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Nano TiO2: an assessment of potential phototoxicity in retinal pigment epithelial cells in vitro.
Citation:
BOYES, W. K., K. Sanders, L. Degan, W. R. MUNDY, R. M. ZUCKER, B. Zhao, AND J. Roberts. Nano TiO2: an assessment of potential phototoxicity in retinal pigment epithelial cells in vitro. Presented at Society of Toxicology 49th Annual Meeting, Salt Lake City, UT, March 07 - 11, 2010.
Impact/Purpose:
These experiments demonstrate that TiO2 nanoparticles can accumulate in ARPE-19 cells within hours, persist for weeks, and may become phototoxic when exposed to visible or UV wavelengths.
Description:
Nanoparticles often have properties, such as photoactivity, that differ from those of their bulk counterparts. Photoactive materials can become phototoxic by the generation of reactive oxygen species and free-radical oxidative damage to surrounding tissues. The retina is the only part of the central nervous system directly exposed to light, and the retinal pigment epithelium (RPE) is a site ofphotoreactivity. A human-derived RPE cell line (ARPE-19) was exposed to nano-TiO2, and observed over a brief or an extended time course, and after exposure to visible light or UV radiation. TiO2 nanoparticles (rutile, 30-40 nm, and anatase, 32 nm) were suspended in DMEM/F12 with 10% fetal bovine serum (FBS), sonicated, and characterized by dynamic light scattering.Cells were plated on culture slides, treated with 15ug/ml nano-TiO2,and observed under phase microscopy from 5 min to 3 days. Particles immediately began to settle, and by 3 days large agglomerates were seen inside cells, often in ring structures around the nucleus. In a longer study, cells were treated with 0, 10, or 30 ug/ml nano-TiO2 and photographed for up to 25 days. The ring structures were visible in TiO2 flasks at 24 hours and persisted in viable cells for up to 25 days. Finally, cells were exposed to 0,1, 5,10, 25, and 50 ug/ml TiO2(anatase) in DMEM/F12 with 10% FBS for 24 hrs. Cells were switched to HBSS and exposed to dark, visible light (1 hr), or UV radiation (15 min), then returned to media containing either 10% or 2% FBS. The next day cytotoxicity was assessed by MTS and live/dead assays (calcein-AM/propidium iodide). In 2% FBS, cells exposed to 25 or 50ug/ml TiO2 and visible light or UV radiation showed significantly lower MTS and lower % viability than dark controls. These experiments demonstrate that TiO2 nanoparticles can accumulate in ARPE-19 cells within hours, persist for weeks, and may become phototoxic when exposed to visible or UV wavelengths.