Carbon Nanotubes and Graphene - Research and Applications

Multi-walled carbon nanotubes (MWNTs) have been proposed for use in many applications and concerns about their potential effect on human health have led to the interest in understanding the interactions between MWNTs and human cells. One important technique is the visualisation of the intracellular distribution of MWNTs. We exposed human macrophage cells to unpurified MWNTs and found that a decrease in cell viability was correlated with uptake of MWNTs due to mainly necrosis. Cells treated with purified MWNTs and the main contaminant Fe₂O₃ itself yielded toxicity only from the nanotubes and not from the Fe₂O₃. We used 3-D dark-field scanning transmission electron microscopy (DF-STEM) tomography of freeze-dried whole cells as well as confocal and scanning electron microscopy (SEM) to image the cellular uptake and distribution of unpurified MWNTs. We observed that unpurified MWNTs entered the cell both actively and passively frequently inserting through the plasma membrane into the cytoplasm and the nucleus. These suggest that MWNTs may cause incomplete phagocytosis or mechanically pierce through the plasma membrane and result in oxidative stress and cell death.

(Crystal Cheng, Karin H. Müller, Krzysztof K.K. Koziol, Jeremy N. Skepper, Paul A. Midgley, Mark E. Welland, and Alexandra E. Porter, Biomaterials 30, Issue 25, September 2009, Pages 4152-4160, doi:10.1016/j.biomaterials.2009.04.019)