In vitro effects of ZnO and CuO NPs in mixture with DEP on A549 cells.

The main sources of ultrafine particles < 100 nm (UFPs) in urban areas and workplaces include combustion sources, especially diesel exhaust particles (DEP), but also non-exhaust sources or unintentional release of engineered nanoparticles (NPs). In a perspective of cumulative risk assessment is necessary to consider the possible interactive effects of different environmental stressor in biological systems. Commercially available (cZnO, cCuO < 50 nm) from Sigma-Aldrich) and sonochemically synthesized ZnO and CuO NPs (sZnO, sCuO), were used in mixtures with standard DEP (NIST 2975) to expose human lung A549 cells. NPs and mixtures were characterized by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). Cells were exposed for 24 h to mixtures consisting of DEP at a sub-toxic concentration and ZnO or CuO at increasing concentrations. At the end of the exposure, the cytotoxicity was assessed by MTT and Colony Forming Efficiency (CFE) assays, the Inflammatory response was evaluated using ELISA assay for Interleukin-8, and the cell morphology was investigated by fluorescence microscopy. The most hazardous single NPs resulted to be the cCuO ones, while the mixtures that more affect the viability were the DEP+ZnO ones. The different response towards DEP+sZnO and DEP+cZnO with respect to the individual ZnO NPs could be attributed to a possible different mechanism of interaction and endocytosis of the NMs once in mixture. In conclusion, by changing the physicochemical properties of NMs, the co-exposure with environmental UFP may modulate the biological responses. This aspect would be very useful for risk assessment and for the design of safer NMs.