Mechanistic understanding toward the toxicity of graphene-family materials to freshwater algae

Abstract

We systematically investigated the toxicity mechanism of three graphene-family materials (GFMs), graphene oxide (GO), reduced graphene oxide (rGO) and multi-layer graphene (MG), to algae (Chlorella pyrenoidosa). GFMs exhibited much higher toxicity than other carbon materials (carbon nanotube and graphite), with the 96 h median effective concentration (EC) values of 37.3 (GO), 34.0 (rGO), and 62.2 (MG) mg/L. Shading effect contributed approximately 16.4% of growth inhibition by GO due to its higher dispersibility and transformation while the other GFMs did not show any shading effect. Hydrophobic rGO and MG more readily heteroagglomerated with algae than GO, thus likely leading to more direct contacts with algae. Flow cytometry results showed significant decrease of membrane integrity after GFM exposure, and rGO caused the highest membrane damage, which was confirmed by the increased DNA and K efflux. The observed membrane damage was caused by a combination of oxidative stress and physical penetration/extraction. Moreover, all the three GFMs could adsorb macronutrients (N, P, Mg, and Ca) from the algal medium, thus leading to nutrient depletion-induced indirect toxicity. GO showed the highest nutrient depletion (53% of total toxicity) due to its abundant functional groups. The information provided in this work will be useful for understanding toxicity mechanism and environmental risk of different GFMs in aquatic environments.

Toxicity of ZnO/TiO2‐conjugated carbon‐based nanohybrids on the coastal marine alga Thalassiosira pseudonana

“…A similar observation when there was more toxicity of GO on algal cells compared to CNT was observed in a recent study by Zhao et al, possibly due to GO's hydrophilic surface and strong electrostatic repulsion between GO sheets. Lv et al reported that GO could be more toxic than other carbon nanomaterials due to its enhanced dispersibility and high hydrophilicity, whereas CNTs are hydrophobic nanomaterials that are likely to form more aggregates.…”

Graphene-Based Nanomaterials Toxicity in Fish

“…Because of the release of considerable amounts nanoparticles into the environment almost every day, and for the ERC guidelines, investigations on the effect of GPN on aquatic organisms are critical. Some studies have found that GPN exhibited high toxicity to marine and freshwater algae, damaged organelles, enhanced ROS generation, induced nutrition depletion, and reduced photosynthetic pigment concentration (Hazeem et al 2016; Zhao et al 2017; De Marchi et al, 2018). We have also documented from the published literature included in this review that GPN was able to penetrate the chorion (both zebrafish and Japanese medaka) and reach the embryonic body in fish during development and causing DNA damage.…”

Influence of reduced graphene oxide on the growth, structure and decomposition activity of white-rot fungus Phanerochaete chrysosporium

“…16 Zhao et al reported that RGO was more toxic than GO to freshwater algae because the hydrophobic RGO more readily heteroagglomerated with algae. 17 RGO was reported to reduce the hatching rate of zebrash embryos and the length of larvae, while carbon nanotubes (CNTs) and GO had limited impact.…”