Formation and characterization of multiple W/W/W emulsions

Abstract

This project was focused in the preparation, stabilization and characterization of multiple water-in-water-in-water W/W/W emulsions. These emulsions are very interesting, because they constitute oil-free dispersions, and very few studies can be found in scientific literature. The studied aqueous two-phase system is composed of gelatin from bovine skin and maltodextrin. These components have been chosen due to their biocompatibility and low cost. The absence of surfactants and nanoparticles makes multiple W/W/W emulsions very biocompatible to be used for pharmaceuticals applications. In previous work, phase behaviour in maltodextrin-gelatin mixtures have been studied. These colloidal systems can be prepared by mixing two immiscible water-soluble polymers in aqueous solution, such as a polysaccharide and a protein. These systems show complex phase behaviours, which can be controlled by changing pH and ionic strength. In the present work, the formation of multiple water-based emulsions by two different methods has been studied. The two-step method consists in a first preparation of the primary emulsion followed by a dropwise addition to an external phase. The other method is based on inducing a secondary phase separation in simple emulsions droplets by decreasing the temperature. The emulsions have been characterized using fluorescence microscopy and differential interference contrast microscopy. Moreover, parameters influencing the structure and preparation have been optimized, the optimal conditions are shown in Figure. Stability of dispersions has been improved by gelifiying the gelatin phase, either by cooling down or crosslinking with genipin