New materials of emerging technological importance are single-walled carbon nanotubes (SWCNTs). Because SWCNTs will be used in commercial products in huge amounts, their effects on human health and the environment have been addressed in several studies. Inhalation studies in vivo and submerse applications in vitro have been described with diverging results. Why some indicate a strong cytotoxicity and some do not is what we report on here. Data from A549 cells incubated with carbon nanotubes fake a strong cytotoxic effect within the MTT assay after 24 h that reaches roughly 50%, whereas the same treatment with SWCNTs, but detection with WST-1, reveals no cytotoxicity. LDH, FACSassisted mitochondrial membrane potential determination, and Annexin-V/PI staining also reveal no cytotocicity. SWCNTs appear to interact with some tetrazolium salts such as MTT but not with others (such as WST-1, INT, XTT). This interference does not seem to affect the enzymatic reaction but lies rather in the insoluble nature of MTT−formazan. Our findings strongly suggest verifying cytotoxicity data with at least two or more independent test systems for this new class of materials (nanomaterials). Moreover, we intensely recommend standardizing nanotoxicological assays with regard to the material used: there is a clear need for reference materials. MTT−formazan crystals formed in the MTT reaction are lumped with nanotubes and offer a potential mechanism to guide bioremediation and clearance for SWCNTs from "contaminated" tissue. SWCNTs are good supporting materials for tissue growth, as attachment of focal adhesions and connections to the cytoskeleton suggest.

Metal oxides may hold, as nanosized particles, a toxic potential to human health and the environment that is not present in the bulk material. Due to the high surface-to-volume ratio, small amounts can lead to strong oxidative damage within biological systems, impairing cellularfunctions as a consequence of their high surface reactivity. We report here on a new nanosized V203 material that has a needle-like structure with diameters of less than 30 nm and variable lengths. The potentiated toxicity of nanoscale vanadium oxide (V203) compared to bulk material is demonstrated here in human endo- and epithelial lung cells, and might be due to the higher catalytic surface of the particles. Reduction in cell viability is almost ten times stronger and starts with lowest concentrations of "nanoscaled" material (10 microg/mL). Vanadium oxide leads to an induction of heme oxygenase 1 (HO-1) in a dose dependent manner in ECV304 cells whereas a reduction in protein levels can be observed for the epithelial cells (A549). Lipid peroxidation can be observed also for "nanoscaled" vanadium oxide to a much stronger extent in macrophages (RAW cells) than for bulk material. The observed effects can not only be explained by oxidation from V2O3 to V2O5 as there are significant differences between the novel nano vanadium and all used bulk materials (V203 and V205). It appears rather to be a nanoeffect of a high surface reactivity, here coupled with a yet unknown toxicity potentiating effect of a technically important catalyst.

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The sections in this article are Introduction Nanoscale Materials and Adverse Health Effects: Precautionary Measures Hazard Identification and Exposure Estimation Production and Use of “New Carbon Modifications” and Metal Oxides Health Aspects Uptake and Possible Transport, Depots, and Accumulation in Living Organisms Biological Effects on Cellular Mechanisms Metal Oxides New Carbon Modifications Possible Hazards – Toxicological Impacts Risk Characterization – A Conclusion Opportunities and Risks of Nanomaterials New Materials without Risks?

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