Carbon nanotubes (CNTs) can be internalised through different mechanisms by cells. With the exception of extremely long and stiff carbon nanotubes, internalised CNTs seem to have no significant impact on the cells.


Paradigm of frustrated phagocytosis for asbestos fibres and carbon nanotubes. Paradigm of frustrated phagocytosis for asbestos fibres and carbon nanotubes. Without any stabilising additives, nanomaterials and also carbon nanotubes (CNTs) tend to agglutinate very rapidly. Since such agglomerates can be larger than a normal cell, the cells would rather "choke to death" on the carbon nanotubes (frustrated phagocytosis) than take them up.

Smaller agglomerates are taken up by the cells via pinocytosis and can be detected inside the cells by means of electron microscopy (TEM) in cell inclusions (so-called vesicles). The vesicular membrane protects the remaining cell components from the carbon nanoparticles, which means that the nanoparticles are inside the cells but still encapsulated. However, one study showed the possibility of CNTs to escape these encapsulations and to reach the cytoplasm of the cells [1-4].


Modified carbon nanotubes, which can overcome normally insurmountable biological barriers due to modified surface properties, are of great interest to medical and biotechnological applications. In contrast to non-modified CNTs, the functionalised carbon nanotubes do not agglomerate in aqueous environments and are therefore available as individual tubes [5]. Due to their shapes and sizes, these CNTs can enter cells via an alternative, vesicle-independent path. Recent studies have proven that specific contents of lung surfactant (proteins and lipids) produce such a "biological functionalisation" of multi-walled carbon nanotubes, which does not affect the cytotoxicity of multi-walled CNTs [6-8].


So far, it has not yet been adequately explained in which way the CNTs can leave the cells afterwards and whether they accumulate inside the cells.



Literature arrow down

  1. Monteiro-Riviere, NA et al. (2005), Toxicol Lett, 155(3): 377-384.
  2. Porter, AE et al. (2009), ACS Nano, 3(6): 1485-1492.
  3. Conner, SD et al. (2003), Nature, 422(6927): 37-44.
  4. Mu, Q et al. (2009), Nano Lett, 9(12): 4370-4375.
  5. Kostarelos, K et al. (2007), Nat Nanotechnol, 2(2): 108-113.
  6. Gasser, M et al. (2010), J Nanobiotechnology, 8 31.
  7. Gasser, M et al. (2012), Part Fibre Toxicol, 9 17.
  8. Schleh, C et al. (2013), Part Fibre Toxicol, 10 6.



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