Mostly, titanium dioxide (TiO2) particles are taken up as aggregates via vesicles into the cytoplasm of exposed cells.

 

Most of the TiO2 particles are taken up in the cells as large intracellular aggregates in vesicles, vacuoles or lamellar bodies by means of phagocytosis. High doses, however, impede phagocytosis thus causing overloading of the cells, for example in the lungs [5]. Pinocytotic uptake was observed only in the case of small aggregates (< 30nm) and single particles. After uptake, the TiO2 particles are mostly bound to the cytoplasmic membranes of the cells. No particles have been found so far in the nuclei of the cells [1,2]. In vitro multi-cell systems are preferred to simple cell culture models with only one cell type for simulation of the interaction of different cells in the body and of in vivo situations. Using sensitive methods, TiO2 was shown to occur in all cell types of a triple co-culture system as membrane-bound larger aggregates but also freely in the cytoplasm as smaller aggregates or single particles [3].

 

In contrast, transcytosis, i.e. the vesicular transport of macromolecules from one cell to the other, has hardly been investigated in vitro. Measurements that have been taken within the project NanoCare to assess the transport of nanoparticles through the cells have shown that TiO2 particles are not transported through monolayer cells [4]. Besides, exocytosis, a process where substances are transported from the cell interior to the cell environment, does not take place according to in vitro tests.

 

Literature arrow down

  1. L'Azou, B et al. (2008), Part Fibre Toxicol, 5 22.
  2. Zucker, RM et al. (2010), Cytometry A, 77(7): 677-685.
  3. Rothen-Rutishauser, B et al. (2007), Part Fibre Toxicol, 4 9.
  4. Schulze, C et al. (2008), Nanotoxicology, 2(2): 51-61.
  5. Li, J et al. (2007), Environ Toxicol Pharmacol, 24(3): 239-244.

 

 

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