"We are among the first to describe the mechanism for carbon nanomaterial's toxicity at the molecular level," Fanqing Frank Chen of Lawrence Berkeley National Laboratory told nanotechweb.org. "Although there are other previous reports on carbon nanomaterial toxicity to various cells, there is no detailed, comprehensive molecular biology study available to give us a complete picture genome wide. We also validated and demonstrated that apoptosis [programmed cell death], cell-cycle delay, cellular transport, and inflammation are linked to the treatments."

Chen and colleagues found that exposure to the nanotubes and nano-onions activated genes involved in cellular transport, metabolism, cell-cycle regulation and stress response. Multi-walled carbon nanotubes induced genes related to a strong immune and inflammatory response, while the presence of nano-onions caused most changes in genes induced in response to external stimuli. The nanotubes appeared to be ten times more toxic than the nano-onions.

"One advantage of our approach is that it's a combination of hig- content imaging analysis and high-throughput genomics," said Chen. "The whole genome profiling of the treated cells also give us a very detailed picture of the effects."

According to Chen, the first application of the work will be providing safety guidelines for people working with nanotubes and nano-onions. "We can also use the same approach for other nanomaterials," he added. "Additionally, since the toxicity of carbon nanomaterials is quite long lasting, even though not as acute as lots of the conventional toxins, we're exploring using these nanomaterials for cancer treatments."

The researchers reported their work in Nano Letters.