Rapid process monitoring & control in mammalian cell culture using off-gas mass spectrometry analysis
May 6-11, 2018
In a concerted effort to investigate the implementation of a process analytical technology (PAT), we have evaluated the applicability of off-gas mass spectrometry (MS) analysis in mammalian cell culture based on the inlet and outlet gases from bioreactors. The limitations of the system & potential applications are also discussed. Compared to other invasive methods that require physical probes inserted directly into the culture (e.g. bio-capacitance probe, Raman spectrometry probe, etc.), the MS only requires gas going in and out of the cell culture which means it has minimal impact on the culture itself. With the Prima BT magnetic sector MS (Thermo Fisher Scientific), multiple gas streams can be analyzed (i.e. multiple bioreactors can be connected to the same Prima BT MS) which could reduce analytical equipment footprint (c.f. other equipment that may require 1 equipment per bioreactor). Distance between bioreactors and the MS is also not an issue given a high enough gas flow and a long enough gas tubing connection to the MS, i.e. the MS can be placed a distance away or even a different site from where all the bioreactors are situated. Our data showed that small changes in the gas traces (O2, CO2, N2 & Ar) on the MS, down to 0.001% mol, can be captured during the following events: 1) feed media addition (containing surfactant) 2) antifoam addition 3) any gas perturbation caused by external factors (non-culture related; gas supply leak or loss) 4) metabolic changes in the cell culture The MS data from two replicate 5L benchtop glass bioreactor runs are very comparable, as is the offline data between them; this indicates that the MS data can be used reliably to identify process deviations during bioreactor runs and be used as a convenient way to evaluate batch to batch variation, within predefined specifications, for robust manufacturing. We have also demonstrated that the same MS setup in the benchtop experiments, with minor modifications, can be applied in a 50L single-use bioreactor (SUB). We would also report that there are technical considerations with respect to the feasibility of integrating this system to the various cell culture platforms. The data so far suggests that the off-gas MS analysis can be: 1) incorporated as a feedback control to determine feed addition rates; 2) used to correlate the growth and perhaps viability of the culture with the MS gas traces; 3) identify cell culture contamination; 4) used to correlate cellular metabolic activity in the culture with the MS gas traces from the O2 & CO2; 5) used to elucidate more detailed metabolic states by analyzing volatile organic carbons (VOCs). In conclusion, we believe that our work presented here will be of significant relevance to the cell culture community who are keen adopters of PAT and its practical implementation.
Hai-Yuan Goh, Ajoy Velayudhan, Michael Sulu, Graham Lewis, and Graham Josland, "Rapid process monitoring & control in mammalian cell culture using off-gas mass spectrometry analysis" in "Cell Culture Engineering XVI", A. Robinson, PhD, Tulane University R. Venkat, PhD, MedImmune E. Schaefer, ScD, J&J Janssen Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/ccexvi/85