Influence of serum on in situ proliferation and genotoxicity in A549 human lung cells exposed to nanomaterials

In this work in situ proliferation of A549 human lung epithelial carcinoma cells exposed to nanomaterials (NMs) was investigated in the presence or absence of 10% serum. NMs were selected based on chemical composition, size, charge and shape (Lys-SiO(2), TiO(2), ZnO, and multi walled carbon nanotubes, MWCNTs). Cells were treated with NMs and 4h later, cytochalasin-B was added. 36 h later, cell morphology was analyzed under a light microscope. Nuclearity was scored to determine the cytokinesis-block proliferation index (CBPI). CBPI, based on percentage of mono-, bi- and multi-nucleated cells, reflects cell toxicity and cell cycle delay. For some conditions depending on NM type (TiO(2) and MWCNT) and serum concentration (0%) scoring of CBPI was impossible due to overload of agglomerated NMs. Moreover, where heavy agglomeration occurs, micronuclei (MN) detection and scoring under microscope was prevented. A statistically significant decrease of CBPI was found for ZnO NM suspended in medium in the absence or presence of 10% serum at 25 μg/ml and 50 μg/ml, respectively and for Lys-SiO(2) NM at 3.5 μg/ml in 0% serum. Increase in MN frequency was observed in cells treated in 10% serum with 50 μg/ml ZnO. In 0% serum, the concentrations tested led to high toxicity. No genotoxic effects were induced by Lys-SiO(2) both in the absence or presence of serum up to 5 μg/ml. No toxicity was detected for TiO(2) and MWCNTs in both 10% and 0% serum, up to the dose of 250 μg/ml. Restoration of CBPI comparable to untreated control was shown for cells cultured without serum and treated with 5 μg/ml of Lys-SiO(2) NM pre-incubated in 100% serum. This observation confirms the protective effect of serum on Lys-SiO(2) NM cell toxicity. In conclusion in situ CBPI is proposed as a simple preliminary assay to assess both NMs induced cell toxicity and feasibility of MN scoring under microscope.