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

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.

Applicability of OECD TG 201, 202, 203 for the aquatic toxicity testing and assessment of 2D Graphene material nanoforms to meet regulatory needs

“…Use of ultrasonication, and particularly probe sonication, may cause a significant change in material properties. For example, breaks in flakes have been evidenced after probe sonication (Baig et al, 2018) and strikingly different size distribution profiles were evidenced when using bath or probe sonicators to prepare graphene nanoribbon stock dispersions (Mullick Chowdhury et al, 2014) and after short and prolonged sonication times (30 min vs. 2.5 h) (Jiang et al, 2021). In fact, prolonged sonication times were used to achieve dispersions of materials with smaller sizes for comparative testing.…”

“…In fact, prolonged sonication times were used to achieve dispersions of materials with smaller sizes for comparative testing. These distinct dispersions, produced using prolonged sonication times, have shown different interactions with organisms including enhanced membrane penetration ability (Su et al, 2017), increased cytotoxicity to cells (yeast and lung epithelial cells) (Jiang et al, 2021), and increased fish embryo mortality (Mullick Chowdhury et al, 2014). Aggressive sonication techniques have also been shown to increase defects (detected according to increased ratios of the intensity of D-Raman peak and G-Raman peak (I D /I G ) of 1.3 to 2.3) (Mullick Chowdhury et al, 2014), and likely also contributes to an increased toxicity as evidenced in the case of graphene nanoribbons, which, due to their form, may prove particularly susceptible to material transformations under such conditions.…”

“…However, the complete chemical composition of the material must be considered and accounted for, including any residual impurities or byproducts from production processes. Toxicological effects have also been evidenced to vary as a function of these distinct properties or their alterations (Liu et al, 2012;Sydlik et al, 2015;Jiang et al, 2021;Lu et al, 2017;Chen et al, 2021). For example lateral sheet size seemed to influence adverse effects towards zebrafish embryos in a comparative study, with larger sheets (>200-600 nm) showing increased toxicity through physical interactions and smaller sheets (<200 nm) not showing any effects (Moreira et al, 2021).…”

“…These post-processing manipulations can also directly affect toxicity assessments. For example high-energy sonication of graphene material can create smaller fragments with increased toxicity (Mullick Chowdhury et al, 2014: Jiang et al, 2021, while the presence of irregular sharp edges can lead to direct cell membrane destruction (Li et al, 2013). Also any residual impurities could be released from the material through such post processing (Kalman et al, 2019).…”

Toxicogenomics and Molecular Markers in Pollution

“…To complete the Special Issue, Jiang et al [ 14 ] used an innovative approach in toxicogenomics to analyze graphene oxide (GO), an important graphene-based material used in nanotechnology. These authors performed a three-dimensional high-throughput toxicogenomic-based analysis (exposure time, specific biomarker and expression alteration magnitude) employing a GFP-fused yeast reporter library to rapidly and effectively assess GO toxicity.…”