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Assessment of ecocorona acquired by Graphene Family Nanomaterials during exposure to biofilms and fate following uptake

Periodic Reporting for period 1 - ToxEcoGraphene (Assessment of ecocorona acquired by Graphene Family Nanomaterials during exposure to biofilms and fate following uptake)

Reporting period: 2018-05-01 to 2020-04-30

The increasing integration of high-performance advanced materials and nanotechnology in everyday life applications imposes a pressing need to shed light not only on the fundamental nanomaterial features and properties, but also on the environmental processes that will determine their distribution and fate in the environment. Graphene Family Nanomaterials (GFN) are undoubtedly some of the most promising nanomaterials developed to date, combining unique features and physicochemical properties that can be exploited in a plethora of applications. Given the serious concerns raised over the potential impact of GFN on the environment, and in order for GFN nanotechnology to develop in a sustainable manner, it is crucial to ensure that development of GFN takes place alongside research focused on its consequences for public health and potential environmental impacts. One major objective of the project was to develop, characterise and utilise GFN-oriented protocols and methods to facilitate investigation of fate and transport in natural complex media. Various physicochemical properties were studied, including the flake dimensions, particulate state, surface chemistry etc. Investigation of GFN fate in natural media has been conducted by focusing on the aggregation kinetics and stability of GFN in aquatic environments. The evaluation of GFN toxicity to biofilms was another objective, by focusing on hetero-aggregation and eco-corona growth on GFN surface and assessing changes in community structures as a function of exposure concentrations and durations. Aquatic systems include a complex heterogeneous plethora of several types of organic molecules, ranging from humic substances to polysaccharides and proteins, briefly described as natural organic matters. Thus, GFN environmental fate, including transport, stability, dissolution, bioavailability, and ecotoxicity is strongly depended on the interaction between them. Another main objective was the implementation of the main research conclusions in order to mitigate identified environmental impact and design-out potential hazards related to GFN technology and applications. Graphene family nanomaterials have a great potential to become a key solution for advanced composite materials with enhanced properties and applicability in a wide range of application sectors. Several crucial aspects related to the impact of GFN and nanomaterials in general need to be addressed through European Union policies and a coherent regulatory framework supported by effective standards.
The project’s main objective was to develop, characterise and utilise GFN-oriented protocols and methods to facilitate investigation of GFN fate and transport in natural complex media. GFN samples’ physicochemical properties were studied, including the particle/flake dimensions, particulate state, surface chemistry/surface functional groups, and surface charges/oxygen content. All these features can impact significantly the GFN toxicity when released to the environment. Investigation of GFN fate and natural media has been conducted by focusing on the aggregation kinetics and stability of GFN in aquatic environments. The main finding of these studies is that graphene oxide, exhibited enhanced stability in both synthetic and natural surface water for long-term period and this can be regarded as an evidence that graphene oxide can potentially be transported in aquatic systems for relatively long periods. Thus, when graphene oxide is released to the aquatic environment it will tend to accumulate and move through living organisms and thus it can potentially affect human health though the food chain. Based on the research findings, the formation of aggregates influenced highly the transport fate of GFN in aquatic environment and can therefore regulate its ecotoxicological effect. Another environmental factor that was also considered was the presence of natural organic matters. Surface shielding of GFN samples by humic substances can not only affect their transport characteristics, but at the same time can mitigate their oxidative stress and thus alter their ecotoxicological impact. The determination of the effect and the evaluation of GFN toxicity to biofilms was another objective, by focusing on environmental fate processes, mainly on hetero-aggregation and growth of the eco-corona on graphene’s surface and assessing changes in community structures as a function of exposure concentrations and durations. The results exhibited that the increase of protein concentration resulted in the increase of nanomaterials’ colloidal stability even for long-term studies. Thus, this is expected to play critical role in highly complex aquatic systems, and other protein-rich environments, and this can probably mean different transport fate and interaction with other contaminants leading to an enhanced ecotoxicity profile. Protein corona on the surface of nanomaterials can play a decisive role to their exposure behaviour and fate, and thus to their environmental impact. Moreover, the surface formed protein corona can modulate the formation of aggregates, and thus define their transport in aquatic systems. Research outcomes highlighted the critical effect of protein corona on the GFN samples dispersion stability, resulting in hindering of the formation of aggregates over various time intervals. Proteomics analysis provided evidence that the physicochemical features and morphological properties of GFN samples played an important role in the protein corona formation. Biofilms exhibit responsiveness to various external factors and stressors, and therefore biofilms can be utilized as model organisms and to gain insight into the toxicity mechanisms. Overall, the incubation of biofilms with GFN samples evidenced that the biofilm structure can be compromised in a concentration dependent manner, and differs according to nanomaterials structural features and stability/transport behaviour.
Graphene nanomaterials have a great potential to become a key solution for advanced composite materials with enhanced properties and applicability in a wide range of industrial sectors and commercial products. The project aimed to address many theoretical and experimental issues related to the research on the nanoecotoxicological impacts of GFN and tried to place emphasis on environmentally relevant species and conditions The project’s impact involves the importance of the environmental transformation processes in order to assess the risks. By conducting interdisciplinary research simultaneously the project offered novel insights and advanced the state-of-the art in the field of nanoecotoxicology of GFN. This was achieved through the adoption of a theoretical and analytical approach covering aspects of materials science, nanotechnology, ecotoxicity. The project outcomes have the potential to advance our understanding in GFN ecotoxicological impacts. Overall, the project aimed to provide to EU nanotechnology-related industry and other stakeholders with valuable knowledge and datasets to support related regulations. Also, the protein-corona investigation can provide important hints in the nanomedicine applications of GFN. Knowledge obtained in this project, can lead to safe-by-design tailoring of the physicochemical properties of GFN and can therefore increase their applications potentials and reduce environmental impact.
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