Distribution,Toxicity And Environmental Ecological Effects Of Graphene Nanomaterials In Plants

Graphene and its derivatives have attracted extensive attention due to their unique structure,properties and their outstanding performance.Graphene nanomaterials have many applications in diverse areas,which stimulate the large-scale production of graphene in industry.The production and diversity of graphene products are increasing year by year.Therefore,the potential biosafety of graphene products is continuously increasing and now graphene is considered as potential environmental pollutant.To evaluate the biosafety of graphene,the very first issue is to quantify it in environmental biosystems,which is essential information for evaluating the environmental behavior and bio-effects of graphene.Isotope ratio mass spectrometry?IRMS?is a technique that analyzes the ¹³C/¹²C ratio changes to quantify the stable isotope in samples.Here,stable isotope ¹³C labeling was adopted to successfully resolve the quantification of graphene in plants.The accumulation and migration of graphene in plants were firstly quantified.The corresponding toxicity evaluations were performed.First,graphene oxide?GO?was choosen as the representative graphene material.¹³C skeleton labeled GO was prepared,and the migration and distribution of GO in wheat were quantified.Under the supervising of quantification data,the bio-effects of GO to wheat were studied.Second,the the migration and distribution of GO and reduced GO?RGO?,which were different in oxygen contents,were compared in pea.The influence of the photosynthesis and toxicity were evaluated on pea.Third,the toxicity of GO to naked oat was investigated under different cultivation systems.The difference was explained by the interaction between GO and culture media.According to the aforementioned experiments,the main results are listed as follows:1.Accumulation and bio-effects of ¹³C-GO in wheat:¹³C-GO accumulated predominantly in the root with a content of 112?g/g at day 15,hindered root development,decreased seedling length and biomass,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.2.Differences of GO and RGO in the bioaccumulation and bio-effects in pea:By using ¹³C-skeleton labeling quantification method,RGO was found to enter the leaves much easier than GO.At day 20,the ¹³C-RGO reached 1404?g/g in leaves,inhibited the photosynthesis parameters,and aroused structural changes there.The toxicological mechanism was related to oxidative stress.Similar the results in wheat,GO majorly accumulated in root and showed low effects to leaves.The main toxicity was observed in root,including the structural changes and oxidative stress.The overall toxicity of GO was higher than RGO.3.Influence of plant cultivation method on the bio-effects of GO:Serious toxicity of GO was only observed in hydroponic culture.GO induced the inhibition of biomass gain,seedling length and phtosynthesis to naked oats.The root structure was disturbed by GO and the oxidative stress was aroused in root.In contrast,soil?vermiculite?interacted strongly with GO and restricted the transportation of GO in soil.This might reduce the contact of GO with roots and largely alleviated its toxicity.