Purification of monoclonal antibodies in a stirred cell with polyethyleneimine‐modified polyethersulfone ultrafiltration membrane

BACKGROUND Charged ultrafiltration membranes combined with optimal operating conditions can be used to enable monoclonal antibody purification. Positively charged ligands bound to the membrane surface can significantly contribute to the adsorption of negatively charged proteins and enhance the purification process. RESULTS In this work, commercially available 500 kDa polyethersulfone ultrafiltration membranes were modified by sulfonation, followed by deposition of polyethyleneimine (PEI) and crosslinking with butanedioldiglycidylether. Polymer molecules of 2 and 10 kDa were used to evaluate how polymer size influences the fractionation of a harvested Chinese hamster ovary cell culture fluid containing a monoclonal antibody by ultrafiltration at different operational pH values. The precursor and modified membranes were analyzed by X-ray photoelectron spectroscopy, which confirmed the successful modification of membranes. Nitrogen analysis showed the presence of amine groups, clearly confirming immobilization of PEI onto the membrane surface. When 10 kDa PEI is chosen for membrane modification, the intensity of this signal increases, as predicted for a higher-molecular-weight polymer. Ultrafiltration performance indicators (fluxes, transmissions, yields) were determined and compared for the modified and precursor membranes, with the PEI-derived membranes showing ability for pH modulation of selectivity. CONCLUSION High purities were consistently observed at pH 9 owing to a simultaneous decrease in the transmission of soluble protein and increase in both IgG transmission and adsorptive capacity of the membranes. A single-step process at pH 9 renders a permeate with an antibody purity of 96%, using a non-crosslinked membrane modified with 10 kDa PEI. (c) 2019 Society of Chemical Industry