Clarification of a monoclonal antibody with cationic polyelectrolytes: Analysis of influencing parameters

Precipitation with polyelectrolytes is a promising alternative to conventional methods for purification of monoclonal antibodies (mAb). This study focuses on clarification of a monoclonal antibody by precipitation of the model impurity bovine serum albumin (BSA) with cationic polyelectrolytes. Different types of cationic polyelectrolytes with different functional amine groups and molecular weights are screened for their capability to precipitate BSA in mixture with mAb. Due to the high BSA depletion and mAb recovery achieved, two cationic polyelectrolytes, polyethyleneimine (PEI) and polyallylamine (PAA) with a molecular weight of 65 kDa were selected as most suitable precipitation agents. Additionally, influences of different parameters (polyelectrolyte, BSA and NaCl concentration and pH value) were analyzed by the use of design of experiments (DoE). Herewith, a fast identification of influencing factors and factor interaction was achieved. With DoE, two regression models for the analysis of BSA depletion in dependence of influencing factors were established. This enabled the analysis of the robustness of precipitation as initial clarification step of downstream process of mAb.