Natural Nanocolloids Mediate the Phytotoxicity of Graphene Oxide

Abstract

Nanocolloids (Ncs) are ubiquitous in natural surface waters. However, the effects of Ncs on the fate and ecotoxicity of graphene oxide (GO, a popular engineered nanomaterial (ENM)) remain largely unknown. Ncs exhibit strong adsorption affinity (K L = 1.93 L/mg) and high adsorption capacity (176.2 mg/g) for GO. After Ncs hybridization, GO nanosheets became scrolls, and the aggregation rate of GO decreased. The influence of humic acid and Ncs on GO toxicity was compared. Humic acid mitigated the phytotoxicity of GO. However, GO and GO-Ncs were found to have an envelopment effect on algal cells, and both could enter algal cells. GO-Ncs induced higher reactive oxygen species (ROS) generation, stronger DNA damage and plasmolysis, and more obvious inhibition of photosynthesis compared to GO. Proteomic analysis revealed that photosystem I-and II-related proteins (e.g., E1ZQR2 and E1ZPG5) were regulated more significantly in the GO-Ncs groups than in the GO groups. A combined proteomic and metabolomic analysis showed that inhibition of carbohydrate, fatty acid, and amino acid metabolism contributed to ROS generation. Given the high concentrations and activity of Ncs, the above results highlight the need for reconsideration of the Ncs-mediated environmental behaviors and risks of ENMs and other pollutants.

Mutual impacts and interactions of antibiotic resistance genes, microcystin synthetase genes, graphene oxide, and Microcystis aeruginosa in synthetic wastewater

“…Notably, in 0.01 mg/L GO-exposure group, an increase in amino acid metabolism including increase in L-threonine, L-valine, L-alanine, and L-proline, was observed. These findings are in accordance with previous studies where an increase in amino acid turnover in stimulated algal cells by low concentration of GO was reported (Ouyang et al 2020). The other important metabolic pathway found to be altered in M. aeruginosa in 0.01 GO-exposure group was nucleotide metabolism, including increase of uracil and hypoxanthine.…”

Humic Substances as Microalgal Biostimulants—Implications for Microalgal Biotechnology

“…Humic acids reduce the toxicity of graphene family materials (GFMs) toward microalgae, Tetradesmus obliquus (synonym used Scenedesmus obliquus ) [ 100 ], and Chlorella pyrenoidosa [ 92 ]. The toxicity mechanism of GFMs is the membrane damage associated with oxidative stress [ 101 ]. Humic acids interact with GFMs and decrease GFM aggregation and adhesion to the microalgae cell membrane due to steric hindrance [ 92 ].…”

Direct and Indirect Genotoxicity of Graphene Family Nanomaterials on DNA—A Review

“…ROS induced by GO seemed to be the main mechanism leading to human lung fibroblast (HLF) cells of genotoxicity [86]. Natural nanocolloids (Ncs) can mediate the phytotoxicity of GO such that GO-Ncs induced stronger ROS production and DNA damage compared with GO alone [87]. The mitochondrial oxidative stress induced by GQDs in microglia can cause ferroptosis.…”

“…The most commonly used detection technique includes direct observation of localization of GFNs in organisms and cells by transmission electron microscopy (TEM) [88]. The hyperspectral imaging is also used to visualize cellular interactions with NPs [134], such as cellular uptake and binding of GFNs [87]. The label-based approaches to image GFNs exist in cells by confocal and fluorescence microscopy, reflection-based imaging, and flow cytometry.…”

“…The label-based approaches to image GFNs exist in cells by confocal and fluorescence microscopy, reflection-based imaging, and flow cytometry. Additionally, scanning electron microscopy (SEM) can be used to detect the attachment of GFNs in the surface zone of cells [52,87]. Raman spectroscopy and atomic force microscopy (AFM) were used to evaluate nuclear area changes and the disruption of DNA chains impacted by GQDs, respectively [69].…”