SELECTIVE AUGMENTATION OF MACROMOLECULAR TRANSPORT IN GELS BY ELECTRODIFFUSION AND ELECTROKINETICS

Application of an electric field across polyelectrolyte hydrogel membranes can promote membrane charging and swelling, drive electro-osmotic convection, and produce electrophoresis of charged solutes within the membrane. The selective changes in transmembrane solute flux which result suggest a new separation technique based on the size and charge of the solutes. Experiments demonstrte the pH dependence of diffusive, electro-osmotic and electrophoretic transport of fluorescently labeled proteins and neutral solutes across polymethacrylic acid (PMAA) and polyacrylamide membranes. In the presence of a pH gradient across ionizable PMAA, electrically induced changes in swelling and permeability are attributed to an electrodiffusion mechanism; in addition to altering membrane swelling and permeability, intramembrane pH changes associated with electrodiffusion can affect solute flux by modulating both electrokinetic transport and electrostatic partitioning of charged proteins within the membrane. A combination of these transport mechanisms can enable large, electrically controlled changes in the separation of proteins, as demonstrated by a 21-fold change in the relative flux of labeled BSA and RNase across a PMAA membrane. © 1990.