In the first study, led by Deanna Thompson of the biomedical engineering department, researchers examined the effect of carbon nanotubes on the growth of rat heart muscle cells. This was to understand how the nanomaterials affect mammalian cells, tissues and organs. Unlike previous experiments that looked at how nanotube clusters affect cell growth, the new work studied the way both clusters and finely dispersed material, composed of small bundles of nanotubes and other nanoparticulate impurities, behave.
Thompson's team found that the finely dispersed materials, despite being in a low concentration, inhibited cell growth more than larger clusters of nanotubes. Moreover, activated carbon, a commonly used nanoporous carbon material, affects cells less than either the large aggregates or the finely dispersed material. These result were published in Toxicology Letters.
The second study, led by Anurag Sharma of the earth and environmental sciences department, investigated the growth of bacteria in the presence of carbon nanotubes to find out how nanoscale materials might impact the environment over long periods of time. The results revealed that, while the nanotubes sustained the growth of Escherichia Coli bacteria, they also elongated the E. Coli in some cases – something that has never been seen before. This discovery implies that the nanotubes may be affecting the biological activity of the bacteria via a form of stress. In contrast, the elongation was not seen with other carbon nanomaterials, such as activated carbon or C-60 fullerenes ("buckyballs").
Both studies suggest that different nanomaterials could affect human health and the environment in widely different ways. "These findings highlight the underlying need for further research to correlate in detail the different types of nanomaterials and their modes of interaction with biological systems, to promote safe and optimized applications of nanotechnology," said Pavan Raja, who worked with both research teams.
The research from the two groups was presented at the 23rd American Chemical Society National Meeting in Chicago this week.