A C-13 NMR study of aqueous dispersions of reversed lipid phases

Monoolein (GMO) forms a bicontinuous cubic phase that can coexist in equili brium with a water phase, and this phase can be dispersed into colloidal pa rticles. Poloxamer is an efficient stabilizer for dispersions of this phase . By adding a small amount of triolein to GMO, a reversed hexagonal phase i s formed :It room temperature. This phase can be dispersed into submicron p articles in water in the same way. The inner molecular arrangement of these dispersions was investigated by C-13 NMR relaxation. The C-13 NMR relaxati on rates of the various GMO carbon atoms obtained from the dispersed partic les compared to those obtained from the nondispersed phases indicate that t he lipid organization and dynamic properties of the original nondispersed p hases are retained. It is also demonstrated that the cubic phase is transfo rmed into the reversed hexagonal phase, within six months, due to hydrolysi s of GMO. A remarkable observation, is that no significant hydrolysis occur s during this time in the corresponding dispersed samples. This indicates t hat solubilization of a few wt % of Poloxamer into the GMO bilayer provides protection against degradation.