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Charakterisierung und Modellierung des Wachstums von adhärenten tierischen Zellen in Microcarriersystemen am Beispiel von Madin Darby Canine Kidney Zellen (MDCK).


Bock,  A.
Bioprocess Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society;

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Bock, A. (2003). Charakterisierung und Modellierung des Wachstums von adhärenten tierischen Zellen in Microcarriersystemen am Beispiel von Madin Darby Canine Kidney Zellen (MDCK). Diploma Thesis, Otto-von-Guericke-Universität, Magdeburg.

Cite as:
The growth of adherent animal cells (Madin Darby Canine Kidney, ECACC) on a microcarrier system (Cytodex 1, Amersham Biosciences) could be described by using a simple unstructured, non-segregated model. At first some necessary model parameters had be determined in different experiments or had be found in several publications. The literature query on the topic “modelling of the cell growth of MDCK cells” was not successful. Therefore, only parameters derived from the evaluation of own experiments were used. Additionally, a non-linear regression of parameters without constraints after the Nelder-Meads simplex algorithm was applied. Due to not satisfactory fits of the non-linear regression a manual variation of model parameters was applied. In addition to the optimization of parameters several experiments were performed to determine characteristics of the influenza vaccine process. The interactions between the cells and microcarriers were taken into account. Due to the determination of mass and geometric properties of a single living MDCK cell an estimation of the maximal biomass on one microcarrier and in the whole process was possible. However, when calculating the biomass in the process according to the data given by the microcarrier supplier values were too high compared to the measured values. An investigation of the used microcarrier system gave no final answer to the open question of the mass specific surface. Another aim of the thesis was the quantitative determination of the oxygen mass transfer into the medium and the oxygen uptake of the MDCK cells. Thus, the knowledge of the oxygen uptake rates allowed of an estimation of the living biomass concentration in the process using the known on-line signal of oxygen partial pressure (pO2). The estimation of the lactate concentration using the on-line signal of sodium hydroxide consumption should be possible, too. Finally, the model simulation and the experimental data of a standard cultivation showed a good agreement for the substrates (glucose and glutamine), for the metabolites (lactate and ammonia) and also for the consumption of sodium hydroxide. A good fit for the biomass in the process could not be obtained with the model. Thus, the indirect determination of cell numbers in the process through evaluation of trends of metabolites - the main goal of the work – was not achieved. This could be due to an inhomogen sample taking. In the future a modified method of the direct determination of cell numbers using a haemacytometer for immobilized cell cultures could overcome the actual scattering of the biomass data. The modification is a new reference value for the cell numbers. In place of living cells per mL the new unit could be living cells per cm2 or living cells per microcarrier. In this way changes of conditions during sample taking could be compensated. But the new reference value of the biomass requires the determination of the microcarrier concentration in the sample. Further the knowledge about the properties of the used microcarrier system is also essential, especially mean diameter of microcarriers and the mass specific surface or the mass specific particle number for a monodispersed particle system. Additionally, the assumption of qualitative equal cell coverage on microcarriers between bioreactor and sample is necessary.