Investigação da genotoxicidade e ecotoxicidade de nanoesferas de carbono

Abstract

Last decades several techniques for carbon materials synthesis have been developed aiming to produce new nanostructures. Among these, there are carbon nanospheres (CNS) defined as 50 to 1000 nm diameter spheres. Despite of their excellent performance in various fields as drug delivery, heterogeneous catalysis, encapsulation of support and electrode materials, few data are available about their toxicity. The present work investigated ecotoxicity and genotoxicity of CNS, including evaluation of their synthesis residues, aiming to contribute to product safety data sheets. Physicochemical characterization of CNS produced by chemical vapor deposition method (US 8722007 B2 patent) in a partnership among Petrobras and Brazilian Army Technology Center was performed. A multitrophic level test battery consisted of the following assays was performed: <i>Vibrio fischeri</i> 30min luminescense, <i>Daphnia similis</i> 48h imobility, <i>Ceriodaphnia dubia</i> 48h imobility, <i>Ceriodaphnia dubia</i> 8d reproduction, Danio rerio embryo 96h survival and <i>Grandidierella bonnieroides</i> 10d survival. Biocompatibility of CNS was evaluated throught citotoxicty assays which detect different endpoints as mitochondrial activity by WST-1 kit (Roche Applied Science) and cell membrane damage by LDH kit (Roche Applied Science) and cytokinesis-block micronucleus test using different cell lines (A549, HepG2 and RAW2647). Organic extracts of CNS was analised using citotoxicity assays and Salmonella/microsome assay to verify mutagenic potencial. The CNS particles presented 165 nm mean diameter, size range: 50 to 600nm, surface area of 26 m2/g and the presence of polycyclic aromatic hydrocarbons on their surface. The results obtained for acute exposures of aquatic animals were EC50 38 mg.L-1 to <i>Vibrio fischeri</i>, 25 mg.L-1 to <i>D.similis</i>, 8 mg.L-1, <i>C. dubia</i> and >10g/Kg dry weight sediment to <i>G.bonnieroides</i>. Subchronic exposure of zebrafish embryos showed LC50 >50 mg.L-1 and nonsignificant development alterations. Lastly, the reproduction decreasing of <i>C.dubia</i> presented NOEC 5mg.L-1. Cells incubated with CNS did not present loss of viability measured through mitochondrial activity but showed cell membrane damage without concentration-response relationship. After exposure, the material did not induce the formation of micronuclei in cells, for all strains tested. CNS extracts induced mutagenicity in TA98 and TA100 strains in presence of exogenous metabolization with mutagenic potency of 87 and 38 revertants per milligram of material. No mutagenic response was detected in TA98, TA100, YG1021 and YG1024 strains without exogenous metabolization. Cytotoxic effect was not observed for CNS extracts in A549 cells.