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 positi vely and negatively charged polystyrene latexes. Cationic and anionic latexes were prepared by emulsifier-free emulsion polymerization. Adso rptions of F(ab')(2) on both latexes at a low ionic strength and diffe rent 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 l arger preadsorbed amounts might be the result of a weaker contact betw een the protein molecules and the polystyrene surface. The displacemen t of F(ab')(2) previously adsorbed onto both latexes occurred due to p H changes, an increase of ionic strength and the presence of BSA molec ules. The effect caused by these three factors was studied independent ly. The main factors in the desorption of F(ab')(2) on the anionic lat ex are the changes in pH and ionic strength, whereas on the cationic l atex the desorption is mainly caused by the increase of the ionic stre ngth and the presence of BSA. The colloidal stability of the immunolat ex was improved by BSA adsorption, especially on cationic latex. (C) 1 995 John Wiley & Sons, Inc.