Cytotoxicity of metal oxide nanoparticles to the lung and immune cells in vitro: a contribution to safer nanoantibacterials

Kaja KASEMETS, University of Milano Bicocca and NICPB, Tallin - Estonia

Nano metal oxides as ZnO, CuO and TiO2 have been proven efficient for the antibacterial coatings of fabrics. Use of nano-antimicrobial coated textiles for consumer or medical purposes needs wide range of toxicological studies to ensure their effective and safe use.

The aim of the study was to evaluate the cytotoxic and pro-inflammatory effect of sonochemically synthesized ZnO, CuO and Zn-doped CuO (nZnCuO) NPs to the human lung epithelial A549 and macrophage-like THP-1 cells. Lung and immune cells were investigated as the inhalation is considered a primary exposure route of the nano-enabled materials for human in occupational and everyday life.

Respective metal acetate-salt in water or ethanol-water mixture and ultrasounds were used for the particles synthesis and coating of fabrics. The high resolution SEM analyses showed different size and shape of the NPs. Hydrodynamic size evaluation by DLS (Malvern Zetasizer) showed that the particles were agglomerated and tended to settle in the cell culture medium.

For toxicity assessment, cells were exposed to the studied NPs on 6-multi-well plates in OptiMEM medium without serum for 3 and 24 h. MTT-based viability and secretion of interleukin 8 (IL-8) as pro-inflammatory marker was assessed.

Results showed reduced cell viability in the lung and immune cells after 3 h exposure only at high NPs concentrations (100 mg/mL) and after 24 h the EC50 values for all the studied particles were ~20 mg/mL. No clear difference in the cells responses can be associated to the NPs size and shape. Even the highly antimicrobial ZnCuO NPs were comparable to those of nCuO.

Nanoparticles had also pro-inflammatory effect on the lung and immune cells. After 24-h exposure nCuO induced IL-8 release in lung cells already at the sub-toxic concentrations (1-10 mg/mL) and nZnO at higher concentrations in both cells lines. As the pro-inflammatory response can be due to the oxidative stress, the role of reactive oxygen species is under investigation and will be discussed.

Very little amount of particles were released from the coated fabrics in abrasion test. Although the NPs were not toxic to the lung and immune cells at low environmentally-realistic exposure concentrations, the particles pro-inflammatory profile could suggest considered nZnO safer than nCuO for the antibacterial coating of textiles. Of course, this conclusion needs more stringent toxicological evidence.

This work was supported by Fondazione Cariplo (OverNanotox 2013-0987).

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