Multicomponent adsorption of monoclonal antibodies on macroporous and polymer grafted cation exchangers

We compare the rates of adsorption of two monoclonal antibodies (mAbs) with different adsorption properties on the cation exchangers UNOsphere™ S and Nuvia™ S. The former contains large open pores while the latter is based on a backbone matrix similar to UNOsphere™ S but also contains grafted charged polymers. Both single component and two-component adsorption are considered. Adsorption capacity and rates are much higher for Nuvia™ S indicating that protein interactions with the charged grafted polymers facilitate both binding and diffusional transport. Intraparticle concentration profiles obtained by confocal microscopy show sharp fronts for UNOsphere™ S but diffuse profiles for Nuvia™ S. Transport is thus controlled by pore diffusion for UNOsphere™ S but is described by a single file diffusion (SFD) mechanism for Nuvia™ S. As a result, single and two-component adsorption occur at similar rates for UNOsphere™ S independent of the direction for transport. For Nuvia™ S, however, transport is very fast for single or two-component co-adsorption but very slow when counter diffusion of the two mAbs takes place within the particles. The transport models developed in this work allow a prediction of separation performance for overloaded conditions typical of process scale applications.