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A comparison of the phototoxic potency of six types of TiO2 nanoparticles
Citation:
BOYES, W. K., K. SANDERS, L. DEGN, R. M. ZUCKER, W. R. MUNDY, B. Zhao, AND J. Roberts. A comparison of the phototoxic potency of six types of TiO2 nanoparticles. Presented at Society of Toxicology (SOT) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
These experiments demonstrate that TiO2 nanoparticles become phototoxic when exposed to UVA radiation, with potency dependent on size and/or crystal form.
Description:
Nanoparticles,such as nano-TiO2, are often photo active and can become photo toxic by the generation of reactive oxygen species (ROS) and free-radical oxidative damage to surrounding tissues. Because the retina is the only part of the central nervous system directly exposed to light, the retinal pigment epithelium (RPE) is an important site of photo reactivity. A human-derived RPE cell line (ARPE-19) was exposed to six types of nano-TiO2 and then observed after exposure to UVA radiation. The TiO2 nanoparticles (anatase, 10nm, 32nm, and 200nm; DeGussa, 27 nm; and rutile, 30-40 nm and 200-400 nm) were suspended in DMEM/F12 with 10% fetal bovine serum, sonicated, and characterized by dynamic light scattering. Cells were treated with 0, 0.3,1,3,10,30, or 100 ug/ml TiO2 in media for 24 hrs and then either exposed to UVA radiation (7.53 J/cm2) or kept in the dark (control condition). Cytotoxicity was assessed after 24 hrs by a live/dead assay (calcein-AM/propidium iodide) and flow cytometry. Live/dead assays indicated that cells exposed to higher concentrations of TiO2 with UVA radiation showed significantly lower viability than dark controls, but the degree of response varied by Ti02 type. The 10 nm anatase and 27 nm DeGussa were the most phototoxic compounds tested (LC50 with UVA < 10 ug/m1), while the 200 nm anatase and 200-400 nm rutile were the least phototoxic. Flow cytometry showed that UVA radiation in the presence of Ti02 decreased the cell count, increased cell death, and increased ROS (as measured by Mitosox probe) relative to control cells that had Ti02 but no UVA. These experiments demonstrate that TiO2 nanoparticles become phototoxic when exposed to UVA radiation, with potency dependent on size and/or crystal form.