-assemble into bicontinuous cubic phases of gyroid type (Ia3d) at low water content and of the diamond type (Pn3m) in excess water. Herein, we report the effects of loading of the different types of amphiphilic additives (non-ionic and ionic surfactants) on the fully hydrated Pn3m phase of α-Gal-OC10C6 lipid. Moreover, the effect of adding cholesterol, a membrane stiffening agent on the lipidic cubic system was also inspected. The influence of these additives and their concentrations on the ternary α-Gal-OC10C6/additive/water system has been investigated using small angle X-ray scattering at 25 °C. The comparison of these observations in relation to the phase behavior, structural properties, and interfacial curvature are discussed. In general, addition of increasing amounts of the non-ionic and ionic additives promote phase transitions towards less negatively curved phases than the Pn3m phase in the resultant ternary mixture. On the contrary, the cholesterol induces phase transformations towards the highly negatively curved phases. This study contributes to a better understanding into the effects of additives on the lyotropic cubic phase-forming lipid and its curvature tunability useful for designer delivery system.