Credit: © 2007 ACS

In vitro measurements that attempt to predict the toxicity of nanomaterials can be useful, but extrapolating these results to in vivo studies still remains a challenge. Previous studies with several types of nanoparticles have found little correlation, for example, between lung toxicity observed in cell cultures and in rats. Now, a study conducted by researchers from DuPont Haskell Laboratory for Health and Environmental Sciences in the US shows that this discrepancy also holds for fullerene nanoparticles.

David Warheit and colleagues1 inserted pristine fullerenes (C60) and C60 functionalized with hydroxyl groups into the lungs of rats and assessed their toxicity after one day, one week and one and three months. Various cytotoxicity biomarkers, such as lactate dehydrogenase and lipid peroxidation, were measured in the fluid obtained from the lungs of the rats and no significant increase in these markers was seen compared with a control group of animals that were only exposed to water. Exposure to both types of fullerenes showed only transient inflammation in the lungs after one day and did not persist over time. No adverse lung tissue effects were seen after three months in rats that were exposed to the highest doses of both types of fullerenes.

These findings are inconsistent with previous in vitro studies, where significant cytotoxic effects were seen in three different types of cells. It is clear that better and more standardized in vitro systems are required before they can be a useful toxicity screening method.