RESUMEN
Niobium (V) oxide nanoparticles (NINPs) have been widely and increasingly applied in various health products and industrial processes. This merits further study of their toxicity. Here, we investigated the potential of NINPs to induce DNA damage, cytotoxicity, and chromosome instability in cultured CHO-K1 cells. NINPs were physico-chemically characterized. As assessed by comet assay, crystalline and amorphous NINPs were genotoxic at the highest concentrations evaluated. The cytokinesis-block micronucleus assay demonstrated that a 24-h treatment with NINPs, for the crystalline and the amorphous samples, significantly reduced the nuclear division cytotoxicity index. In addition, a 4-h treatment period of crystalline NINPs increased micronucleus (MNi) frequencies. MNi, nucleoplasmic bridges and nuclear buds were detected after exposure of the cells for 24 h to crystalline NINPs. In the amorphous sample, chromosome instability was restricted to the induction of MNi, in the 24-h treatment, detected at all tested concentrations. The fluorescence and dark field microscopy demonstrated the uptake of NINPs by CHO-K1 cells and an intracellular distribution outlining the nucleus. Our data advance understanding of the cytotoxic and genotoxic effects of NINPs and should be taken into consideration when setting up guidelines for their use in industrial or health products.
RESUMEN
The genotoxicity and cytotoxicity of water in small urban basins was evaluated by the Salmonella/microsome assay and micronucleus test in V79 cells. The results showed that the cytotoxic effect was the most significant response in areas with medium to heavy urban occupation for both assays evaluated. Water samples from these areas include different concentrations of chloroform, bromodichloromethane, toluene, ethylbenzene, m,p-xylene and 1,4-dichlorobenzene. As to genotoxic damage, the presence of mainly direct-acting frameshift mutagens was detected in areas with less urban concentration and showed genotoxic activity in V79 cells in more heavily urbanized areas. Water organic extracts, evaluated using a microsuspension procedure, showed frameshift mutagenic activity in the presence of hepatic metabolization that increased as the population density grow. Chronic toxicity studies of sediment samples with the microcrustacean Daphnia magna showed that, while survival was not highly affected, reproductive inhibition was found in 92% of the observations. A retrospective diagnosis of water quality using traditional physicochemical parameters that defined the differential contribution of urban wastes at the three sites was associated with the biological assays. It became clear that the biological assays were of significant benefit in the diagnosis of risks of contamination of hydrographic basins by pollutants from urban non-point sources.
