Adsorption of BSA onto sulfonated microspheres

The adsorption of bovine serum albumin (BSA) onto modified PMMA microspheres was studied. The sulfonate groups on the surface of microspheres play an important role in this system. From microsphere 1 to 4, with the increase in amount of sulfonate groups on the surface of microspheres, the apparent constants increased from 2.28 to 3.18 × 10−2 min−1. The adsorption isotherms were fitted to the Langmuir-Freundlich isotherm. With the increase of sulfonate groups on the surface of microspheres, Cm values increased and K values decreased. Close to the isoelectric point of BSA, the adsorption amount exhibits a maximum. A higher or lower pH results in the significant decrease of the adsorption amount. And with the increase of ionic strength, the adsorption of BSA onto microspheres decreased. This may be responsible for the binding of Cl− and BSA, which resulted in a degree of change in the conformation and local charge of BSA macromolecules.