Dependence of Graphene Oxide (GO) Toxicity on Oxidation Level, Elemental Composition, and Size.

Tao Jiang,Carlo Alberto Amadei,Yishan Lin,Jiaqi Lan,April Z Gu,Chad D Vecitis,Na Gou,Sheikh Mokhlesur Rahman

doi:10.3390/ijms221910578

Abstract

The mass production of graphene oxide (GO) unavoidably elevates the chance of human exposure, as well as the possibility of release into the environment with high stability, raising public concern as to its potential toxicological risks and the implications for humans and ecosystems. Therefore, a thorough assessment of GO toxicity, including its potential reliance on key physicochemical factors, which is lacking in the literature, is of high significance and importance. In this study, GO toxicity, and its dependence on oxidation level, elemental composition, and size, were comprehensively assessed. A newly established quantitative toxicogenomic-based toxicity testing approach, combined with conventional phenotypic bioassays, were employed. The toxicogenomic assay utilized a GFP-fused yeast reporter library covering key cellular toxicity pathways. The results reveal that, indeed, the elemental composition and size do exert impacts on GO toxicity, while the oxidation level exhibits no significant effects. The UV-treated GO, with significantly higher carbon-carbon groups and carboxyl groups, showed a higher toxicity level, especially in the protein and chemical stress categories. With the decrease in size, the toxicity level of the sonicated GOs tended to increase. It is proposed that the covering and subsequent internalization of GO sheets might be the main mode of action in yeast cells.

Highlights

Graphene-based materials (GNMs) possess outstanding electronic, thermal, and mechanical traits, making them one of the most promising engineered carbon-based nanomaterials (CNMs) [1,2,3]
The gene ontology analysis confirmed that the DNA metabolic process was overrepresented, and various proteins in all the DNA repair pathways were involved, such as PHR1 related to direct reversal repair (DRR), OGG1 related to base excision repair (BER), as well as XRS2 and MRE11 related to double strand break (DSB)
The toxicity of graphene oxides (GOs), and its dependence on oxidation level, elemental composition, and size, were comprehensively and systematically evaluated with five Graphene oxide (GO), i.e., untreated control GO, UV-treated GO with different elemental compositions, thermally reduced GO with a lower oxidation level, and two sonicated

Summary

Introduction

Graphene-based materials (GNMs) possess outstanding electronic, thermal, and mechanical traits, making them one of the most promising engineered carbon-based nanomaterials (CNMs) [1,2,3]. GO is a form of graphene with chemical modification and a high oxidation degree, which possesses colloidal stability in biologic media and carries a negative surface charge with the epoxide and hydroxyl functional group [5]. The application of GO would generate remarkable economic advantages, the mass production of GNMs unavoidably elevates the possibility of releasing them into the environment, raising public concern about their potential toxicological effects and the risks to humans and ecosystems. These 2-D nanomaterials tend to dissolve in aquatic environments over time and are highly stable [16]. The assessment of GO toxicity is of great importance for environmental and human health

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Discussion

Conclusion