title: On-line monitoring of responses to nutrient feed additions by multi-frequency permittivity measurements in fed-batch cultivations of CHO cells.
abstract: Changes in the nutrient availability of mammalian cell cultures are reflected in the beta-dispersion parameter characteristic frequency (f ( C )) and the on-line dual frequency permittivity signal. Multi-frequency permittivity measurements were therefore evaluated in fed-batch cultivations of two different CHO cell lines. Similar responses to nutrient depletions and discontinuous feed additions were monitored in different cultivation phases and experimental setups. Sudden increases in permittivity and f ( C ) occurred when feed additions were conducted. A constant or declining permittivity value in combination with a decrease in f ( C ) indicated nutrient limitations. f ( C ) correlated well with changes in oxygen uptake rate when cell diameter remained constant, indicating that metabolic activity is reflected in the value of f ( C ). When significant cell size changes occurred during the cultivations, the analysis of the beta-dispersion parameters was rendered complex. For the application of our findings in other systems it will be hence required to conduct additional off-line measurements. Based on these results, it is hypothesized that multi-frequency permittivity measurements can give information on the intracellular or physiological state in fed-batch mode. Similar observations were made when using different cell lines and feeding strategies, indicating that the findings are transferable to other cell lines and systems. The results should lead to an improved understanding of routine fed-batch processes. Additional studies are, however, required to explore how these observations can be used for fed-batch process development and optimization.
authors.affiliation: F. Hoffmann-La Roche AG, Basel, Switzerland, sven.ansorge@nrc.ca.
authors.forename: Sven
authors.initials: S
authors.lastname: Ansorge
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Esteban
authors.forename: Georg
authors.initials: G
authors.lastname: Schmid
references.citation: Adv Biol Med Phys. 1957;5:147-209
references.pmid: 13520431
references.citation: Biotechnol Bioeng. 2005 Jan 20;89(2):164-77
references.pmid: 15593097
references.citation: Biotechnol Bioeng. 1990 Oct 20;36(8):839-48
references.pmid: 18597283
references.citation: Biotechnol Prog. 2008 Jan-Feb;24(1):158-65
references.pmid: 18052336
references.citation: Cytotechnology. 2007 Dec;55(2-3):115-24
references.pmid: 19003001
references.citation: Biotechnol Bioeng. 1992 Dec 20;40(11):1337-42
references.pmid: 18601089
references.citation: Biotechnol Bioeng. 1996 Apr 5;50(1):36-48
references.pmid: 18626897
references.citation: Biotechnol Bioeng. 2002 Feb 5;77(3):316-23
references.pmid: 11753940
references.citation: Biotechnol Bioeng. 1996 Oct 20;52(2):271-89
references.pmid: 18629894
references.citation: Dev Biol Stand. 1987;66:357-60
references.pmid: 3582764
references.citation: Biotechnol Bioeng. 2003 Dec 5;84(5):597-610
references.pmid: 14574694
references.citation: Biotechnol Bioeng. 1998 Jun 5;58(5):464-77
references.pmid: 10099282
references.citation: Cytotechnology. 2000 Oct;34(1-2):59-70
references.pmid: 19003381
references.citation: Biotechnol Bioeng. 1999 Apr 5;63(1):122-6
references.pmid: 10099588
references.citation: Biotechnol Prog. 2000 Sep-Oct;16(5):803-8
references.pmid: 11027174
references.citation: Nat Biotechnol. 2004 Nov;22(11):1393-8
references.pmid: 15529164
references.citation: Biotechnol Bioeng. 2006 Dec 20;95(6):1228-33
references.pmid: 16865737
references.citation: Biotechnol Lett. 2005 Apr;27(7):511-7
references.pmid: 15928859
references.citation: Biotechnol Bioeng. 2001 Mar 5;72(5):515-22
references.pmid: 11460241
references.citation: J Biotechnol. 1998 Aug 27;63(3):187-98
references.pmid: 9803533
references.citation: Biotechnol Prog. 2010 Jan-Feb;26(1):272-83
references.pmid: 19899122
references.citation: J Biotechnol. 1992 May;23(3):303-14
references.pmid: 1368248
references.citation: J Immunol Methods. 1996 Aug 14;194(2):191-9
references.pmid: 8765172
references.citation: Biotechnol Bioeng. 2000 May 20;68(4):381-8
references.pmid: 10745206
references.citation: Phys Med Biol. 1987 Aug;32(8):933-70
references.pmid: 3306721