Date: Tuesday, Nov. 12th, 2013
Time: 12:00 pm
Location: TRC 206
Light refreshments will be served at 11:45 am
Dissertation title: Impact of process parameters on product titer and quality attributes during cell culture scale down
Quality by Design and Process Analytical Technology regulatory initiatives aim to achieve consistent production of biopharmaceutical products of predefined quality. Extensive process development studies are imperative to establish such a production process. Currently, these studies are primarily being carried out in bench scale systems. However, bench scale bioreactor studies are costly, tedious and time consuming to set up. An in-house developed, novel high-throughput minibioreactor system shows a significant potential to improve and streamline process development studies. However, in order to fully qualify this system as a scale down model, comparability between the two scales needs to be established. Comparability of product titers and product quality aspects such as glycosylation profile, which is considered to be one of the major product quality attributes, would be of greatest relevance.
Here, we investigate cell culture scale down on monoclonal antibody titers and their N-glycan profiles produced by serum free mammalian cell culture in these two systems. Methods for purification of monoclonal antibody using protein-A chromatography followed by ion exchange chromatography and N-glycan analysis using high pH anion exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) were developed. Structural determination of glycans was done using MALDI TOF mass spectrometry. A comparability experiment indicated that DO (dissolved oxygen) and pH profiles, cell growth, glucose and lactate profiles were similar in bench scale bioreactors and minibioreactors. Although the relative areas of major N-glycans obtained by HPAEC were found to be comparable in two systems, antibody titers in bench scale bioreactor were about 50% higher than in minibioreactor. While investigating this, a noticeable difference in the glutamine consumption in two systems was observed. Evidence in the literature related glutamine consumption to pCO2 levels. In order to investigate the role of pCO2, a novel pCO2 sensor patch was modified for use in mammalian cell culture. This sensor revealed a difference between the pCO2 profiles in both systems. CO2 stripping studies were conducted in order to have comparable pCO2 stripping rate. A comparability study conducted at comparable pCO2 stripping rate showed similar pCO2 profiles and a significant improvement in product titers in minibioreactors was achieved. Finally, the effect of dissolved oxygen (DO) in minibioreactors and bench scale bioreactors was investigated. Effects of DO on cell growth, viability, glucose and lactate profiles, product titers and their N-glycan profiles were found to be comparable. This project attempted to understand the changes that occur during scale down in the cell culture environment, that are significant enough to impact critical process outcomes such as product titer and product quality . This understanding proved to be crucial to provide the comparability of these miniaturized systems with the bench scale systems and to establish them as a scaled down model.