Comparative cytotoxicity assessments of some manufactured and anthropogenic nanoparticulate materials
Due to increasing diversity of newly engineered nanoparticles, it is important to consider the hazards of these materials. Very little is known regarding the potential toxicity of relatively new nanomaterials. However, beginning with several historical accounts of nanomaterials applications---chrysotile asbestos and silver---it was assumed that these examples would provide some awareness and guidelines for future nanomaterial and nanotechnology applications, especially health effects. In this study in vitro assays were performed on a murine alveolar macrophage cell line (RAW 264.7), human alveolar macrophage cell line (THB-1), and human epithelial lung cell line (A549) to assess the comparative cytotoxicity of a wide range of manufactured (Ag, TiO2, Fe2O3, Al2O3, ZrO2, black carbon, two different types of multiwall structures and chrysotile asbestos as the toxicity standard) and anthropogenic nanoparticulates. There are several parameters of nanoparticulates that are considered to trigger an inflammatory response (particularly respiratory) or cause toxicity. These parameters include: particle size, shape, specific surface area, transition metals in particulates, and organic compounds. Therefore, a wide variety of manufactured and anthropogenic nanoparticulates having different morphologies, sizes, specific surface area and chemistries as noted were tested. To determine the nanoparticulates' size and morphology, they were characterized by transmission electron microscopy, where it was observed that the commercial multiwall carbon nanotube aggregate had an identical morphology to chrysotile asbestos and combustion-formed carbon nanotubes, i.e.; those that form from natural gas combustion. Light optical microscopy was used to determine cell morphology upon exposure to nanoparticulates as an indication of cell death. Also, the polycyclic aromatic hydrocarbon (PAH) content of the collected nanoparticulates was analyzed and correlated with cytotoxic responses. For toxicity evaluation, cytokine production, mitochondrial function (MTT assay), reactive oxygen species generation (ROS), were assessed after 48 and 336 hours under control and exposed conditions. A simple, direct-contact assay was developed to evaluate the toxicity of anthropogenic particulate matter (PM), without removing it from high volume filter collections and exposing collected PM by direct contact with the human epithelial (A549) cells in culture. The cell viability data revealed that the manufactured nanomaterials exhibit cytotoxic response for the murine alveolar and human macrophage cell line, but in particular to the human epithelial cell line. Assay results for the direct-contact of filter-collected carbonaceous nanoparticulate, showed toxicity for all PM, but with various natural gas combustion PM being the most toxic. Light optical microscopy examination of affected human epithelial cells confirmed quantitative results. These nanoparticulate soots also produced the most reactive oxygen species (ROS) on the A549 cell culture as well as along with the Fe2O3, MWCNT-N, and black carbon (BC). Comparison of polycyclic aromatic hydrocarbon (PAH) content and concentration for the carbonaceous PM showed no PAH correlation with relative cell viability after 48 h. In addition, there was no correlation of cytotoxic response with specific surface area in the manufactured nanoparticulate materials. In conclusion, the manufactured as well as the anthropogenic nanomaterials were observed to generate large amounts of ROS and cytokines. This study suggests that the mechanism of toxicity is likely due to the generation of reactive oxygen species (ROS). Also, the comparative assessments presented, should be viewed as a precaution when considering the inhalation of the corresponding nanoparticulate materials in concentrations approaching those identified to be dangerous for recognized pathogens such as silica, black carbon, and asbestos. Humans should avoid breathing these nanoparticulate materials, although there are anthropogenic nanoparticulate materials such as MWCNT aggregates produced by natural gas stoves in homes which can provide low dose, long-term exposure prospects. Lastly, the implementation of nanomaterials or nanotechnology requires societal and ethical considerations as a principal part of design implementation, manufacturing, or life-cycle and re-cycle issues.
Soto, Karla Fabiola, "Comparative cytotoxicity assessments of some manufactured and anthropogenic nanoparticulate materials" (2007). ETD Collection for University of Texas, El Paso. AAI3262905.