Explicit modeling subzero dehydration of living cells

As a cell suspension is being frozen, the contained cells will be dehydrated because the water activity in extracellular medium is being lowered. On the basis of ideal solution, the dehydration process has been modeled as the change of cell volumes with time or temperature, driven by the drop of water activity from intracellular to extracellular. At present, the volume change with temperature is the first derivative in widely used models, but the initial cell volume and the initial water activity are not in accordance with the model. Here, we show that this conflict comes from fact that the calculation of water activity is relative to the freezing point of pure water. From this point to the starting freezing point of solution, the cell volume remains constant for no dehydration. This conflict has been resolved as we choose the starting point of cell volume change as the reference temperature for the water activity calculation.