The adsorption of serum proteins on polymer microspheres is very important for their application in many fields．Various amounts of sulfonate groups were introduced to PMMA microspheres

and the adsorption behaviors of BSA on them was studied．The apparent rate constants of various microspheres increased with the increase amount of sulfonate groups on the surface of microspheres. Adsorption isotherm curves were fitted to the Langmuir-Freundlich model. With the increase of sulfonate groups on the surface of microspheres

cm values increased

however

K showed an opposite tendency to cm．It is indicated that the electrostatic interaction plays a dominant role in the adsorption process

and adsorption based on electrostatic interaction is higher than that due to hydrophobic interaction

but the adsorption due to electrostatic interaction has a lower rate than that of the latter.