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.
