A novel approach for using dielectric spectroscopy to predict viable cell volume (VCV) in early process development

Abstract

Online monitoring of viable cell volume (VCV) is essential to the development, monitoring, and control of bioprocesses. The commercial availability of steam-sterilizable dielectric-spectroscopy probes has enabled successful adoption of this technology as a key noninvasive method to measure VCV for cell-culture processes. Technological challenges still exist, however. For some cell lines, the technique's accuracy in predicting the VCV from probe-permittivity measurements declines as the viability of the cell culture decreases. To investigate the cause of this decrease in accuracy, divergences in predicted vs. actual VCV measurements were directly related to the shape of dielectric frequency scans collected during a cell culture. The changes in the shape of the beta dispersion, which are associated with changes in cell state, are quantified by applying a novel “area ratio” (AR) metric to frequency-scanning data from the dielectric-spectroscopy probes. The AR metric is then used to relate the shape of the beta dispersion to single-frequency permittivity measurements to accurately predict the offline VCV throughout an entire fed-batch run, regardless of cell state. This work demonstrates the possible feasibility of quantifying the shape of the beta dispersion, determined from frequency-scanning data, for enhanced measurement of VCV in mammalian cell cultures by applying a novel shape-characterization technique. In addition, this work demonstrates the utility of using changes in the shape of the beta dispersion to quantify cell health. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:479–487, 2014

Impact of apoptosis on the on-line measured dielectric properties of CHO cells

“…Downey et al reported changes in the shape of the beta dispersion curve in the decline phase of a fed-batch CHO cultivation [34] which were probably caused by similar cell deathrelated processes as in our study. In our study, the shift in the f C of the Cole-Cole model after the induction of apoptosis further confirmed the hypothesis that the shape of the capacitance spectrum is vastly affected by apoptosisinduced dielectric changes.…”

High titer oncolytic measles virus production process by integration of dielectric spectroscopy as online monitoring system

“…The use of DS to monitor virus production in suspension cell lines is well established for example, for the baculovirus production system (Downey et al, 2014;Justice et al, 2011;Negrete et al, 2007).…”

“…It is widely used in yeast fermentation (Asami, Gheorghiu, & Yonezawa, 1999;Huang, Holzel, Pethig, & Xiao, 1992) and has also been used to monitor the expansion of animal cells, the differentiation of stem cells, and virus-based production processes (Downey, Graham, Breit, & Glutting, 2014;Druzinec et al, 2013;Justice et al, 2011;Negrete, Esteban, & Kotin, 2007). It is widely used in yeast fermentation (Asami, Gheorghiu, & Yonezawa, 1999;Huang, Holzel, Pethig, & Xiao, 1992) and has also been used to monitor the expansion of animal cells, the differentiation of stem cells, and virus-based production processes (Downey, Graham, Breit, & Glutting, 2014;Druzinec et al, 2013;Justice et al, 2011;Negrete, Esteban, & Kotin, 2007).…”

On-Line Monitoring of Biomass Concentration Based on a Capacitance Sensor: Assessing the Methodology for Different Bacteria and Yeast High Cell Density Fed-Batch Cultures

“…Continuous measurement of cell concentration is technically feasible by means of several techniques such as laser turbidimetry, suspended solid concentration analysis, in situ microscopy, near-infrared spectroscopy, laser light scattering analysis, fluorescence, flow cytometry, dielectric spectroscopy and capacitance measurements, as well as with optical density scanners (Yamane et al, 1991;Macaloney et al, 1997;Xiong et al, 2008;Kiviharju et al, 2008;Dabros et al, 2009;Díaz et al, 2010;Downey et al, 2014;Wyre and Overton, 2014).…”