Evaluation of an online biomass probe to monitor cell growth and cell death

Background The estimation of cell density and cell viability of mammalian cell lines in cell culture has traditionally been performed using the exclusion dye trypan blue that stains “dead” cells when their cell membrane is damaged. In large scale cell cultures using bioreactors this estimation is performed off-line. The online biomass probe is based on the principle that under the influence of an electric field between two electrodes, ions in suspension migrate toward the electrodes. The cell plasma membrane is non-conductive so that the cells with intact plasma membranes are polarized and act as tiny capacitors and it has been shown that capacitance increases as the cell concentration does. The measurement is based on the linear relationship between the permittivity difference ε1ε2 and the viable biomass concentration as it has been described by Ansorge et al. [1]. This study compares the data obtained using the biomass probe against the cell counts and viability determined by trypan blue exclusion with two GS-CHO cell line productions in bioreactors. Apoptosis determination measurements using rhodamine-123 and pancaspase activation by flow cytometry will be compared to permittivity values.