3M Polisher ST anion exchange purifier

The 3M Polisher ST is a fully encapsulated single-use anion exchange (AEX) product intended to reduce host cell protein (HCP) impurities, viruses and other negatively charged contaminants in flow-through polishing chromatography of biopharmaceutical process streams. It is a synthetic, hybrid purifier containing two complementary AEX-functional media: a quaternary ammonium (‘Q’) functional nonwoven and a guanidinium (Gu) functional membrane.

Ion exchange chromatography is a commonly used downstream polishing purification technique in the production of mAbs and many other therapeutic proteins. The limitation with traditional anion exchange chromatography is that the binding capacity is diffusion-limited and the interaction strength of the ligand depends on operating conditions like pH and conductivity.

The 3M product, with its nonwoven and membrane skeletons, provides mechanical strength and durability, while the grafted hydrogel functionality creates a large three-dimensional surface area that contains a high density of functional groups with interconnected pores allowing for convective flow channels that are able to achieve high flow rates. The high density of binding sites, together with a macroporous structure, enables high binding capacity for not only HCP, but also large molecules, such as viruses and DNA. The high density of binding sites and low residence time also results in high mAb recovery (>95%).

The high ligand density on the advanced anion exchange membrane provides robust impurity removal and viral clearance. It also provides a 50 to 100x higher mAb load capacity than chromatography resin beads, the company says, which allows further reduction of the media volume requirement. The impurity clearance performance (HCP≤1000 ppm, ≤100 ppb DNA, and viral clearance) is independent of the load up to 10 kg/m², enabling downsizing of the unit operation.

Other benefits include: operation in robust process conditions (pH 5 to 9 and conductivity 3 to 20 mS/cm); HCP reduction of >60% in phosphate buffer, >22% in citrate buffer; virus reduction >4-log; DNA clearance down to LOD levels (~0.05 ppb DNA); ease of use due to elimination of column packing, unpacking, cleaning and storage; and downstream process intensification through a combination of high flow rates with high binding.