Abstract
Age-related macular degeneration (AMD) is a prevalent ocular pathology affecting mostly the elderly population. AMD is characterized by a progressive retinal pigment epithelial (RPE) cell degeneration, mainly caused by an impaired antioxidative defense. One of the AMD therapeutic procedures is injecting healthy RPE cells into the subretinal space. For this purpose, there is a need for pure, healthy RPE cell suspensions. In this article, we present an experimental approach to electrically characterize RPE cells, aiming to demonstrate the possibility of separating healthy RPE cells from a mixture of healthy/oxidized cells by dielectrophoresis. In order to find out the relevant conditions to create an in-vitro AMD cellular model, BPEI-1 rat RPE cells were exposed to hydrogen peroxide and evaluated in terms of cell viability by various methods (microscopic imaging, impedance-based real-time cell analysis, MTS assay). Then, healthy and oxidized cells were characterized by recording their dielectrophoretic spectra, based on which electric cell parameters (crossover frequency, membrane conductivity and permittivity, and cytoplasm conductivity) were computed. A COMSOL simulation was performed on a theoretical microfluidic-based dielectrophoretic separation chip using these parameters. By increasing the hydrogen peroxide concentration, we found that the first crossover frequency was shifted toward lower values, and the cell membrane permittivity progressively increased. These changes were attributed to progressive membrane peroxidation since they were diminished when measured on cells treated with the antioxidant N-acetylcysteine. Moreover, the changes in the crossover frequency showed to be enough for the healthy cells to be efficiently separated, as demonstrated by simulations.