Biomacromolecules in Ternary Complex Coacervates

Vaccines and other therapeutic cargo are made, transported, and stored along a “cold chain,” a system designed to maintain the refrigeration of these fragile cargos. To combat this, methods for decreasing the reliance of these cargos on the cold chain have garnered attention, with many efforts focusing on encapsulation strategies. Our work focuses on complex coacervation as an all-aqueous encapsulation strategy. Complex coacervation is a liquid-liquid phase separation phenomenon dominated by electrostatic interactions and entropy. We investigated the use of a two-polymer coacervate system for protein encapsulation to facilitate the incorporation of weakly-charged protein cargo and explored the incorporation of three model proteins as a function of solution conditions, polymer properties, and distribution of charges on the proteins. We determined that the net charge and distribution of charges on both the protein and polymers dominated protein incorporation, and confirmed this by comparing the incorporation of two variants of caspase-6 that differ in a critical charged patch. Our results have shown the encapsulation of caspase-6 almost doubled in the level of partitioning when displaying a charge patch.