Poly[(vinyl benzyl trimethylammonium chloride)]-based nanoparticulate copolymer structures encapsulating insulin

Abstract

We report on the synthesis and preparation of four double hydrophilic polyelectrolytes and their complexation with insulin (INS). Specifically, two cationic-neutral poly[oligo(ethylene glycol) methacrylate]-b-poly[(vinyl benzyl trimethylammonium chloride)] (POEGMA-b-PVBTMAC) and two poly[oligo(ethylene glycol) methacrylate-co-vinyl benzyl trimethylammonium chloride] (P(OEGMA-co-VBTMAC)) copolymers are successfully synthesized by reversible-addition fragmentation chain transfer (RAFT) polymerization with different compositions. Based on light scattering techniques (DLS, ELS), the POEGMA81-b-PVBTMAC19, POEGMA46-b-PVBTMAC54 P(OEGMA90-co-VBTMAC10), P(OEGMA75-co-VBTMAC25) (subscripts denote wt.% composition of the components) copolymers are present as single chains and aggregates in aqueous media. A significant aggregation tendency of bare copolymers into well-defined spherical-shape particles is also noticed in cryogenic transmission electron microscopy measurements (Cryo-TEM) measurements. The synthesized copolymers were utilized as nanocarriers for insulin (INS) encapsulation. Nanocarriers were formed via electrostatic co-assembly, and the effects of copolymer structure on the properties of the formed hybrid copolymer-INS nanostructures are studied. Physicochemical results on the copolymer/INS complexes corroborated the efficient complexation of INS with copolymers. The determined characteristics and the morphology of the copolymer/INS complexes were found to depend on (−)INS/(+)polymer charge ratio. The copolymer/INS complexes retain the initial spherical shape of neat copolymer aggregates after the electrostatic complexation with INS, according to Cryo-TEM measurements, also uncovering the presence of aggregates and threadlike structures. FBS interactions between bare copolymers and copolymer/INS complexes manifested a good stability of the hybrid copolymer/INS assemblies into a simulated biological environment. Moreover, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy shows physical interactions between INS and the respective polyelectrolytes. Fluorescence spectroscopy (FS) measurements indicated no significant changes on the conformation of complexed INS.