<i>In vitro</i> cytotoxicity and induction of apoptosis by multiwalled carbon nanotubes in human peripheral lymphocytes: Correlation with physicochemical properties

Abstract

Multiwalled carbon nanotubes (MWCNTs) consist of more than 80% of the current nanomaterials’ applications worldwide. Despite their wide application, little information is known concerning their impact on human health. The current study aims to identify the in vitro effects of exposure of the human peripheral blood lymphocytes (PBL) to MWCNTs and the possible associations with their physiochemical properties. Two doses (50 and 500 µg/ml) of four different commercially available MWCNTs (obtained from Frascati Laboratory, Sigma Co., Sun Nanotech Co. and Shenzhen Co.) were used in this study. Cell viability and apoptotic activity were evaluated by trypan blue exclusion test and Annexin-V/PI staining in peripheral blood leukocytes (PBL). Physicochemical properties of the different MWCNTs were determined and correlated with the cytotoxicity results after exposure for 12 and 48 h. Results indicate that PBL exposed to MWCNTs showed decreased cell viability and increased apoptosis in a dose- and time-dependent manner. The Pearson’s correlation test showed a lack of relationship between diameter of nanoparticles and their pro-apoptotic activity (r²= 0.282), whereas significant correlations were found between pro-apoptotic activity and the presence of some metal contaminants such as nickel, cobalt and gold (r²= 0.919, 0.698 and 0.520, respectively). Our results therefore suggest that carbon nanotubes at high concentrations lowered cell viability in vitro and induced apoptosis in human cells in vitro. In addition, the results indicate that metal contaminants in carbon nanotubes may be causative of some of the adverse outcomes observed. Finally, our finding provides important information on the biohazard potential of some carbon nanotubes in humans.

Key words: Multiwalled, carbon, nanotubes, cytotoxicity, apoptosis, flow cytometry, viability,  lymphocytes.