Monitoring of potential cytotoxic and inhibitory effects of titanium dioxide using on-line and non-invasive cell-based impedance spectroscopy

Titanium dioxide (TiO₂) nanoparticles (NPs) with different sizes and structures were probed for plausible cytotoxicity using electric cell-substrate impedance sensing (ECIS), a non-invasive and on-line procedure for continuous monitoring of cytotoxicity. For insect cells (Spodoptera frugiperda Sf9), the ECIS₅₀ values, i.e., the concentration required to achieve 50% inhibition of the response, differed depending on the size and shape of the TiO₂ nanostructure. The lowest ECIS₅₀ value (158ppm) was observed for the needle shaped rutile TiO₂ (10nm×40nm, 15.5nm nominal particle size), followed by 211ppm for P-25 (34.1nm, 80% anatase and 20% rutile), 302ppm for MTI5 (5.9nm, 99% anatase) and 417ppm for Hombitan LW-S bulk TiO₂ (169.5nm, 99% anatase). Exposure of TiO₂ NPs to UV light at 254nm or 365nm exhibited no significant effect on the ECIS₅₀ value due to the aggregation of TiO₂ NPs with diminishing photocatalytic activities. Chinese hamster lung fibroblast V79 cells, exhibited no significant cytotoxicity/inhibition up to 400ppm with P25, MTI₅ and bulk TiO₂. However, a noticeable inhibitory effect was observed (ECIS₅₀ value of 251ppm) with rutile TiO₂ as cell spreading on the electrode surface was prevented.