Selective protein separation enabled by asymmetric three-component coacervates.

Selective protein separation via complex coacervation offers a sustainable alternative to conventional purification methods. Here, we investigate asymmetric coacervates formed by a polyelectrolyte and an oppositely charged multivalent ion as a platform for separating proteins from mixed solutions based on their isoelectric point (pI). Model systems include bovine serum albumin (BSA, pI ∼ 5.5) and hen egg white lysozyme (HEWL, pI ∼ 11). Encapsulation proceeds via ternary coacervate formation, where proteins act as effective species competing in the coacervation process. Phase separation and partitioning are governed by composition, pH, and ionic strength. Under physiological conditions, polystyrene sulfonate/tetraethylenepentamine selectively sequesters HEWL into the coacervate, leaving BSA in the supernatant, while poly(allylamine)/sodium tripolyphosphate reverses selectivity. These results demonstrate efficient protein separation from binary mixtures and provide mechanistic insight into asymmetric coacervation as a platform for selective purification and encapsulation.