How Toxic are Nanoparticles?

That's the ultimate questions with the new technology. A piece in Neue Zürcher Zeitung (10. 5. 2006) reports that Swiss researchers develop a test system for nanoparticles to measure their effect on cell cultures. Obviously the rule of thumb "the tinier, the more toxic" or "more surface area, more impact" isn't true in any case: tiny carbon nanotubes stick together to form larger objects with spear-like performance to the cells. Zinc oxide (ZnO2) destroyed cells similar to asbestos; whilst ferric oxide damages cells of the lung, but not of connective tissue. Obviously, the impact depends on the cell type and the material.