Ultrastable Water-in-Oil High Internal Phase Emulsions Featuring Interfacial and Biphasic Network Stabilization

In this work, we present gel-in-gel
water-in-oil (W/O) high internal
phase emulsions (HIPEs) that feature high stability by structuring
both phases of the emulsion. Compared to significant advances made
in oil-in-water (O/W) HIPEs, W/O HIPEs are extremely unstable and
difficult to generate without introducing high concentrations of surfactants.
Another main challenge is the low viscosity of both water and oil
phases which promotes the instability of W/O HIPEs. Here, we demonstrate
ultrastable W/O HIPEs that feature biphasic structuring, in which
hydrogels are dispersed in oleogels, and self-forming, low-concentration
interfacial Pickering crystals provide added stability. These W/O
HIPEs exhibit high tolerance toward pH shock and destabilizing environments.
In addition, this novel ultrastable gel-in-gel W/O HIPE is sustainable
and made solely with natural ingredients without the addition of any
synthetic stabilizers. By applying phase structuring within the HIPEs
through the addition of various carrageenans and beeswax as structurants,
we can increase the emulsion’s stability and viscoelastic rheological
properties. The performance of these gel-in-gel W/O HIPEs holds promise
for a wide range of applications. As a proof of concept, we demonstrated
herein the application as a gelled delivery system that enables the
co-delivery of hydrophilic and hydrophobic materials at maximized
loads, demonstrating high resistance to gastrointestinal pHs and a
controlled-release profile.