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The genotoxicity of titanium dioxide and cerium oxide nanoparticles in vitro
Citation:
Prasad, R. Y., K. WALLACE, A. H. TENNANT, K. T. KITCHIN, A. D. KLIGERMAN, AND C. F. BLACKMAN. The genotoxicity of titanium dioxide and cerium oxide nanoparticles in vitro. Presented at Genetics & Environmental Mutagenesis Society, Chapel Hill, NC, October 06, 2009.
Impact/Purpose:
Investigate acellular and cellular effects of selected nano-mater
Description:
The use ofengineered nanoparticles in both current and future consumer products is steadily increasing. However, the health effects of exposure to these nanoparticles are not thoroughly understood. Recently, particular emphasis has been placed on particle characterization and the elimination of confounding factors, such as nanoparticles binding to polystyrene surfaces. This study looked at a series of eight engineered nanoparticles of various sizes and manufacturers (six titanium dioxide and two cerium oxide particles) with respect to their genotoxicity. Each particle was characterized by its crystal structure, size in dry form, as well as size and zeta-potential in suspensions used for the assays (acellular: phosphate buffered saline [PBS]; cellular: keratinocyte growth medium [KGM] with 0.1% BSA). Immuno spin trapping (1ST), an acellular, high-throughput assay using the nitrone spin trap DMPO was used to determine oxidative modification of DNA. Based on the results ofthe 1ST assay, a subset of particles was tested in h~man bronchial epithelial cells (BEAS-2B) cultured in KGM defined medium. Trypan blue dye exclusion was used to establish a dose-response curve of cell toxicity. The single cell gel electrophoresis (comet) assay was used to assess DNA single-strand breaks in culture after 24 hr treatment with different concentrations ofnanoparticles (lO, 50, 100, 150 ug/ml), Degussa P25 AEROXIDE® Ti02 (size 27.5 nm) and Alfa Aesar Ti02 (size 32 nm) caused significant DNA oxidative damage at concentrations of 100 and 150 ug/ml (p < 0.05). The % viability of all concentrations used in the comet assay was greater than 80%. The % Tail DNA was significantly elevated compared to control for Degussa P25 AEROXIDE®Yi02at 100 ug/ml (3.57 ± 0.26% vs, 8.97 ± 0.33%, p < 0.05) after 24 hr treatment. The range of average sizes ofparticles in suspension were significantly larger than the manufacturer's listed size due to substantial agglomeration in the liquid phase (in KGM with 0.1% BSA-Degussa P25 AEROXIDE® Ti02: 531.3 -2089 nm, Alfa Aesar Ti02: 1081 -2189 nm). The results suggest that both Degussa P25 AEROXIDE® Ti02 and Alfa Aesar Ti02 (32 nm) caused oxidative damage to DNA. Additionally, the results indicate that Degussa P25 AEROXIDE® Ti02 may be genotoxic at concentrations of 100 ug/ml and higher, potentially due to free radical formation and oxidative stress mechanisms. [Abstract does not necessarily reflect the policies ofthe U.S. EPA.]