Hierarchical Plant Protein Microcapsules for Hydrophilic and Hydrophobic Cargo Molecules

Abstract: Microscale hydrogels comprised of macromolecular networks have increasingly been used for applications involving cell encapsulation, tissue engineering and for the storage and release of active cargo molecules. However, the majority of such microgels are formed from nonbiodegradable synthetic polymers, involving harmful solvents, or using animal proteins, such as silk and gelatin, which can have a negative environmental impact and lack sustainability. Furthermore, most encapsulation techniques involve either protecting hydrophobic or hydrophilic cargo, but rarely both. In order to address these issues, we employed droplet-microfluidics to develop novel, plant protein microcapsules capable of containing both hydrophilic and hydrophobic cargo molecules. The microcapsule structure and cargo release rates were controlled by balancing osmotic pressures between the outer and inner phases of the capsules. Moreover, the digestibility of the microcapsules was comparable with that of pure pea protein, thereby enabling the use of these microcapsules for food and beverage applications. In addition, digestive enzymes can trigger the release of the encapsulated active ingredients, and hence, these microcapsules are well suited for the controlled delivery of active nutraceutical or pharmaceutical ingredients. Finally, we investigated the biodegradability of the microcapsules. It was determined that the plant protein microcapsules exhibited 98.0% biodegradability (as compared with cellulose), thereby fulfilling the biodegradability standards stipulated by the International Organization for Standardization (ISO 14851) for microplastics in freshwater conditions (90%). Hence, the plant protein microcapsules can have numerous applications in the food, nutraceutical, pharmaceutical, cosmetic, personal care, and agriculture industries.