The Ouzo effect: A tool to elaborate high-payload nanocapsules

Abstract

We investigate the encapsulation in hybridosomes®, a type of capsules unique regarding their structure and method of elaboration. Hybridosomes® are made of a single shell of inorganic nanoparticles (~5 nm) crosslinked with a polymer and are easily obtained via spontaneous emulsification in a ternary mixture THF/water/butylated hydroxytoluene (BHT). Our main finding is that an exceptionally high concentration of a hydrophobic model dye can be loaded in the hybridosomes®, up to 0.35 mol.L−1 or equivalently 170 g.L−1 or 450,000 molecules/capsule. The detailed investigation of the encapsulation mechanism shows that the dye concentrates in the droplets during the emulsification step simultaneously with capsule formation. Then it precipitates inside the capsules during the course of solvent evaporation. In vitro fluorescence measurements show that the nano-precipitated cargo can be transferred from the core of the hybridosomes® to the membrane of liposomes. In vivo studies suggest that the dye diffuses through the body during several days. The released dye tends to accumulate in body-fat, while the inorganic nanoparticles remain trapped into the liver and the spleen macrophages.