Assessment of anisotropic transmembrane transport coefficient vector of cell-spheroid under inhomogeneous ion concentration distribution fields by electrical impedance tomography

The assessment method of anisotropic transmembrane transport coefficient vector P of a cell-spheroid under inhomogeneous ion concentration fields has been proposed by combining electrical impedance tomography (EIT) with an ion transport model to evaluate the anisotropic transmembrane transport of ions. An element Pi of P represents the transmembrane transport coefficient of the ith part of the cell membrane, which is assessed by the ion transport model from the average conductivity σ̃i of the ith extracellular sector reconstructed by EIT. Anisotropic factor H obtained from Pi is introduced, which represents the anisotropic transmembrane transport. To validate our methodology, the inhomogeneous ion concentration fields are generated by injecting two tonicity-different sucrose solutions (isotonic, hypotonic or hypertonic) from both sides of the cell-spheroid. As a result, the inhomogeneous ion concentration distribution due to the anisotropic transmembrane transport is successfully observed from the reconstructed image by EIT. The anisotropic factor H shows that H = 0.34 ± 0.24 in isotonic and hypertonic combination, H = 0.58 ± 0.15 in isotonic and hypotonic combination and H = 0.23 ± 0.06 in hypertonic and hypotonic combination, respectively. To verify the results obtained by our methodology, the fluorescence ratio F [-] of potassium ions around the cell-spheroid is observed under three combinations as same as the EIT measurement. F shows the anisotropic transmembrane transport with the same trend with the EIT results.