Self-assembly of poly(ethylene glycol-b-phenyl oxazoline) diblock copolymers in aqueous media and their interactions with proteins

Amphiphilic block copolymers composed of poly(ethylene glycol) (PEG) and poly(2-phenyl-2-oxazoline) (PPhOx) with different molecular weights and compositions are synthesized. Their molecular characteristics are determined by size exclusion chromatography (SEC), proton nuclear magnetic resonance (1H NMR), and Fourier transform infrared spectroscopy (FTIR). In aqueous solutions, the size of the formed aggregates is much higher than the one expected from single core-shell micelles and point to larger spherical aggregates as observed by light scattering. The aggregation state is found temperature-sensitive. The internal environment of these aggregates is considerably polar as evidenced by pyrene fluorescence measurements. The interactions of the synthesized diblock copolymers with fetal bovine serum (FBS) proteins are investigated, and further aggregation of the initial structures is observed in the presence of serum proteins. The ability of the PEG-b-PPhOx aggregates to associate with proteins is tested for the case of bovine serum albumin (BSA) where it is found that indeed accumulation of BSA globules occur because of hydrophobic interactions between the protein and the hydrophobic domains of the polymeric aggregates.