BackgroundEngineered nanomaterials display unique properties that may have impact on human health, and thus require a reliable evaluation of their potential toxicity. Here, we performed a standardized in vitro screening of 23 engineered nanomaterials. We thoroughly characterized the physicochemical properties of the nanomaterials and adapted three classical in vitro toxicity assays to eliminate nanomaterial interference. Nanomaterial toxicity was assessed in ten representative cell lines.ResultsSix nanomaterials induced oxidative cell stress while only a single nanomaterial reduced cellular metabolic activity and none of the particles affected cell viability. Results from heterogeneous and chemically identical particles suggested that surface chemistry, surface coating and chemical composition are likely determinants of nanomaterial toxicity. Individual cell lines differed significantly in their response, dependent on the particle type and the toxicity endpoint measured.ConclusionIn vitro toxicity of the analyzed engineered nanomaterials cannot be attributed to a defined physicochemical property. Therefore, the accurate identification of nanomaterial cytotoxicity requires a matrix based on a set of sensitive cell lines and in vitro assays measuring different cytotoxicity endpoints.

Data from the Ion Mass Analyser (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analysed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO + 2 /O + and O + 2 /O + . The following ratios averaged over all events and energies were identified: CO + 2 /O + =0.2 and O + 2 /O + =0.9. The values measured are significantly higher, by a factor of 10 for O + 2 /O + , than a contemporary modeled ratio for the maximum fluxes which the Martian ionosphere can supply. The most abundant ion species was found to be O + , followed by O + 2 and CO + 2 . We estimate the loss of CO + 2 to be 4.0 · 10 24 s −1 (0.29 kg s −1 ) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.

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