Mammalian cell lines are often used for the industrial production of biopharmaceuticals. Cell banks represent the stock of cell culture in the long run, with the freezing of cells in some way stopping the biological time. From a cell bank we can establish new bioprocesses at any time. In order to ensure the stability of the frozen cell culture, the cells should be properly prepared for freezing, as when ice freezes, ice and crystals form outside and inside the cell and dehydrate, leading to cell damage. To this end, we add fast-penetrating cryoprotectant DMSO, which protects the cells against damage, but at the same time, if it is too high or if cells are too exposed to it, it is toxic for them. In the master's thesis, we tested whether a lower concentration of DMSO could reduce its cell toxicity and thus increase their survival. It was found that at a lower DMSO concentration used between 4.5 and 7 %, higher cell concentrations of up to 100×106 cells/ml could be frozen. We managed to maintain high survival of the cells by preparing a freeze-up suspension in cold conditions, thus extending the time when the DMSO cells could be exposed to freezing. Variability among parallels also greatly decreased.
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