Abstract
The plate-like graphene shells (GS) produced by an original methane pyrolysis method and their derivatives graphene oxide (GO) and graphene oxide paper (GO-P) were evaluated with luminescent Escherichia coli biotests and additional bacterial-based assays which together revealed the graphene-family nanomaterials' toxicity and bioactivity mechanisms. Bioluminescence inhibition assay, fluorescent two-component staining to evaluate cell membrane permeability, and atomic force microscopy data showed GO expressed bioactivity in aqueous suspension, whereas GS suspensions and the GO-P surface were assessed as nontoxic materials. The mechanism of toxicity of GO was shown not to be associated with oxidative stress in the targeted soxS::lux and katG::lux reporter cells; also, GO did not lead to significant mechanical disruption of treated bacteria with the release of intracellular DNA contents into the environment. The well-coordinated time- and dose-dependent surface charge neutralization and transport and energetic disorders in the Escherichia coli cells suggest direct membrane interaction, internalization, and perturbation (i.e., “membrane stress”) as a clue to graphene oxide's mechanism of toxicity.
Highlights
Graphene is a two-dimensional one-atom thick layer of carbon packed into a honeycomb-like structure [1, 2]
In this work we studied graphene shells synthesized using an original methane pyrolysis method [28], a graphene oxide derivative [29], and graphene oxide paper in several Escherichia coli biotests sufficient to reveal the graphene-family nanomaterials (GFNs)’ toxicity and bioactivity mechanisms
Combining a bioluminescence inhibition assay and twocomponent fluorescence in order to evaluate cell membrane permeability with atomic force microscopy, there was an absence of detectable bioactivity for graphene shells (GS)
Summary
Graphene is a two-dimensional one-atom thick layer of carbon packed into a honeycomb-like structure [1, 2]. The technology of graphene and its derivatives have been developing actively [6]. The growing interest in graphene-family nanomaterials (GFNs) is driving the study of their biological activity as well. It is necessary to evaluate environmental risks of graphene-containing technological objects to biological systems [10], as it is for other carbon-based nanomaterials [11], in particular, fullerenes [12] and nanotubes [13]. Increasing information about graphene toxicity shows that its number of layers, lateral size, stiffness, hydrophobicity, surface functionalization, and dose are important [1, 14,15,16,17]. The toxicity and biocompatibility of GFNs are still debated [18]
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