pH-responsive double hydrophilic protein-polymer hybrids and their self-assembly in aqueous solution

Double hydrophilic protein-polymer hybrids were successfully prepared by "grafting-to" method. Sodium polyacrylate (PANa) with an activated end group was prepared using acrylic acid as initial monomer by atom transfer radical polymerization (ATRP) in the water/DMF mixture at pH 7.8. Then, the activated end group of PANa directly covalently binds to the primary amino groups of the lysine of bovine serum albumin (BSA) in phosphate buffer solution (PBS) at pH 7.4. BSA-PANa hybrids were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-associated laser desorption/ionization time-of-flight mass spectra (MALDI-ToF MS). UV-vis spectrometer, transmission electron microscopy (TEM), and dynamic light scatter (DLS) were used to study their self-assembly in PBS at different pH. The resulting BSA-PANa hybrids were pH-responsive. They were found to form spherical structures with narrow distribution in PBS at pH 7.4. In PBS at pH 2.5, fewer spherical particles with broad distribution were visible. Meanwhile, spherical particles had a very thin wall with thickness of 10 nm.

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