posted on 2023-11-13, 11:40authored byJin Zhou, Yuting Wan, Martien A. Cohen Stuart, Mingwei Wang, Junyou Wang
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 protein-polyelectrolyte 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.