Abstract
Few-layer graphene (FLG) has garnered much interest owing to applications in hydrogen storage and reinforced nanocomposites. Consequently, these engineered nanomaterials (ENMs) are in high demand, increasing occupational exposure. This investigation seeks to assess the inhalation hazard of industrially relevant FLG engineered with: (i) no surface functional groups (neutral), (ii) amine, and (iii) carboxyl group functionalization. A monoculture of human lung epithelial (16HBE14o- ) cells is exposed to each material for 24-h, followed by cytotoxicity and genotoxicity evaluation using relative population doubling (RPD) and the cytokinesis-blocked micronucleus (CBMN) assay, respectively. Neutral-FLG induces the greatest (two-fold) significant increase (p< 0.05) in micronuclei, whereas carboxyl-FLG does not induce significant (p< 0.05) genotoxicity. These findings correlate to significant (p< 0.05) concentration-dependent increases in interleukin (IL)-8, depletion of intracellular glutathione (rGSH) and a depletion in mitochondrial ATP production. Uptake of FLG is evaluated by transmission electron microscopy, whereby FLG particles are observed within membrane-bound vesicles in the form of large agglomerates (>1 µm diameter). The findings of the present study have demonstrated the capability of neutral-FLG and amine-FLG to induce genotoxicity in 16HBE14o- cells through primary indirect mechanisms, suggesting a possible role for carboxyl groups in scavenging radicals produced via oxidative stress.
Highlights
Few-layer graphene (FLG) has garnered much interest owing to applications in material containing particles, in an unbound state or as an aggregate or as an hydrogen storage and reinforced nanocomposites
The hydrodynamic diameters of FLG particles were observed to be larger when dispersed in 10% supplemented culture media as opposed to double-distilled water where the additional amine and carboxyl groups appeared to act as surfactants lowering the hydrodynamic diameter when compared to neutral-FLG
The effect of amine functionalization in the present study gave rise to an unexpected effect, that being to raise the zeta potential to a greater value than the carboxyl groups. This could be the result of an undesired oxygen-related functional group which may be contributing to the net negative zeta potential, given the oxygen content of amine-FLG was greater than carboxyl-FLG
Summary
Few-layer graphene (FLG) has garnered much interest owing to applications in material containing particles, in an unbound state or as an aggregate or as an hydrogen storage and reinforced nanocomposites These engiagglomerate and where, for 50% or more neered nanomaterials (ENMs) are in high demand, increasing occupational exposure. Neutral-FLG induces the greatest (two-fold) significant increase (p < 0.05) in micronuclei, whereas carboxyl-FLG does not induce significant (p < 0.05) genotoxicity These findings correlate to significant (p < 0.05) concentrationally relevant ways, largely due to their increased surface area to volume ratio.[3,4] Naturally, this demands interest where human health and environmental exposure are concerned given that ENMs possess unique properties which dependent increases in interleukin (IL)-8, depletion of intracellular glutathione potentially make them toxic.[5].
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