Scale-Down Analysis of Fouling in Cell Retention Devices for the Continuous Production of Monoclonal Antibodies

The use of perfusion bioreactor systems is increasing in biomanufacturing due to their potential for productivity gains, increased facility utilization, and process intensification. Systematic studies on cell retention devices are limited even if these devices are often described as process-limiting during perfusion. This work aims to address this gap by establishing a scale-down model for perfusion that enables the specific investigation of fouling, whether due to submicron particles or soluble foulants, in a cell retention device. A methodology was developed to simulate aspects of perfusion culture and investigate the impact of fouling components from the cell culture. To mimic large-scale cell culture, the feed to a filter membrane was varied using quasi-perfusion in flasks over several days. The effect of upstream changes on filter capacity was evaluated using ultra scale-down normal flow filtration, including studies of cell culture and cell-free supernatant harvest for pore size selection. By replicating the impact of shear from industrial pumps during fluid transport (i.e., from bioreactor to the retention device), the kompAs ultra scale-down shear device demonstrated a significant reduction in filter capacity due to shear exposure. Lastly, a very small-scale TFF system (16 cm²) was used to simulate the continuous filtration during perfusion and to evaluate the filter operation using cell-free feeds to investigate the impact of soluble foulants. The novel application of these ultra scale-down tools revealed the main fouling mechanism (pore constriction) and the major soluble foulant in this study (DNA rather than the product or host cell proteins).