Investigations on protein adsorption to agarose-dextran composite media

A new stationary phase for protein purification was investigated with regard to its performance during capture of selected model proteins. The commercially available matrix consists of a porous agarose backbone, to which dextran is covalently attached. The dextran carries ion-exchange ligands, thus providing a binding space of high ligand density. Breakthrough of various proteins during frontal application to packed beds was measured and the experiments were analyzed in terms of equilibrium and breakthrough capacity. A significant increase of static capacity, as compared with conventional porous matrices, was found. Good dynamic properties allowed utilization of a high percentage of the equilibrium capacity at 10% breakthrough. For all proteins, a decreasing ratio of breakthrough to equilibrium capacity was detected with increasing feed concentration. This observation suggested a significant contribution of solid diffusion to the transport of proteins into the adsorbent particles. The specific architecture of the stationary phase, where the agarose base structure is derivatized with ion-exchange ligand-bearing dextran, may lead to this behavior.