Application of dielectric spectroscopy for monitoring high cell density in monoclonal antibody producing CHO cell cultivations

Abstract

The application of dielectric spectroscopy was frequently investigated as an on-line cell culture monitoring tool; however, it still requires supportive data and experience in order to become a robust technique. In this study, dielectric spectroscopy was used to predict viable cell density (VCD) at industrially relevant high levels in concentrated fed-batch culture of Chinese hamster ovary cells producing a monoclonal antibody for pharmaceutical purposes. For on-line dielectric spectroscopy measurements, capacitance was scanned within a wide range of frequency values (100-19,490 kHz) in six parallel cell cultivation batches. Prior to detailed mathematical analysis of the collected data, principal component analysis (PCA) was applied to compare dielectric behavior of the cultivations. PCA analysis resulted in detecting measurement disturbances. By using the measured spectroscopic data, partial least squares regression (PLS), Cole-Cole, and linear modeling were applied and compared in order to predict VCD. The Cole-Cole and the PLS model provided reliable prediction over the entire cultivation including both the early and decline phases of cell growth, while the linear model failed to estimate VCD in the later, declining cultivation phase. In regards to the measurement error sensitivity, remarkable differences were shown among PLS, Cole-Cole, and linear modeling. VCD prediction accuracy could be improved in the runs with measurement disturbances by first derivative pre-treatment in PLS and by parameter optimization of the Cole-Cole modeling.

Dielectric spectroscopy‐based estimation ofVCDinCHOcell culture

“…Especially during the model validations with the test set, the three multivariate regression models showed a remarkable reduction in prediction errors, which ranged from a 64 to 79% improvement over that of the simple Cole‐Cole approach. This is generally in agreement with previous studies …”

“…LWPLS) in their functional form. These features are what allow us to differentiate our study from those of others . The first three batches (B1, B2 and B3) were used as a calibration set to build the regression model, and the remaining two batches (B4 and B5) were utilized as a test set to validate the prediction power of the constructed models.…”

“…This is generally in agreement with previous studies. 34,39,42 However, it was also evident in Fig. 6(B) that, despite the improvement, there were still undesirable deviations between estimations and off-line measurements, especially after the stationary phases of CHO cell cultures.…”

“…One possible remedy might be to periodically measure some of the parameters included in Equations (2)-(4) of the course of the culture, for example cell radius. 34,39,42 The first three batches (B1, B2 and B3) were used as a calibration set to build the regression model, and the remaining two batches (B4 and B5) were utilized as a test set to validate the prediction power of the constructed models. The results obtained from these models are presented in Fig.…”

The Application of Dielectric Spectroscopy and Biocalorimetry for the Monitoring of Biomass in Immobilized Mammalian Cell Cultures

“…At low volume fractions non-biological solid particles or dead cells, with permeable membrane, do not interfere with the dielectric signal [18]. It has been successfully shown that suspension cultures can be monitored on-line using single frequency measurements [19,20] or frequency scans [16,17] in stirred tank reactors.…”