Depending on the cell type cerium dioxide nanoparticles induce different biological responses in vitro. Only a small number of studies demonstrate a toxic effect of these nanoparticles, in many cases the cerium dioxide nanoparticles protect the cells by scavenging oxygen radicals in the cells.

 

Various in vitro studies with nanoscale cerium dioxide particles could demonstrate that these metal oxide nanoparticles induce different responses within the cells dependent on the cell type investigated [1, 2]. For human lung epithelial cells (BEAS-2B) treated in vitro with various metal oxide nanoparticles it has been shown that these pure metal oxides could not induce inflammatory mediators [3]. On the contrary, in the human lung epithelial cell line A549 the cell viability decreased in one study dependent on the particle concentration [4], whereas another study could not observe such a cytotoxic effect by nanoscale cerium dioxide [5]. The human immune cell line Jurkat could be protected by CeO2 against cell-damaging UV-light [6]. The same protection effect could be demonstrated for various lung cells of rats. In this case the cerium dioxide nanoparticles serve as antioxidant and reduce the production of reactive oxygen species (ROS) [7].

 

Only a small number of studies found toxic effects induced by CeO2 in cells in culture [1, 4]. Most common is the induction of oxidative stress responses, which may be followed by cell death. On the other hand, studies demonstrating exactly the opposite, are in majority. Because of its chemical properties it can be observed that CeO2 prevents the production of oxygen radicals and protects by this the cells from cell death [6-8]. Within a series of in vitro experiments with the human lung epithelial cell line A549 the project consortium NanoCare has described a relatively high threshold limit for toxicity of CeO2. Only such high concentrations (defined as lowest observed effect level - LOEL) can induce stress responses as well as the production of inflammatory marker and reactive oxygen species (ROS). Lower concentrations of cerium dioxide could not induce any toxic effect in different cell lines [9]. This was confirmed by a recent review, which presents an overview about the important studies on various nanomaterials [2]. Herein it is mentioned that the size of the CeO2 particles is not important for an effect. Moreover, the toxicity is described as very low, which is possibly a result of the protective effect against ROS.

 

Additionally to the very simple monoculture system with only one cell line the project NanoCare used also more complex co-culture systems [9]. Such systems compare much better to the original situation within the organism as the interaction between different cell types can be simulated. It could be demonstrated that co-cultures respond more sensitive to CeO2 compared to monoculture. This may be the result of communication between the cells which can enhance the overall reaction.

 

 

Literature arrow down
  1. Mittal, S. & Pandey, A.K.(2014), Biomed Res Int, 2014891934.
  2. Simko, M. et. al. (2015), Int J Mol Sci, 16(11): 25954.
  3. Veranth, J.M. et. al. (2007), Part Fibre Toxicol, 42.
  4. Lin, W. et. al. (2006), Int J Toxicol, 25(6): 451-457.
  5. Park, B et al. (2008), Inhal Toxicol, 20(6): 547-566.
  6. Caputo, F. et. al. (2015), Nanoscale, 7(38): 15643-15656.
  7. Dunnick, K.M. et. al. (2015), Biol Trace Elem Res, 166(1): 96-107.
  8. Hirst, S.M. et. al. (2013), Environ Toxicol, 28(2): 107-118.
  9. Nanocare (2009). Report:"Final Scientific Report", Dechema e.V., Frankfurt a.Main. ISBN:978-3-89746-108-6 (pdf, 19MB).

 

 

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