Evaluating Membrane Electrical Properties of SMMC7721 Cells with TiO2 NPs Applications to Cytotoxicity by Dielectric Spectroscopy

Abstract

Titanium dioxide nanoparticles (TiO2 NPs) represent one of the most frequently applied nanomaterials in numerous areas of daily life. Recent studies show that TiO2 exposure increases the occupational risk of liver injury and inflammation, and even liver cancer to the workers of factories handling these NPs. However, the potential risks and biophysical effects of TiO2 on hepatic cells need extensive evaluation. To this end, we explored the electrophysiological changes in the human liver cancer cell line SMMC7721 following exposure to TiO2 NPs. TiO2 NPs decreased the first (Δε1) and second dielectric relaxation intensity (Δε2) of the SMMC7721 cells by 6.62% and 0.86% respectively, and significantly increased the first characteristic frequency (fc1, 4.82%) and the first Cole–Cole parameter (β1, 1.24%). The double spherical-shell model showed that TiO2 NPs significantly lowered the permittivity of unit-membrane and capacitance, as well as the conductivity of extracellular fluid, cytoplasm, and nuclear contents compared to the untreated control. Conclusively, this study revealed that TiO2 NPs induce cytotoxic effects by disrupting the permeability and electrical conductivity of unit membranes. Further, we report that dielectric spectrum combined with model parameter analysis can evaluate the bioelectrical effects of TiO2 NPs on human liver cancer cells.