Preparation of pore-filled responsive membranes using dextran precipitation

A novel method for the preparation of a composite pore-filled membrane based on self-assembled hydrogels is described. Responsive pore-filled membranes based on mixtures of dextran (molecular weight 6000) and the glucose binding lectin Concanavalin A (ConA) were prepared. The transport properties of these membranes were characterised using a twin chamber diffusion cell with Cibacron blue as a tracer solute. As the ConA molecules introduce affinity cross-links into the gel structure by binding to terminal glucose moieties on the dextran chains the mesh size increased as the physical cross-link density of the hydrogel decreased with increasing competing glucose concentration. This increased the gel-phase diffusion coefficient for the tracer with results obtained for the effect of glucose on transport rates showing a linear increase up to a concentration of 40 mM. Further increases in d-glucose concentration lead to a subsequent decrease in transport rate which is attributed to the effects of gel swelling increasing the diffusion path length. Control experiments conducted with l-glucose, which does not bind to ConA, showed no increase in transport rate confirming a specific competition effect.