Efeitos dos nanomateriais Óxido de Grafeno e Óxido de Grafeno Reduzido sobre a linhagem celular de fígado de Danio rerio, ZFL

Abstract

Graphene nanomaterial and its variations such as graphene oxide (GO, graphene oxide) and reduced graphene oxide (rGO, reduced graphene oxide) have been widely studied and can be used in several areas, including bacterial inhibition, drug administration (drug delivery), photothermal therapy and bioremediation of aquatic environments, among other applications. Thus, aquatic environments and their compartments will be fatally affected by these nanomaterials, representing high risks for aquatic biota, as well as for human health. In these environments, GO remains stable for a long time and rGO, which is unstable when suspended in ultrapure water, becomes more stable in the presence of natural organic matter (NOM), being more stable than GO in these conditions. In addition, recent studies have shown that GO can be reduced to rGO by exposure to sunlight and bacterial degradation, as well as by the presence of metals such as aluminum (Al) and iron (Fe) and by sulfur-based inorganic reducers. The response of aquatic organisms, resulting from exposure to GO and rGO, is still poorly understood. In the present study, eight concentrations of the nanomaterials GO and rGO were tested in zebrafish liver cells (ZFL) on a scale of 0.001 to 100 μg mL-1, with exposures of 24 and 72 hours. The absorption of GO and rGO cells by ZFL, the production of reactive oxygen species (ROS), cell viability and death, as well as catalase activity (CAT) and S-transferase glutathione (GST) enzymes, as well as non-enzymatic antioxidant glutathione (GSH), were investigated. Lipid peroxidation and total antioxidant capacity were also investigated. GO and rGO showed lower absorption of proteins on their surface and GO adsorption more proteins than rGO. rGO nanosheets are smaller than GO nanosheets, and their hydrophobic characteristic favors their interaction with the cell membrane and, consequently, their entry into cells. Exposure to rGO generated higher ROS production than GO and caused more damage, evidencing greater toxicity of rGO. ZFL cells were able to combat the effects of GO by showing recovery after 72 hours of exposure, while exposure to rGO stopped cell replication at high concentrations. The exposure to low concentrations of rGO caused oxidative stress, loss of antioxidant capacity, and genotoxic damage. Exposure to rGO was harmful to ZFL cells within 24 hours and 72 hours of exposure.