An impedance-based high-throughput method for evaluating the cytotoxicity of nanoparticles

Impedance-based assays can constitute a reliable alternative to the conventional methods used in nanotoxicology due to the important advantages of being label-free and monitoring the cells in real-time. In this study, the suitability of impedance-monitoring for the screening of nanoparticle (NP)-induced cytotoxicity was assessed. The effect of titanium dioxide (TiO2)-NPs on cellular proliferation, viability, spreading, and detachment from substrate was evaluated by continuous impedance-based measurements made with an xCELLigence system. Fibroblasts seeded in microelectrode-embedded E-plates were exposed to spherical anatase nano-TiO2 (5, 10, and 40 nm in diameter) for up to 120 h. An alternative excitation signal (20 mV control voltage amplitude) was applied at 10, 25, and 50 kHz to the microelectrodes in the E-plates. Cells attached to the electrode surfaces act as insulators and lead to an increase in impedance. For validating the impedance-method, Trypan Blue exclusion and ultrahigh resolution imaging (URI) were employed. The general trend observed was a decrease in impedance following exposure to TiO2-NPs. Impedance-based results were in most instances in accordance with those from the Trypan Blue exclusion and URI assays indicating that the impedance-based approach has merit. Further studies are needed to validate it as a high-throughput method for evaluating NPs' cytotoxicity.