Star Polyelectrolytes with Mixed Arms of PDMAEMA and POEGMA: Self‐Assembly and Coassembly with Insulin

Abstract

AbstractStar copolymers with mixed polyelectrolyte/hydrophilic arms of poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) and poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) have been synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization and the arm‐first method. The star polyelectrolytes self‐assemble in aqueous media in nanostructures of hydrodynamic radius in the order of 50 nm. The quaternized star‐QPDMAEMAx‐POEGMAy aggregates appear to have a higher surface charge and a looser morphology in comparison to the annealed (weakly charged) star‐PDMAEMAx‐POEGMAy aggregates. The cationic mikto‐arm stars coassemble into complexes with insulin (INS) at neutral pH. In the case of the annealed stars INS appears to bind homogeneously to the fractal‐like aggregates. However, in the quenched (strongly charged) stars the protein rather attaches to the periphery of the compact aggregates. Interestingly, the size and mass of the star/INS complexes pass through a maximum as a function of the salt content for high INS contents. This is attributed to the anisotropic charge distribution of INS at pH 7, an effect that is reported only for linear and not for star polyelectrolytes. This work motivates the use of the star‐PDMAEMAx‐POEGMAy polyelectrolytes for the immobilization and delivery of protein drugs.