Ultrastable High Internal Phase Pickering Emulsions: Forming Mechanism, Processability, and Application in 3D Printing.

High internal phase Pickering emulsions (HIPPEs) are versatile platforms for various applications owing to their low-density, solid-like structure, and large specific surface area. Here, naturally occurring polysaccharide-protein hybrid nanoparticles (PPH NPs) were used to stabilize HIPPEs with an internal phase fraction of 80% at a PPH NP concentration of 1.5%. The obtained HIPPEs displayed a gel-like behavior with excellent stability against centrifugation (10000g, 10 min), temperature (4-121 °C), pH (1.0-11.0), and ionic strength (0-500 mM). Confocal laser scanning microscope and cryo-scanning electron microscopy results showed that PPH NPs contributed to the stability of HIPPEs by effectively adsorbing and anchoring on the surface of the emulsion droplets layer by layer to form a dense 3D network barrier to inhibit droplet coalescence. The rheological analysis showed that the HIPPEs possessed a higher viscosity and lower frequency dependence with increasing PPH NP concentration, suggesting the potential application of such HIPPEs in three-dimensional (3D) printing, which was subsequently confirmed by a 3D printing experiment. This work provides highly stable and processable HIPPEs, which can be developed as facile and reusable materials for numerous applications. They can also be directly used for future food manufacturing, drug and nutrient delivery, and tissue reconstruction.

Panax Notoginseng polysaccharide stabilized gel-like Pickering emulsions: Stability and mechanism.

In this work, the polysaccharide from Panax Notoginseng (SPNP), a traditional herb in China, was used as an outstanding Pickering stabilizer to fabricate Pickering emulsions. The SPNP was characterized to be a porous network structure with a rough surface surrounded by some nanoparticles. Rheological measurement of the obtained Pickering emulsions demonstrated the formation of emulsion gels. Moreover, the emulsions exhibited excellent storage (14 days), pH (1.0-11.0), ionic strength (0-500 mM), and temperature (4-50 °C) stabilities. In addition, the Pickering emulsions showed a freeze-thaw stability, which is beneficial in food, cosmetic or biomedical applications when they may require freezing for storage and melting before use. Confocal laser scanning microscope (CLSM) and cryo-scanning electron microscopy (cryo-SEM) results showed that SPNPs effectively adsorbed at the oil-water interface by forming a compact three-dimensional (3D) network structure and multilayer anchoring on the surface of the emulsion droplets, thus inhibiting the droplet coalescence and flocculation. This study provides a kind of Pickering emulsions applicable in food, biomedical and cosmetic industries.