Separation Science Challenges and Opportunities in Designing and Understanding Improved Stationary Phases for Biopharmaceutical Purification

Prof. Giorgio Carta

Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia, USA

The efficiency of chromatographic purification of biopharmaceuticals at the industrial scale is highly limited by the large size of these biomolecules and by their slow kinetics of adsorption and desorption. As a result, improved stationary phases with higher binding capacity and faster kinetics are needed to cope with the ever-increasing scale and purity demands of biopharmaceutical production, especially for monoclonal antibodies. Ion exchangers containing grafted charged polymers have become available in recent years for preparative chromatography of proteins. These materials combine the desirable characteristics of a soft, hydrophilic polymer with those of a rigid support matrix allowing operation at high flow rates of the mobile phase. Compared to macroporous matrices without grafted polymers, these composite materials exhibit higher binding capacity and fast adsorption kinetics, making them ideal for capture from dilute protein solutions. But how do these materials achieve faster transport without comprising capacity? The combined use of macroscopic measurements, microscopic measurements using confocal laser scanning microscopy to track the movement of proteins within the chromatographic particles, and transport modeling provides mechanistic insight. We show that protein capacity is increased by multilayer binding while transport is enhanced by close-range biomolecular interactions within the charged polymers giving rise to a large diffusional driving force. We also address the large effects that subtle charge variants arising from post-translational modifications have on chromatography and transport in these materials. Mechanistic models and conditions under which these composite matrices show promise for various applications are illustrated and an outlook for the future is provided.