Sequential adsorption of F(ab′) 2 and BSA on negatively and positively charged polystyrene latexes

The aim of the present work is to study the sequential adsorption of F(ab′) 2 and bovine serum albumin (BSA) molecules adsorbed onto positively and negatively charged polystyrene latexes. Cationic and anionic latexes were prepared by emulsifier‐free emulsion polymerization. Adsorptions of F(ab′) 2 on both latexes at a low ionic strength and different pHs were performed. The cationic latex showed a higher adsorption of F (ab′) 2 molecules over a range of pH, which could be due to the formation of multilayers. Sequential adsorption of anti‐CRP F(ab′) 2 and monomeric BSA were performed at two different pre‐adsorbed F(ab′) 2 amounts on both types of latex. Displacement of F(ab′) 2 occurred only when the preadsorbed amounts were larger than a certain critical value, which depends on the adsorption pH. A greater displacement of larger preadsorbed amounts might be the result of a weaker contact between the protein molecules and the polystyrene surface. The displacement of F(ab′) 2 previously adsorbed onto both latexes occurred due to pH changes, an increase of ionic strength and the presence of BSA molecules. The effect caused by these three factors was studied independently. The main factors in the desorption of F(ab′) 2 on the anionic latex are the changes in pH and ionic strength, whereas on the cationic latex the desorption is mainly caused by the increase of the ionic strength and the presence of BSA. The colloidal stability of the immunotatex was improved by BSA adsorption, especially on cationic latex. © 1995 John Wiley & Sons, Inc.