ADSORPTION OF MONOCLONAL IGGS AND THEIR F(AB')(2) FRAGMENTS ONTO POLYMERIC SURFACES

The present study deals with the adsorption of two monoclonal immune gamma globulins (IgGs) and their corresponding F(ab')(2) fragments onto three polymer latices. Two of these latices are hydrophobic, one being positively and the other negatively charged; the third is a negatively charged hydrophilic latex. Electrostatic and hydrophobic interactions were systematically studied by performing adsorption and electrophoresis experiments as a function of pH and ionic strength, and by using two IgCs which differ in isoelectric point. The affinity of the proteins for the hydrophobic latices was barely influenced by electrostatic interactions. However, at saturation level the adsorbed amounts were dependent on the overall electrostatic interaction, resulting in a maximum adsorbed amount when the protein charge is partly compensated by the sorbent surface charge. For the hydrophilic latex, there was no adsorption when the proteins were electrostatically repelled by the sorbent surface. The trends in the adsorption of IgG and the corresponding F(ab')(2) fragments were similar, although there was some evidence that hydrophobic interactions and/or conformational changes were less important for F(ab')(2) adsorption. At hydrophobic surfaces the protein molecules adsorbed mainly in an end-on orientation, whereas for a negatively charged hydrophilic latex and high cationic charge densities on the protein, the adsorbed amounts correlated with a close-packed monolayer of side-on oriented proteins.