Most of the in vitro studies carried out reveal a relatively high toxicity of zinc oxide (ZnO) nanoparticles for cells of different tissues and different organisms.

 

The very steep dose-effect curves found for the ZnO particles indicate that from a certain concentration, the toxic effect increases very rapidly. For most cell types, the relevant value is in the range of 10-20 µg/ml.

The studies carried out within the project NanoCare on eleven different cell lines of different origins show that these cell lines are differently sensitive to the ZnO particles. Here, too, a relatively high toxicity was found already at low concentrations in some cell lines (LOEL from 5 g/cm2 or approximately 16 µg/ml). For some cells, the threshold values for in vitro apoptosis tests were in the range of 7,5-10 µg/cm2 [1].

 

In addition to simple culture systems with only one cell line, also complex so-called co-culture systems were used within NanoCare. Using such systems, the in vivo situation in the body can be displayed better due to simulation of the interaction of the cells. In these systems, ZnO particles were found to cause increased levels of inflammation markers [1].

 

The mechanism responsible for the high toxicity of ZnO particles has not yet been completely clarified. It seems, however, that released zinc ions and reactive oxygen radicals are playing an important role [2,3]. Likewise, it is not yet clear whether the observed toxic effect is influenced by the shape and size of the ZnO particles. According to several studies, however, there are no traceable size-dependent effects [3,4,5,6].

 

Coating with gold or aluminum was found to strongly reduce the toxicity of the ZnO nanoparticles [7,8,9]. It was postulated, therefore, that the cellular effects are rather caused by electronic properties or solubility than by the size of particles. ZnO nanoparticles are of interest to medical applications due to the possibility of changing their toxicity through selective modifications [10]. Since ZnO nanoparticles seem to be very toxic to cancer cells, (that is, also to many cell lines used in cell culture systems) but not to normal cells [11,12], they are investigated, in addition, for their potential cancer fighting capability and their ability to serve as drug-administrating vehicles.

 

Literature arrow down

  1. NanoCare 2009, Final Scientific Report, ISBN 978-3-89746-108-6. (PDF-Document, 19 MB).
  2. Xia, T et al. (2008), ACS Nano, 2(10): 2121-2134.
  3. Song, W et al. (2010), Toxicol Lett, 199(3): 389-397.
  4. Lin, WS et al. (2009), J Nanopart Res, 11(1): 25-39.
  5. Deng, X et al. (2009), Nanotechnology, 20(11): 115101.
  6. Yuan, JH et al. (2010), Colloids Surf B Biointerfaces, 76(1): 145-150.
  7. Xu, M et al. (2010), Biomaterials, 31(31): 8022-8031.
  8. George, S et al. (2009), ACS Nano, 4(1): 15-29.
  9. Yin, H et al. (2010), Langmuir, 26(19): 15399-15408.
  10. Rasmussen, JW et al. (2010), Expert Opin Drug Deliv, 7(9): 1063-1077.
  11. Hanley, C et al. (2008), Nanotechnology, 19(29): 295103.
  12. Wang, H et al. (2009), J Mater Sci Mater Med, 20(1): 11-22.

 

 

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