Adsorption of bovine serum albumin onto styrene/2-hydroxyethyl methacrylate copolymer latex

Abstract

The adsorption of bovine serum albumin (BSA) onto styrene (S)/2-hydroxyethyl methacrylate (HEMA) copolymer (PS/PHEMA) latex was studied. Polystyrene (PS) latex was used as a reference sample. All these latices were prepared without emulsifier and were highly monodisperse. The measurement results of surface charge density and ζ potential for these latices suggested that hydrous poly-HEMA layer existed on the surface of PS/PHEMA latex particles. The plateau values of the adsorption isotherms implied that BSA molecules adsorbed onto PS and PS/PHEMA latices in a side-on form at least near the isoelectric point (iep) of this protein. The adsorbability of BSA onto HEMA-copolymerized latex showed a similar tendency to that onto PS latex in the acidic pH region lower than the iep. However, in the alkaline pH region especially at a higher ionic strength, BSA adsorption onto HEMA-copolymerized latex was quite different from that onto PS latex. Namely, the amount adsorbed onto HEMA-copolymerized latex was hardly discernible at this pH region regardless of ionic strength.