Protein Encapsulation Using Complex Coacervates: What Nature Has to Teach Us

Protein encapsulation is a growing area of interest, particularly in the fields of food science and medicine. The sequestration of protein cargoes is achieved using a variety of methods, each with benefits and drawbacks. One of the most significant challenges associated with protein encapsulation is achieving high loading while maintaining protein viability. This difficulty is exacerbated because many encapsulant systems require the use of organic solvents. By contrast, nature has optimized strategies to compartmentalize and protect proteins inside the cell-a purely aqueous environment. Although the mechanisms whereby aspects of the cytosol is able to stabilize proteins are unknown, the crowded nature of many newly discovered, liquid phase separated "membraneless organelles" that achieve protein compartmentalization suggests that the material environment surrounding the protein may be critical in determining stability. Here, encapsulation strategies based on liquid-liquid phase separation, and complex coacervation in particular, which has many of the key features of the cytoplasm as a material, are reviewed. The literature on protein encapsulation via coacervation is also reviewed and the parameters relevant to creating protein-containing coacervate formulations are discussed. Additionally, potential opportunities associated with the creation of tailored materials to better facilitate protein encapsulation and stabilization are highlighted.