Graphene is a two-dimensional (on the order of one atom thick) nanomaterial composed of carbon, consisting of a single layer of densely packed carbon atoms. Its high mechanical strength and significant electrical and thermal properties make graphene well suited for many new applications in the fields of electronics, biological, chemical and magnetic sensors, photodetectors, and energy storage and generation.
Did you know?
Due to its potential applications, graphene production is expected to increase considerably in the coming years, but given its low market uptake and the limitations in analyzing its effects, there is currently still not much information available on the concentrations of graphene nanomaterials in ecosystems.
Now it has become known that, like a Trojan horse, graphene oxide can transport organic pollutants to fish under certain conditions. Scientists from the CBET research group at the University of the Basque Country (UPV/EHU) in Spain and the University of Bordeaux in France have demonstrated in a study that graphene oxide nanomaterials, alone and in combination with polycyclic aromatic hydrocarbons, are a potential source of toxicity to fish, but at concentrations above currently expected environmental levels. Under the conditions used in the research, high toxicity has not been detected, but alteration of some biomarkers has been observed.
Take into account
As a consequence of the surface characteristics of graphene, once in the aquatic environment, graphene could act as a carrier of organic pollutants, such as polycyclic aromatic hydrocarbons, for aquatic organisms. In this regard, the CBET (Cell Biology in Environmental Toxicology) research group has evaluated the ability of graphene oxide to sorb polycyclic aromatic hydrocarbons and the toxicity of graphene oxide alone and in combination with certain polycyclic aromatic hydrocarbons in zebrafish embryos and adults.
“The results have shown that graphene oxide can carry polycyclic aromatic hydrocarbons into the zebrafish (via a kind of Trojan horse effect) and produce sublethal damage. Under the conditions we used, the toxic effects have not been enormous, neither fish nor embryos have died, but in some biomarkers we have detected effects that warn us”, said Amaia Orbea, doctor of the CBET group of the UPV/EHU.
On the one hand, they have detected that malformations can occur in embryos at high concentrations, “which means that in longer exposures and at higher concentrations it is possible that non-viable animals may be born”, explains Orbea. On the other hand, this research has shown that “in the long term, in a three-week exposure, the enzyme acetylcholinesterase, which slows down nervous stimuli, was inhibited in all the treated fish, so despite not using very high concentrations, we have seen that as the exposure time increases, neurotoxic effects begin to appear,” the researcher pointed out.
Keep in mind
“We have used specific concentrations and time periods, but we do not know how these concentrations will evolve from now on in nature and their possible influence in relation to other pollutants. The results have shown us that the concentrations that may exist at this time in the environment are not very dangerous, but we must be careful: we do not know what effects these low concentrations may have in longer exposures. The results obtained are related to the conditions applied in our experiments. Normally we do not find graphene alone in the environment; along with graphene there are many other pollutants that also affect animals… We should consider them all at the same time,” he warns.
This study is part of the international co-supervised thesis of the PhD student Ignacio Martínez Álvarez. The research has been funded by the UPV/EHU, Amaia Orbea is the thesis director of the UPV/EHU and Hélène Budzinski the thesis director of the University of Bordeaux. The research has been carried out at the Department of Zoology and Animal Cell Biology and at the Center for Research in Experimental Marine Biology and Biotechnology (Plentzia Marine Station), in collaboration with Polymat.
Final note
The study is entitled “Uptake and effects of graphene oxide nanomaterials alone and in combination with polycyclic aromatic hydrocarbons in zebrafish”. It has been published in the academic journal Science of the Total Environment. (Source: UPV/EHU)