Effects of Control Factors on Protein–Polyelectrolyte Complex Coacervation

Abstract

Protein−polyelectrolyte complex coacervation is of particular interest for mimicking intracellular phase separation and organization. Yet, the challenge arises from regulating the coacervation due to the globular structure and anisotropic distributed charges of protein. Herein, we fully investigate the different control factors and reveal their effects on proteinpolyelectrolyte coacervation. We prepared mixtures of BSA (bovine serum albumin) with different cationic polymers, which include linear and branched polyelectrolytes covering different spacer and charge groups, chain lengths, and polymer structures. With BSA-PDMAEMA [poly(N,N-dimethylaminomethyl methacrylate)] as the main investigated pair, we find that the moderate pH and ionic strength are essential for the adequate electrostatic interaction and formation of coacervate droplets. For most BSA−polymer mixtures, excess polyelectrolytes are required to achieve the full complexation, as evidenced by the deviated optimal charge mixing ratios from the charge stoichiometry. Polymers with longer chains or primary amine groups and a branched structure endow a strong electrostatic interaction with BSA and cause a bigger charge ratio deviation associated with the formation of solid-like coacervate complexes. Nevertheless, both the liquid-and solid-like coacervates hardly interrupt the BSA structure and activity, indicating the safe encapsulation of proteins by the coacervation with polyelectrolytes. Our study validates the crucial control of the diverse factors in regulating protein−polyelectrolyte coacervation, and the revealed principles shall be instructive for establishing other protein-based coacervations and boosting their potential applications.

Nanodroplets Engineered with Folate Carbon Dots for Enhanced Cancer Cell Uptake toward Theranostic Application

“…Despite these advancements, challenges such as low drug loading, i.e., less than 70%, short retention time, and drug leakage during administration persist . In contrast, droplets also known as coacervates offer a unique solution with their membrane-free structure and the ability to load various DNA, proteins, and enzymes. − These droplets exhibit sizes ranging from 100 nm to 10 μm and are formed through electrostatic interactions between oppositely charged polyelectrolytes during the spontaneous liquid–liquid phase separation process . The size of droplets can be regulated by adjusting the polyelectrolyte ratio, solution pH, ionic strength, and reaction time .…”