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 (L-p), 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. were determined at three different locations within the artificial tissue assuming a constant value of solute diffusivity ( D = 1.0 x 10(-9) m(2)/s). The best fit values of L-p ranged from 0.59 x 10(-14) to 4.22 x 10(-14) m(3)/N-s while. ranged from 0 to 6.6 x 10(-13) mol/N-s. Based on these values of L-p and omega, the solute reflection coefficient, sigma = 1 - omega(nu) over bar (CPA)/L-p ranged from 0.9923 to 1.0. The relative values of. and s suggest that the artificial tissue cells are relatively impermeable to DMSO (or omega approximate to 0 and sigma approximate to 1.0). This observation was used to modify our model to predict the values of Lp and D assuming. = 0 and s = 1.0. The best fit values of L-p ranged from 640 x 10(-14) to 2.1 x 10(-14) m(3)/ N-s while D ranged from 0.63 x 10(-9) to 1.52 x 10(-9) m(2)/s. The permeability parameters obtained in the present study represent the first such effort for artificial tissues.