Avaliação toxicogenética de pontos quânticos de grafeno (GQD) em modelos experimentais alternativos

Abstract

Nanomaterials are characterized by their nanometer scale size. They are created through natural events or man-made and are applied in several areas. Amidst them, carbon nanomaterials have interesting properties, such as their biocompatibility. Graphene quantum dots (GQD) is a carbonaceous nanomaterial it is remarkable for its possible suitability both in disease treatment and imagening. However, its presence in the environment demands an assessment of its possible adverse effects, especially on human health. To determine the safety of a drug, toxicological assessments are necessary, adopting alternative in vitro methodologies to reduce the use of animals in research. To further reduce the disparity in response of alternative and in vivo models, new protocols, such as three-dimensional culture of cell lines, are used. Cytotoxicity assays evaluates the potential of a substance of interest to induce cell death. While genotoxicity assays search for possible DNA damage, both as the induction of mutagenicity and aneugenic/clastogenic events. The aim of this work was to evaluate aspects of the toxicity of GQD, using alternative in vitro methodologies, to determine the safety of this nanomaterial. The Ames test was performed for the detection of mutagenicity. Strains TA97a, TA98, TA100, TA102, TA104 and TA1535 of Salmonella Typhimurium were exposed to different concentrations of GQD ranging from 1 to 1000 μg/plate in the presence or absence of exogenous metabolization. Mutagenicity was induced in TA97a without exogenous metabolism (S9 mix), but not in the presence. With exogenous metabolism, mutagenicity was observed only in TA102 strain with exogenous metabolization. Positive results in this test strain indicates involvement of reactive oxygen species in this event. For tests using cell culture, the 3T3BalbC and HepG2 strains were used. The WST-1 and LDH cell viability assays demonstrated that GQD decreases cell viability, especially of 3T3BalbC cells. However, when cells were cultivated in a tridimensional model culture, GQD’s cytotoxic effect was diminished in both cell lines. GQD also increases the frequency of micronuclei in 3T3BalbC cells and caused a cytostatic effect, with no significant impact on HepG2, comparably effect of the observed in the reverse bacterial mutation assay. These results indicate an important role of metabolism for the safety of GQD