On-line Measurements and Control of Viable Cell Density in Cell Culture Manufacturing Processes using Radio-frequency Impedance

Abstract

In this work, radio-frequency (RF) impedance is reviewed as a method for monitoring and controlling cell culture manufacturing processes. It is clear from the many publications cited that RF Impedance is regarded as an accurate and reliable method for measuring the live cell bio-volume both on-line and off-line and the technology is also sutable for animal cells in suspension, attached to micro-carriers or immobilized in fixed beds. In cGMP production, RF Impedance is being used in three main areas. Firstly, it is being used as a control instrument for maintaining consistent perfusion culture allowing the bioreactor to operate under optimum conditions for maximum production of recombinant proteins. In the second application it has not replaced traditional off-line live cell counting techniques but it is being used as an additional monitoring tool to check product conformance. Finally, RF Impedance is being used to monitor the concentration of live cells immobilized on micro-carriers or packed beds in cGMP processes where traditional off-line live cell counting methods are inaccurate or impossible to perform.

Process control in cell culture technology using dielectric spectroscopy

“…These parameters are also important for subsequent legally required process validation [Li et al, 2006]. Many cell culture based processes are operated in perfusion or fed-batch mode, where control of the perfusion or feed addition rate is required to maximize recombinant protein production [Carvell and Dowd, 2006]. Biological systems are very sensitive to many process changes.…”

“…Infra-red sensors have also been described, but their range of cell concentrations is rather limited. Laser turbidity measurements are suitable for high cell density cultures [Carvell and Dowd, 2006]. Until 2002, most methods for the monitoring of cell concentrations were not applicable to immobilized cell cultures using microcarriers or other fixed bed carriers.…”

“…that lead to significant separation and purification issues "downstream" [Rathore et al, 2008]. A promising tool for the on-line monitoring of cell cultures and biomass properties is DS, allowing non-invasive and non-destructive continuous process monitoring in bioreactors for suspension cultures and even cells attached to solid carriers [Carvell and Dowd, 2006]. DS has been used industrially for some time to monitor the viable cell density for example of yeast in the brewing process [Heggart et al, 2000, Austin et al, 1994.…”

“…DS has been used industrially for some time to monitor the viable cell density for example of yeast in the brewing process [Heggart et al, 2000, Austin et al, 1994. The application of DS has already been discussed in the context of PAT [Boudreau andBenton, 2008, Gnoth et al, 2007] and has been suggested as a possibly accurate and reliable method for online monitoring of viable cell density in cell manufacturing processes [Carvell and Dowd, 2006]. Examples include cell cultivation on solid surfaces, on microcarriers in suspension, on porous glass carriers in fluidized bed reactors, and on porous discs in a fixed bed reactor.…”

“…Examples include cell cultivation on solid surfaces, on microcarriers in suspension, on porous glass carriers in fluidized bed reactors, and on porous discs in a fixed bed reactor. Reviewed cell types include bacteria, yeast, mammalian, and insect cells [Carvell, 2008, Carvell and Dowd, 2006, Ducommun et al, 2001, Fehrenbach et al, 1992, Noll and Biselli, 1998, Sarra et al, 1996, Zeiser et al, 1999.…”