Scaling-Up Vertical-Wheel Bioreactors Based on Cell Aggregate Exposure to Shear Stress and Energy Dissipation Rate

Area of Science:

• Biotechnology
• Cell Biology
• Chemical Engineering

Background:

• Large-scale human pluripotent stem cell (hPSC) production is crucial for clinical applications.
• 3D suspension cultures are effective for hPSC manufacturing but sensitive to hydrodynamic conditions.
• Optimizing bioreactor design and operation is key to maintaining hPSC yield, viability, and quality.

Purpose of the Study:

• Characterize hydrodynamics within vertical-wheel bioreactors (VWBRs) across different sizes and agitation rates.
• Assess the impact of hydrodynamic forces on hPSC aggregation and proliferation.
• Propose Lagrangian-based shear stress and energy dissipation rate (EDR) metrics for improved hPSC manufacturing scale-up.

Main Methods:

• Conducted in silico 3D turbulent flow simulations for 100 mL and 500 mL VWBRs at 20–80 rpm.
• Calculated trajectories and exposures of 200–1,000 micron cell aggregates to shear stress and EDR.
• Performed in vitro culture of ESI-017 hPSCs in VWBRs for 6 days, measuring aggregation efficiency and fold ratios.

Main Results:

• Aggregate size, agitation, and bioreactor size influence cell aggregate exposure to EDR and shear stress.
• EDR significantly affects hPSC aggregation efficiency, cell counts, and aggregate size.
• EDR impacts total fold ratio, with minor effects on daily fold ratios; shear stress has minimal impact.

Conclusions:

• Trajectory-based EDR exposure offers a superior basis for VWBR scale-up compared to volume-averaged EDR.
• Shear stress does not significantly influence hPSC aggregation, proliferation, or expansion under the tested conditions.
• Lagrangian metrics provide a more accurate assessment of hydrodynamic effects on hPSC cultures for scalable manufacturing.