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

Harriet Cole,Ian Marison,Aurélie Demont

doi:10.3390/pr3020384

Abstract

The purpose of this study was to introduce dielectric spectroscopy and biocalorimetry as monitoring methods to follow immobilised Chinese Hamster Ovary (CHO) cell culture development. The theory behind both monitoring techniques is explained and perfusion cultures are performed in a Reaction Calorimeter (eRC1 from Mettler Toledo) as an application example. The findings of this work show that dielectric spectroscopy gives highly reliable information upon the viable cell density throughout the entire culture. On the other hand, the RC1 could only provide accurate data from day 5, when the cell density exceeded 4 × 106 vcells∙mL−1 (viable cell per mL) working volume (WV). The method validation showed the limit of detection (LOD) for 1.4 L cultures to be 8.86 × 106 vcells∙mL−1, a viable cell density commonly achieved in fed-batch and the early stages of a perfusion culture. This work suggests that biocalorimetry should be possible to implement at industrial scale to monitor CHO cell cultures.

Highlights

Mammalian cells are commonly used to produce biopharmaceuticals as they are capable of correct glycosylation and other post-translational modifications of therapeutic proteins [1,2,3,4]
Providing the cells grow constantly at 0.62 days−1, without a lag phase, the full microcapsule core colonisation should be achieved after 11.3 days
Immobilised cell cultures have an additional barrier to real-time monitoring as the cells are not directly available for analysis

Summary

Introduction

Mammalian cells are commonly used to produce biopharmaceuticals as they are capable of correct glycosylation and other post-translational modifications of therapeutic proteins [1,2,3,4]. Perfusion cultures involve continuously supplying the culture with fresh culture media whilst continuously removing the spent media at an identical rate, ensuring the working volume remains constant This culture type has the advantage to obtain high cell densities whilst continuously supplying the cells with all the essential nutrients and removing all the waste by-products. The cells are usually retained within the reactor by a cell separating device such as a spin filter, cross flow filter, hydrocyclone or acoustic cell settler, Figure 1A. These cell separators represent an added cost, can gradually foul or are difficult to scale- up. A simple mesh is sufficient to extract the spent media as represented in Figure 1B [5]

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