Direct and indirect thermal transitions from hexosomes to emulsified micro-emulsions in oil-loaded monoglyceride-based particles

Abstract

We identified the possible internally self-assembled phases that occur in oil-loaded monoglyceride-based nanoparticles that are dispersed in water. Temperature versus composition of the dispersed phase “ T– δ” phase diagrams were constructed at a constant dispersed phase content upon varying the oil/monoglyceride weight ratio at a wide range of temperatures (1–90 °C). We mainly focused on the determination of these phase diagrams by changing the oil type or the monoglyceride purity. They were built when investigating the internal structure of the particles by means of small angle X-ray scattering (SAXS). We show that some internally self-assembled emulsified particles may contain a discontinuous cubic phase ( Fd3m symmetry), depending on the oil content. However, the extension of this phase in the diagram strongly depends on the oil. This emulsified liquid crystalline phase is inserted between the inverse hexagonal H 2 phase and the inverse micellar solution L 2 phase, as was previously found in bulk. Moreover, we managed to find the existence of an indirect thermal transformation from hexosomes to emulsified micro-emulsions through micellar cubosomes (emulsified reversed discontinuous micellar cubic phase) within a narrow range of an oil/monoglycerides ratio. This transition via temperature has not been published to our knowledge in these dispersed systems.