RESUMO
Metallic nanoparticles such as silver (Ag), cerium dioxide (CeO2) and titanium dioxide (TiO2) are produced at a large scale and included in many consumer products. It is well known that most metallic NPs are toxic to humans which raise concerns about these engineered particles. Various studies have already been published on the subject, however, almost all of these studies have been conducted in cancer or transformed cell lines. In this work we performed a comparative evaluation of these metallic NPs on normal untransformed human fibroblasts (GM07492) detecting cyto- and geno-toxic responses after exposure to these NPs. Our results showed that all three metallic NPs were able to cross the plasma membrane and were mainly found in endocytic vesicles. The Ag and TiO2 NPs affected mitochondrial enzymatic activity (XTT), increased DNA fragmentation, oxidative damage (Comet assay) and induced cell death mainly by the apoptotic pathway. Ag NPs increased GADD45α transcript levels and the phosphorylation of proteins γH2AX. Transient genotoxicity was also observed from exposure to CeO2 NPs while TiO2 NPs showed no increase in DNA damage at sub-cytotoxic concentrations. In comparison, Ag NPs were found to be the most cyto-genotoxic NPs to fibroblasts. Thus, these results support the use of normal fibroblast as a more informative tool to detect the mechanisms of action induced by metallic NPs.
Assuntos
Cério/toxicidade , Fibroblastos/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Prata/toxicidade , Titânio/toxicidade , Ciclo Celular/efeitos dos fármacos , Proteínas de Ciclo Celular/genética , Morte Celular/efeitos dos fármacos , Linhagem Celular , Ensaio Cometa , Dano ao DNA , Fibroblastos/metabolismo , Histonas/metabolismo , Humanos , Proteínas Nucleares/genéticaRESUMO
We present for the first time an in-depth study of the RF response of a single-walled carbon nanotube (SWCNT) rope. Our novel electrode design, based on a tapered coplanar approach, allows for single tube measurements well into the GHz regime, minimizing substrate-related parasitics. From the analysis of the S-parameters, the ac transport mechanism in the range 30 kHz to 6 GHz is established. This work is an essential prerequisite for the fabrication of high-speed devices based on bundles of nanowires or low-dimensional structures.
