Biocompatible oil-in-water-in-oil double emulsion stabilized synergistically by phytosterol/chitosan complex particle and gelatin

Herein we reported highly biocompatible and stable oil-in-water-in-oil (o/w/o) Pickering double emulsions (PDEs) using a one-step emulsification procedure. Natural phytosterol (PS) particles and chitosan (CS) self-assembled into PS/CS complex paritlces to serve as particulate stabilizers while gelatin was used as viscosity modifier for aqueous phase. By varying the viscosity of aqueous phase, water/oil volume ratio, and homogenization time, the formation and stabilization mechanism of o/w/o PDEs were explored. The viscosity of aqueous phase and occurrence of phase inversion are essential for the formation of PDEs. Additionally, the adsoprtion of PS/CS complex particles on the oil/water interface and high viscosity of aqueous phase both aid in the stabilization of PDEs. Furthermore, the o/w/o PDEs showed good storage stability at 4 °C and 25 °C (at least 2 months), with essentially little change in emulsion structure. And a variety of oils can be used to prepare the PDEs. What's more, the o/w/o PDEs can co-encapsulate hydrophilic and hydrophobic bioactive compounds, shielding them against UV exposure and long-term storage. In summary, these findings will not only aid in the development of biocompatible o/w/o PDEs, but also provide a guidance for co-encapsulating and protecting bioactive compounds that are both hydrophilic and hydrophobic.