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Joan E. Roberts, William K. Boyes, Kristen Sanders, Laura L. Degn, Robert Zucker, William R. Mundy, Kevin Dreher, Baozhong Zhao; A Comparison Of The Phototoxic Potency Of Six Types Of TiO2 Nanoparticles. Invest. Ophthalmol. Vis. Sci. 2012;53(14):270.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if there was a correlation between in vitro retinal phototoxic potency and particle parameters (size and surface area) of TiO2 nanoparticles (nano-TiO2).
Retinal pigment epithelial cells (ARPE-19) were treated with six different samples of nano-TiO2 and exposed to UVA radiation. The TiO2 nanoparticles were independently characterized to have mean primary particle sizes and crystal structures of 22 nm anatase/rutile, 25 nm anatase, 31 nm anatase/rutile, 59 nm anatase/rutile, 142 nm anatase, and 214 nm rutile. Particles were suspended in cell culture media, sonicated, and assessed for stability and aggregation by dynamic light scattering. Cells were treated with 0, 0.3, 1, 3, 10, 30, or 100 μg/ml nano-TiO2 in media for 24 hrs and then exposed to UVA (2 hrs, 7.53 J/cm2) or kept in the dark. Viability was assessed 24 hrs after the end of UVA exposure by microscopy with a live/dead assay (calcein-AM/propidium iodide).
Exposure to higher concentrations of nano-TiO2 with UVA lowered cell viability. The 25 nm anatase and 31 nm anatase/rutile were the most phototoxic (LC50 with UVA < 5 μg/ml), while the 142 nm anatase and 214 nm rutile were the least phototoxic. Flow cytometry showed that nano-TiO2 combined with UVA decreased cell viability and increased the generation of reactive oxygen species (ROS, measured by Mitosox).
Treatment with TiO2 nanoparticles and UVA radiation caused phototoxic damage to ARPE-19 cells. The mechanism of phototoxicity apparently involved ROS formation. The LC50 values of different samples of TiO2 under UVA radiation were directly correlated with particle surface area, and indirectly correlated with primary particle size.
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