STREAMING POTENTIAL MEASUREMENTS AS A TOOL TO STUDY PROTEIN ADSORPTION-KINETICS

A streaming potential method for in situ monitoring of protein adsorption from a laminarly flowing solution onto the walls of a flow cell is described. As a result of the adsorption of an electrically charged protein molecule, the ζ-potential of the adsorbing surface changes, which, in turn, gives rise to a proportional variation in the streaming potential between both ends of the flow cell. Assuming a linear relation between the ζ-potential, or for that matter, the streaming potential, and the adsorbed amount (which, in an independent study, has been verified for a number of proteins at various surfaces), the rate of protein adsorption can be derived. It is thus shown that in the initial stages the adsorption kinetics can be described by the Lévéque theory for transport by convective flow and diffusion simultaneously. The fraction of the protein molecules that become attached after reaching the surface decreases with decreasing electrostatic attraction between the protein and the sorbent. Unlike other techniques to study protein adsorption kinetics, the streaming potential method has the advantage that the protein molecules are not modified by the introduction of some extrinsic label that might affect the adsorption properties. © 1990.