Influence of functional groups on toxicity of carbon nanomaterials

Abstract

Abstract. It has been recognized that carbon nanomaterials and soot particles are\ntoxic for human health, but the influence\nof functionalization on their toxicity as well as the evolution of the\ntoxicity of carbon nanomaterials due to chemical aging in the atmosphere is still controversial. In\nthe current study, the oxidation potential measured by dithiothreitol (DTT)\ndecay rate and the cytotoxicity to murine macrophage cells of different\nfunctionalized carbon nanomaterials were investigated to understand the role\nof functionalization in their toxicities. The DTT decay rates of special\nblack 4A (SB4A), graphene, graphene oxide, single-walled carbon nanotubes\n(SWCNTs), SWCNT-OH and SWCNT-COOH were 45.9±3.0 , 58.5±6.6 ,\n 160.7±21.7 , 38.9±8.9 , 57.0±7.2 and 36.7±0.2 \u2009pmol\u2009min −1 µ g −1 , respectively. Epoxide was found to be mainly\nresponsible for the highest DTT decay rate of graphene oxide compared to\nother carbon nanomaterials based on comprehensive characterizations. Both\ncarboxylation and hydroxylation showed little influence on the oxidation\npotential of carbon nanomaterials, while epoxidation contributes to the\nenhancement of oxidation potential. All these carbon nanomaterials were\ntoxic to the murine J774 cell line. However, oxidized carbon nanomaterials\n(graphene oxide, SWCNT-OH and SWCNT-COOH) showed weaker cytotoxicity to the J774\ncell line compared to the corresponding control sample as far as the\nmetabolic activity was considered and stronger cytotoxicity to the J774 cell\nline regarding the membrane integrity and DNA incorporation. These\nresults imply that epoxidation might enhance the oxidation potential of\ncarbon nanomaterials.