DFG Priority Program SPP 2170 “InterZell” – Project “CHOLife”: Multiscale experimental analysis and simulation of lifelines in bioreactors to study their impact on the cultivation performance of Chinese Hamster Ovary (CHO) cells
Large-scale bioreactors with working volumes up to 22,000 L are frequently exposed to dynamic cultivation conditions that create spatial and temporal gradients in mixing. These variations cause a decline in cellular performance, which ultimately results in lower product quality and quantity. Precise and reliable process control is critical for biopharmaceutical production of vaccines and monoclonal antibodies, as well as for understanding the impact of dynamically changing environments on cells. For the detailed understanding of cultivation processes it is indispensable to get deep insights into the overall and local hydrodynamics with high spatial and temporal resolution.
CHOLife tackles the scale-up problem linking the unique access to a transparent 15,000 L cell culture bioreactor (Institute of Multiphase Flows, TUHH Hamburg, IMS) with the development of a novel scale-up device (Institute of Biochemical Engineering, Stuttgart, IBVT) in order to predict industrial-scale performance of IgG1 producing CHO cells. In essence, three dimensional flow trajectories and lifelines will be measured at the IMS and mimicked in the novel scale-up simulator of IBVT. The close cooperation of both parties ensures a successful scale-down of large-scale conditions and an equally successful prediction of large-scale performance of CHO cells cultured in the novel scale-up simulator.
One method of gaining insight into complex hydrodynamic flow patterns and compartmentalization is by means of the (de)colorization method, which is based on phenolphthalein or bromothymol blue in an acrylic glass bioreactor. However, the lack of optical access into generic bioreactors requires an alternative analysis. Industrially used fixed probes at the reactor wall cannot provide information on spatiotemporal gradients or the cell's residence time in different zones of the reactor.
To overcome this limitation, Lapin et al. proposed the "Traveling along the Lifelines of Single Cells" approach, which uses a numerical method. This Lagrangian analysis was recently experimentally scrutinized on laboratory-scale through the 4D-Particle Tracking Velocimetry (4D-PTV) method demonstrating detailed results regarding the flow-following capability of Lagrangian particles.
On production scale, a combination of sensor systems integrated into a mobile, enclosed and neutrally buoyant Lagrangian Sensor Particle (LSP) offers a deeper understanding of complex flow patterns inside a bioreactor by recording data alongside its trajectory and thereby mimicking the movement of a cell.