Effect of hydrophobic/hydrophilic characteristics of magnetic microspheres on the immobilization of BSA

Core-shell magnetic poly(styrene-acrylamide-acrylic acid) microspheres with carboxyl groups were successfully synthesized via dispersion copolymerization in the presence of nano-particle of Fe3O4. The microspheres were characterized by FTIR spectra. They were used as carrier to immobilize bovine serum albumin (BSA). To investigate the effect of the microsphere surface properties on the immobilization of BSA, a series of microspheres with different hydrophobic/hydrophilic surface characteristics were prepared by adjusting molar percentages of monomers. The results showed that microspheres with different hydrophobicities/hydrophilicities had different immobilized ratios of BSA. In comparison with microspheres having hydrophilic characteristics those with hydrophobic characteristics had a much higher immobilized ratio. The possible reasons for these observations are discussed. In addition, ester activation and coupling times were optimized with respect to immobilized ratio.