Tuning Protein Uptake through Charge and Hydrophobicity in Peptide-Based Complex Coacervates

Protein encapsulation holds considerable promise for applications spanning the food, pharmaceuticals, biocatalysis, and personal care industries. Complex coacervation─an associative liquid-liquid phase separation (LLPS) process─has recently emerged as an effective strategy for achieving high protein loading while maintaining protein structure and function. In this work, we systematically investigate the influence of the coacervate-forming peptide charge density, charge patterning, and hydrophobicity on the partitioning of two model proteins: hen egg white lysozyme (HEWL) and bovine serum albumin (BSA). Using a rationally designed library of synthetic polypeptides, we demonstrate that protein uptake is highly sensitive to both the sequence features and hydrophobicity of the peptides, as well as the surface charge characteristics of the protein cargo. In particular, the localized charge patches on HEWL were sensitive to peptide charge density and patterning, while the hydrophobic character of BSA resulted in preferential partitioning into more hydrophobic coacervates. These findings highlight the critical role of spatial charge distribution and sequence composition in governing protein-coacervate interactions, offering new design principles for tailoring coacervate systems for bioencapsulation and related applications.