Xue-Ling Chang

Bioaccumulation and Toxicity of 13C-Skeleton Labeled Graphene Oxide in Wheat

Graphene nanomaterials have many diverse applications, but are considered to be emerging environmental pollutants. Thus, their potential environmental risks and biosafety are receiving increased attention. Bioaccumulation and toxicity evaluations in plants are essential for biosafety assessment. In this study, 13C-stable isotope labeling of the carbon skeleton of graphene oxide (GO) was applied to investigate the bioaccumulation and toxicity of GO in wheat. Bioaccumulation of GO was accurately quantified according to the 13C/12C ratio. Wheat seedlings were exposed to 13C-labeled GO at 1.0 mg/mL in nutrient solution for 15 d. 13C-GO accumulated predominantly in the root with a content of 112 μg/g at day 15, hindered the development and growth of wheat plants, disrupted root structure and cellular ultrastructure, and promoted oxidative stress. The GO that accumulated in the root showed extremely limited translocation to the stem and leaves. During the experimental period, GO was excreted slowly from the root. GO inhibited the germination of wheat seeds at high concentrations (≥0.4 mg/mL). The mechanism of GO toxicity to wheat may be associated with oxidative stress induced by GO bioaccumulation, reflected by the changes of malondialdehyde concentration, catalase activity, and peroxidase activity. The results demonstrate that 13C labeling is a promising method to investigate environmental impacts and fates of carbon nanomaterials in biological systems.

Surface modification-mediated biodistribution of 13C-fullerene C60 in vivo

BackgroundFunctionalization is believed to have a considerable impact on the biodistribution of fullerene in vivo. However, a direct comparison of differently functionalized fullerenes is required to prove the hypothesis. The purpose of this study was to investigate the influences of surface modification on the biodistribution of fullerene following its exposure via several routs of administration.Methods13C skeleton-labeled fullerene C60 (13C-C60) was functionalized with carboxyl groups (13C-C60-COOH) or hydroxyl groups (13C-C60-OH). Male ICR mice (~25 g) were exposed to a single dose of 400 μg of 13C-C60-COOH or 13C-C60-OH in 200 μL of aqueous 0.9% NaCl solution by three different exposure pathways, including tail vein injection, gavage and intraperitoneal exposure. Tissue samples, including blood, heart, liver, spleen, stomach, kidneys, lungs, brain, large intestine, small intestine, muscle, bone and skin were subsequently collected, dissected, homogenized, lyophilized, and analyzed by isotope ratio mass spectrometry.ResultsThe liver, bone, muscle and skin were found to be the major target organs for C60-COOH and C60-OH after their intravenous injection, whereas unmodified C60 was mainly found in the liver, spleen and lung. The total uptakes in liver and spleen followed the order: C60 > > C60-COOH > C60-OH. The distribution rate over 24 h followed the order: C60 > C60-OH > C60-COOH. C60-COOH and C60-OH were both cleared from the body at 7 d post exposure. C60-COOH was absorbed in the gastrointestinal tract following gavage exposure and distributed into the heart, liver, spleen, stomach, lungs, intestine and bone tissues. The translocation of C60-OH was more widespread than that of C60-COOH after intraperitoneal injection.ConclusionsThe surface modification of fullerene C60 led to a decreased in its accumulation level and distribution rate, as well as altering its target organs. These results therefore demonstrate that the chemical functionalization of fullerene had a significant impact on its translocation and biodistribution properties. Further surface modifications could therefore be used to reduce the toxicity of C60 and improve its biocompatibility, which would be beneficial for biomedical applications.

Bioaccumulation of 13C-fullerenol nanomaterials in wheat

Fullerenol, an important water-soluble derivative of fullerene carbon nanomaterial, has been increasingly used in medicine and industry. The presence and release of carbon nanoparticles into the environment have raised concerns over potential impacts on human health and the environment. In this study, the bioaccumulation of fullerenol nanoparticles in wheat was investigated using 13C-labelling techniques. The dose and time-dependent bioaccumulation of fullerenol in wheat was observed, and most fullerenol (about 85.68–263.86% ID per g, percentage of dose per gram tissue) was found in roots. With prolonged culture times, the seedlings treated with relatively low concentrations of fullerenol nanoparticles (2.5 μg mL−1) showed significant increases in 13C content in roots, while 10.0 μg mL−1 fullerenol appeared to suppress this accumulation. Only very limited amounts (<4.13% ID per g) of fullerenol nanoparticles were translocated from roots to stems and leaves. The presence of fullerenol nanoparticles was confirmed by scanning electron microscopy, and small particles were found in the vascular cylinder of wheat roots. During the incubations with fullerenol nanoparticles at all test concentrations, the biomass gain of stems and leaves was unaffected, while root elongation was promoted. Fullerenol also improved the synthesis of chlorophyll in wheat during the 7 d observation period.

Graphene/polyester staple composite for the removal of oils and organic solvents

Spongy graphene has been widely applied in oil removal. However, spongy graphene is hardly applicable for crude oil removal, because the complexity and high viscosity of crude oil. Herein, we reported that graphene/polyester staple composite (GPSC) could be used for the removal of oils and organic solvents, in particular crude oil. Graphene oxide was in situ reduced in the presence of polyester staple by hydrazine hydrate to form GPSC. GPSC efficiently adsorbed oils and organic solvents with high adsorption capacities. Demonstrations of treating pure oils and those in simulated sea water by GPSC were successfully performed. Due to the loose structure, GPSC adsorbed crude oil quickly with an adsorption capacity of 52 g g−1. During the regeneration, the adsorption capacity of GPSC retained around 78% of the initial capacity up to 9 cycles. The implication to the applications of GPSC in water remediation is discussed.

Toxicity of graphene oxide to naked oats (Avena sativa L.) in hydroponic and soil cultures

Graphene nanomaterials are emerging environmental pollutants and their toxicity to plants requires careful investigation in environmental matrixes. Actually, the transportation of graphene in hydroponic systems is completely different to that in soil, which might affect the interaction between graphene and plants. In this study, we compared the toxicity of graphene oxide (GO) to naked oats (Avena sativa L.) in hydroponic and soil cultures. Serious toxicity of GO was only observed in hydroponic culture. GO induced the inhibition of biomass gain, seedling length and photosynthesis of naked oats. The root structure was disturbed by GO and oxidative stress was aroused in the root. In contrast, the soil (vermiculite) interacted strongly with GO and restricted the transportation of GO in soil. This reduced the contact between GO and the roots and largely alleviated its toxicity. Our results collectively suggested that environmental biosafety evaluation should consider the impact of environmental behaviors of nanomaterials to better reflect the real bioeffect of nanomaterials.

Uptake and Transfer of 13C-Fullerenols from Scenedesmus obliquus to Daphnia magna in Aquatic Environment

Fullerenol, a water-soluble polyhydroxylated fullerene nanomaterial, enters aquatic organisms and ecosystems through different ingestion exposures and may pose environmental risks. The study of their uptake routes and transfer in aquatic systems is scarce. Herein, we quantitatively investigated the aquatic uptake and transfer of 13C-fullerenols from Scenedesmus obliquus to Daphnia magna using 13C-skeleton-labeling techniques. The bioaccumulation and depuration of fullerenol in Daphnia magna increased with exposure doses and time, reaching steady state within 16 h in aqueous and feeding-affected aqueous routes. The capacity of Daphnia magna to ingest fullerenol via the aqueous route was much higher than that via the dietary route. From the aqueous to feeding-affected aqueous, the kinetic analysis demonstrated the bioaccumulation factors decreases, which revealed that algae suppressed Daphnia magna uptake of fullerenols. The aqueous route was the primary fullerenols ingestion pathway for Daphnia magna. Kinetic analysis of the accumulation and transfer in Daphnia magna via the dietary route indicated low transfer efficiency of fullerenol along the Scenedesmus obliquus-Daphnia magna food chain. Using stable isotope labeling techniques, these quantitative data revealed that carbon nanomaterials underwent complex aquatic accumulation and transfer from primary producers to secondary consumers and algae inhibited their transfer in food chains.

Erratum to: Surface modification-mediated biodistribution of 13C-fullerene C60 in vivo

Author details Northwest University, Xi’an 710069, P. R. China. CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P. R. China. College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041, P. R. China. Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, P.R. China.