Nanotubes' toxic effects 'similar to asbestos'
来源：未知 作者：苍孟民 时间：2019-03-01 09:14:06
By Colin Barras Injecting carbon nanotubes into mice shows they can trigger similar toxic responses to asbestos fibres, causing a strong immune response and possibly cancer in the abdominal cavity, researchers say. But another recent study suggests the tiny tubes, which are increasingly appearing in commercial and industrial products, are not dangerous when inhaled, probably because they do not persist in the body as asbestos fibres do. Carbon nanotubes (CNTs) first came to the attention of researchers in the early 1990s. Incredibly strong for their size and able to function as both conductors and semiconductors, the tiny structures are thought to be ideal for applications that range from drug delivery to space elevators. But under a microscope, some CNTs look identical to asbestos fibres, leading to concerns that they could cause similar health problems. Occupational exposure to asbestos led to widespread lung disease, and cancers known as mesothelioma, in the 20th century. Asbestosis research revealed a checklist of features that makes the fibres dangerous, says Ken Donaldson at the University of Edinburgh, UK. Ever since, it was presumed that any needle-like fibres around 20 micrometers long with an ability to persist in the body could have similarly dangerous effects. Donaldson and colleagues have now shown this holds true for carbon nanotubes. When they injected multi-walled carbon nanotubes – composed of a hierarchy of tubes within tubes – into the abdominal cavity of mice, they saw a strong immune reaction within seven days to tubes longer than 20 micrometers. Lesions known as granulomas had developed in the tissue surrounding the abdominal organs. The granulomas form when the macrophage immune cells that usually swallow and neutralise foreign particles take on the tubes. The cells get ruptured and die when they try to swallow fibres longer than 20 micrometers. But Donaldson points out that his study does not reveal whether nanotubes are able to persist in the body long enough to reach the areas he directly injected them into. “We need to show this result in an inhalation study,” he says. James Bonner at the North Carolina State University, Raleigh, US, will shortly publish one of the first such studies. In his experiments, mice breathed air containing 40-micrometer-long multi-walled nanotubes. “Very little inflammatory or fibrogenic effect was observed,” he says. Donaldson notes that determining the true risks of nanotubes will involve measuring the ways in which people will be exposed to them, something studies on toxicity cannot judge. There is little evidence about exposure so far, says Donaldson. “But the good news is that nanotubes are probably not very ‘dirty’,” he says. “They are quite highly charged and stick together, so they don’t seem to get airborne easily.” Journal reference: Nature Nanotechnology (DOI: