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ENHANCED TOXICITY OF CHARGED CARBON NANOTUBES AND ULTRAFINE CARBON BLACK PARTICLES
Citation:
GILMOUR, M. I., W. C. WILLIAMS, J. K. MCGEE, AND R. K. SAXENA. ENHANCED TOXICITY OF CHARGED CARBON NANOTUBES AND ULTRAFINE CARBON BLACK PARTICLES. Presented at Society of Toxicology Annual Meeting, Charlotte, NC, March 25 - 29, 2007.
Description:
Man-made carbonaceous nano-particles such as single and multi-walled carbon nano-tubes (CNT) and ultra-fine carbon black (UFCB) particles are finding increasing applications in industry, but their potential toxic effects is of concern. In aqueous media, these particles cluster in large aggregates and their interactions with lung cells is rather inefficient. Nonetheless, these particulates have a time and dose dependent toxic effect on lung epithelial cells in culture. Recently, a method to solubilize carbon nano-tubes by heating the nano-tubes in a microwave oven with a mixture of sulfuric and nitric acid under high pressure, was described in order to improve the dispersal property and utility of SWCNTs (Wang et al J Am Chem Soc 128, 95, 2006). By using this procedure we generated particles that dispersed much more efficiently in aqueous media because of the introduction of negatively charged sulfonate and carboxy groups on carbon atoms. Compared to control untreated preparations of nano-particles, acid functionalized carbon nano-tubes as well as ultrafine carbon black were significantly more toxic to LA4 lung epithelial cells in culture as measured by the reduction in cell viability. Microscopic examination showed increased uptake of acid functionalized nano particles (AFNP) by the epithelial cells and flow cytometric studies indicated a significant decrease in the proportion of LA4 cells in S phase of the cell cycle. Pretreatment with poly L-lysine, a polymer that is positively charged and hence could neutralize the negative charge on AFNPs, resulted in abrogation of the toxic effects of AFNPs. These results indicate that dispersability and charge are important criteria in determining the toxicity of nano-particles to lung epithelial cells. This abstract does not reflect EPA policy.