A new multimodal membrane adsorber for monoclonal antibody purifications

This contribution describes research on the use of a newly developed multimodal membrane (MMM) adsorber that can be used as a chromatographic stationary phase in bioseparation processes. Compared with commercial cationic multimodal adsorbers, this MMM has superior static binding capacity (SBC=180mg IgG/ml), dynamic binding capacity (DBC_10%=60mg IgG/ml), and load productivity (>10mg/ml/min). Furthermore, the incorporation of functional groups that provide orthogonal modes of interactions increases the range of ionic strength for operation of the MMM relative to conventional ion-exchange and hydrophobic interaction chromatography media. The effects of different salt types (kosmotropic, neutral, chaotropic salts) and ionic strength on IgG binding were investigated. To further understand the protein adsorption on the MMM, a thermodynamic model was employed to describe IgG adsorption isotherms on the MMM by providing a unique set of physically meaningful parameters for each salt type. The model was also a precise predictor of the adsorption isotherms under non-test conditions. A breakthrough analysis was used to determine dynamic binding capacities. The MMM maintained 70% DBC as ionic strength increased from 0 to 300mM NaCl. Finally, a range of flow rates was used to study the effect of volumetric throughput on DBC. Because DBC was insensitive to flow rate, process productivity increased with flow rate nearly linearly up to high linear velocity (535cm/h). A kinetic study indicated that the rate limiting step of IgG binding on the MMM was the adsorption rate, not the convective mass transport of protein molecules to binding sites.