Influence of functional groups on toxicity of carbon nanomaterials

Yongchun Liu,Haotian Jiang,Hong He,Yanli Ge,Sijin Liu,Bo Zhang,Lian Wang,Chunmei Liu

doi:10.5194/acp-19-8175-2019

Abstract

Abstract. It has been recognized that carbon nanomaterials and soot particles are toxic for human health, but the influence of functionalization on their toxicity as well as the evolution of the toxicity of carbon nanomaterials due to chemical aging in the atmosphere is still controversial. In the current study, the oxidation potential measured by dithiothreitol (DTT) decay rate and the cytotoxicity to murine macrophage cells of different functionalized carbon nanomaterials were investigated to understand the role of functionalization in their toxicities. The DTT decay rates of special black 4A (SB4A), graphene, graphene oxide, single-walled carbon nanotubes (SWCNTs), SWCNT-OH and SWCNT-COOH were 45.9±3.0, 58.5±6.6, 160.7±21.7, 38.9±8.9, 57.0±7.2 and 36.7±0.2 pmol min−1 µg−1, respectively. Epoxide was found to be mainly responsible for the highest DTT decay rate of graphene oxide compared to other carbon nanomaterials based on comprehensive characterizations. Both carboxylation and hydroxylation showed little influence on the oxidation potential of carbon nanomaterials, while epoxidation contributes to the enhancement of oxidation potential. All these carbon nanomaterials were toxic to the murine J774 cell line. However, oxidized carbon nanomaterials (graphene oxide, SWCNT-OH and SWCNT-COOH) showed weaker cytotoxicity to the J774 cell line compared to the corresponding control sample as far as the metabolic activity was considered and stronger cytotoxicity to the J774 cell line regarding the membrane integrity and DNA incorporation. These results imply that epoxidation might enhance the oxidation potential of carbon nanomaterials.

Highlights

Carbon nanomaterials are predominantly composed of carbon atoms, only one kind of element, but they have largely diverse structures characterized by different degrees of crystallinity and different macro- and micromorphology (Somiya, 2013)
Previous work has found that oxidation of carbon nanomaterials (SWCNT) by O3 or OH under atmosphere-related conditions has little influence on their oxidative potential or cytotoxicity carbonyls, carboxylic acids and esters were formed (Liu et al, 2015)
Some other studies observed that the oxidation process enhanced the oxidation potential (Li et al, 2015, 2013; Antinolo et al, 2015) as well as the cytotoxicity (Holder et al, 2012) of Carbon black (CB) and soot particles

Summary

Introduction

Carbon nanomaterials are predominantly composed of carbon atoms, only one kind of element, but they have largely diverse structures characterized by different degrees of crystallinity and different macro- and micromorphology (Somiya, 2013). Their basic structure is that of graphite with planes of honeycomb-structured carbon atoms. CB is a quasi-graphitic form of nearly pure elemental carbon (EC, consists of graphene layers) It is distinguished by its very low quantities of extractable organic compounds and total inorganics (Long et al, 2013) compared to soot or black carbon (BC) (Andreae and Gelencser, 2006).

Results

Discussion

Conclusion