An inverse approach to determine solute and solvent permeability parameters in artificial tissues

This study presents a generic numerical model to simulate the coupled solute and solvent transport in tissue sections during addition and removal of chemical additives or cryoprotective agents (CPA; dimethylsulfoxide or DMSO). Osmotic responses of various tissue cells within the artificial tissue are predicted by the numerical model with three model parameters: Permeability of the tissue cell membrane to water (Lp), permeability of the tissue cell membrane to the solute or CPA (omega), and the diffusion coefficient of the solute or CPA in the extracellular space (D). By fitting the model results with published experimental data on solute/water concentrations at various locations within an artificial tissue, we were able to determine the permeability parameters of artificial tissue cells in the presence of 1.538 M DMSO. Lp and omega were determined at three different locations within the artificial tissue assuming a constant value of solute diffusivity (D = 1.0 x 10(-9) m2/s). The best fit values of Lp ranged from 0.59 x 10(-14) to 4.22 x 10(-14) m3/N-s while omega ranged from 0 to 6.6 x 10(-13) mol/N-s. Based on these values of Lp and omega, the solute reflection coefficient, sigma = 1 - omegav(-)CPA/Lp, ranged from 0.9923 to 1.0. The relative values of omega and sigma suggest that the artificial tissue cells are relatively impermeable to DMSO (or omega approximately 0 and sigma approximately 1.0). This observation was used to modify our model to predict the values of Lp and D assuming omega = 0 and sigma = 1.0. The best fit values of Lp ranged from 640 x 10(-14) to 2.1 x 10(-14) m3/N-s while D ranged from 0.63 x 10(-9) to 1.52 x 10(-9) m2/s. The permeability parameters obtained in the present study represent the first such effort for artificial tissues.