Theoretical and experimental analyses of optimal experimental design for determination of hydraulic conductivity of cell membrane.

Determination of cell hydraulic conductivity (Lp) is required to predict the optimal conditions for cell cryopreservation. One of the critical procedures associated with the determination of Lp is to measure the kinetics of cell volume change in response to a sudden cell exposure to anisosmotic media until the cells achieve an osmotic equilibrium state. To achieve accurate measurement, it should be ensured that (1) the cell osmotic equilibration process is sufficiently slow, and (2) the total cell volume change (ΔV) is much larger than the resolution of the measuring device (δ). In this article, a cell's half volume excursion time (t*) was defined as the time in which osmotically active cell water volume increases or decreases by half of its maximum change. Based on the water transport equations, a series of analytical solutions were derived. The t* and ΔV were expressed as functions of 2 control variables: initial intracellular osmolality (Mo) and extracellular osmolality (Me), and the effects of Me and Mo on t* and ΔV were predicted theoretically. The predictions were confirmed by performing experiments using two different cell types. In the light of this study, a strategy to optimize the experiment design for the Lp determination is suggested.