OXIDATIVE STRESS AND INFLAMMATORY RESPONSE IN DERMAL TOXICITY OF SINGLE-WALLED CARBON NANOTUBES.
This study by researchers at PPRB/NIOSH, West Virginia University and the University of Pittsburgh demonstrated that MatTek’s EpiDermFT full-thickness in vitro 3-D human skin tissue equivalent can be used to measure the dermal toxicity of single-walled carbon nanotubes (SWCNT). Single-walled carbon nanotubes (SWCNT) represent a novel material with unique electronic and mechanical properties. The extremely small size (~1 nm diameter) renders their chemical and physical properties unique. A variety of different techniques are available for the production of single-walled carbon nanotubes; however, the most common is via the disproportionation of gaseous carbon molecules supported on catalytic iron particles (high-pressure CO conversion, HiPCO). The physical nature of single-walled carbon nanotubes may lead to dermal penetration following deposition on exposed skin. This dermal deposition provides a route of exposure which is important to consider when evaluating single-walled carbon nanotube toxicity. The dermal effects of single-walled carbon nanotubes are largely unknown. We hypothesize that single-walled carbon nanotubes may be toxic to the skin. We further hypothesize that single-walled carbon nanotube toxicity may be dependent upon the metal (particularly iron) content of single-walled carbon nanotubes via the metal’s ability to interact with the skin, initiate oxidative stress, and induce redox-sensitive transcription factors thereby affecting/leading to inflammation. To test this hypothesis, the effects of single-walled carbon nanotubes were assessed both in vitro and in vivo using EpiDerm-FT engineered skin, murine epidermal cells (JB6 P+), and immune-competent hairless SKH-1 mice. Engineered skin (EpiDerm-FT) exposed to single-walled carbon nanotubes showed increased epidermal thickness and accumulation and activation of dermal fibroblasts which resulted in increased collagen as well as release of pro-inflammatory cytokines. Exposure of JB6 P+ cells to unpurified single-walled carbon nanotubes (30% iron) resulted in the production of ESR detectable hydroxyl radicals and caused a significant dose-dependent activation of AP-1. No significant changes in AP-1 activation were detected when partially purified single-walled carbon nanotubes (0.23% iron) were introduced to the cells. However, NF(kappa)B was activated in a dose-dependent fashion by exposure to both unpurified and partially purified single-walled carbon nanotubes. Topical exposure of SKH-1 mice (5 days, with daily doses of 40ìg/mouse, 80ìg/mouse, or 160ìg/mouse) to unpurified single-walled carbon nanotubes caused oxidative stress, depletion of glutathione, oxidation of protein thiols and carbonyls, elevated myeloperoxidase activity, an increase of dermal cell numbers, and skin thickening resulting from the accumulation of polymorphonuclear leukocytes (PMNs) and mast cells. Altogether, these data indicated that topical exposure to unpurified single-walled carbon nanotubes induced free radical generation, oxidative stress, and inflammation, thus causing dermal toxicity.
Carbon nanotubes, Cytokine release, EFT-400, EpiDerm-FT, EpiDermFT, Hyperkeratosis, IFN-gamma, IL-10, IL-12, IL-6, IL12p70, MCP-1, Morphological changes, Nanotubes, Parakeratosis, SWCNT, Single-walled carbon nanotubes, TNF-alpha
Carbon nanotubes, Single-walled carbon nanotubes (SWCNT)
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