Shear contributions to cell culture performance and product recovery in ATF and TFF perfusion systems

Abstract

Achievement of a robust and scalable cell retention device remains a challenge in perfusion systems. Of the two filtration systems commonly used, tangential flow filtration (TFF) systems often have an inferior product sieving profile compared to alternating tangential flow filtration (ATF) systems, which is typically attributed to the ATF's unique alternating flow. Here, we demonstrate that observed performance differences between the two systems are a function of cell lysis and not the alternating flow as previously thought. The peristaltic pump used in typical TFF perfusion systems is shown to be the single major contributor to shear stress and cell lysis. Replacing the peristaltic pump with a low shear centrifugal pump brought cell growth, cell lysis, particle concentration, and product sieving in a TFF perfusion system to levels comparable with that of an ATF. These results provide a correlation where poor product sieving can be partially explained by high shear in cell retention systems and demonstrate that low shear TFF systems are a feasible alternative to ATF systems.

Larger Pore Size Hollow Fiber Membranes as a Solution to the Product Retention Issue in Filtration‐Based Perfusion Bioreactors

“…We have shown that 20–200 nm particles are associated with product retention on a 0.2 μm membrane . We hypothesize that rather than using a 0.2 μm filter, a larger pore filter would allow the 20–200 nm particles to pass through the membrane, and therefore reduce the amount of product retention.…”

Computational fluid dynamic modeling of alternating tangential flow filtration for perfusion cell culture

“…Previously, ATF has been modeled using a series of empirically derived equations where important parameters such as local velocity, pressure drop, and permeate flux are lumped into single average values (Kelly et al, ). The CFD approach presented in this study provided the basis for improved understanding of the impact of operating conditions on factors such as product sieving (Wang et al, ) and membrane utilization (Stressmann & Moresoli, ). A 2D axisymmetric CFD model was developed using experimental membrane resistance as an input for the simulations.…”

“…The ATF system has several advantages over the TFF system, and has been used in numerous perfusion processes (Clincke, Mölleryd, Zhang, et al, ; Karst, Steinebach, Soos, & Morbidelli, ; Kelly et al, ). However recent studies have shown that product sieving is not improved with ATF under certain conditions (Wang et al, ). CFD model of the complex spatial and temporal variations in pressure and permeate flow in these systems may provide additional insight and understanding of how operational parameters can affect product sieving for perfusion bioreactors.…”

“…The cell culture was then centrifuged at 243 rcf for 20 min (CS‐6R; Beckman Coulter, Brea, CA) to separate cells and larger debris from supernatant. Previously, Wang et al () showed that protein sieving was not impacted after the membranes were exposed to permeate solution that had already passed through a 0.2‐μm membrane or solution containing cell pellet resuspended in permeate. However, when cell culture supernatant containing primarily particles in the 100‐nm size range was introduced to a new hollow fiber membrane, product sieving was severe and almost instantaneous.…”

Manipulation of the sodium‐potassium ratio as a lever for controlling cell growth and improving cell specific productivity in perfusion CHO cell cultures

“…The cell retention device used in all perfusion bioreactors was a polyethersulfone (PES) hollow fiber purchased from Spectrum Laboratories (Rancho Dominquez, CA) operated in either ATF (Repligen, Waltham, MA) or TFF mode using a centrifugal pump (Levitronix, Zurich, Switzerland). The two systems had been previously demonstrated to be interchangeable at the benchtop scale (Wang et al, ). All studies were conducted in 3 L glass stirred tank bioreactors at a 2 L working volume (Applikon Biotechnology, Delft, Netherlands).…”