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Engineered amorphous silica nanoparticles (nanosilica) are one of the most abundant nanomaterials and are widely used in industry. Furthermore, novel nanosilica materials are promising theranostic tools for biomedicine. However, hazardous effects of nanosilica especially after inhalation into the lung have been documented. Therefore, the safe development of nanosilica materials urgently requires predictive assays to monitor toxicity. Here, we further investigate the impact of the protein corona on the biological activity of two different types of nanosilica (colloidal and pyrogenic) in lung cells. As previously described, adsorption of serum proteins to the nanosilica surface suppresses cytotoxicity in macrophages and lung epithelial cells. As the increase of pro-inflammatory mediators is a hallmark of inflammation in the lung upon nanosilica exposure, we studied the potential coupling of the cytotoxic and pro-inflammatory response in A549 human lung epithelial cells and RAW264.7 mouse macrophages. Indeed, cytotoxicity precedes the onset of pro-inflammatory gene expression and cytokine release as exemplified for IL-8 in A549 cells and TNF-alpha in RAW264.7 macrophages after exposure to 0-100 µg/mL nanosilica in medium without serum. Formation of a protein corona not only inhibited cellular toxicity, but also the pro-inflammatory response. Of note, uptake of nanosilica into cells was negligible in the absence, but enhanced in the presence of a protein corona. Hence, the prevailing explanation that the protein corona simply interferes with cellular uptake thus preventing adverse effects needs to be revisited. In conclusion, for the reliable prediction of adverse effects of nanosilica in the lung, in vitro assays should be performed in media not complemented with complete serum. However, in case of different exposure routes, e.g., injection into the blood stream as intended for biomedicine, the protein corona prevents acute toxic actions of nanosilica.

Background: Nanoparticle (NPs) functionalization has been shown to affect their cellular toxicity. To study this, differently functionalized silver (Ag) and gold (Au) NPs were synthesised, characterised and tested using lung epithelial cell systems. Methods: Monodispersed Ag and Au NPs with a size range of 7 to 10 nm were coated with either sodium citrate or chitosan resulting in surface charges from -50 mV to +70 mV. NP-induced cytotoxicity and oxidative stress were determined using A549 cells, BEAS-2B cells and primary lung epithelial cells (NHBE cells). TEER measurements and immunofluorescence staining of tight junctions were performed to test the growth characteristics of the cells. Cytotoxicity was measured by means of the CellTiter-Blue ® and the lactate dehydrogenase assay and cellular and cell-free reactive oxygen species (ROS) production was measured using the DCFH-DA assay. Results: Different growth characteristics were shown in the three cell types used. A549 cells grew into a confluent mono-layer, BEAS-2B cells grew into a multilayer and NHBE cells did not form a confluent layer. A549 cells were least susceptible towards NPs, irrespective of the NP functionalization. Cytotoxicity in BEAS-2B cells increased when exposed to high positive charged (+65-75 mV) Au NPs. The greatest cytotoxicity was observed in NHBE cells, where both Ag and Au NPs with a charge above +40 mV induced cytotoxicity. ROS production was most prominent in A549 cells where Au NPs (+65-75 mV) induced the highest amount of ROS. In addition, cell-free ROS measurements showed a significant increase in ROS production with an increase in chitosan coating. Conclusions: Chitosan functionalization of NPs, with resultant high surface charges plays an important role in NP-toxicity. Au NPs, which have been shown to be inert and often non-cytotoxic, can become toxic upon coating with certain charged molecules. Notably, these effects are dependent on the core material of the particle, the cell type used for testing and the growth characteristics of these cell culture model systems. [ABSTRACT FROM AUTHOR]

Nickel, zinc, and copper oxide nanoparticles (NiONP, ZnONP, and CuONP) and their aqueous extracts (AEs) were applied to A549 lung epithelial cells to determine the cytotoxicity, IL-8 production, and activation of transcription factors. Nanoparticles (NPs) and their AEs were also instilled into rat lungs to evaluate acute and chronic inflammatory effects. In vitro AEs had specific effects; for example NiOAE had no effect and ZnOAE affected all parameters measured. NPs themselves all had cytotoxic effects but only ZnONP and CuONP impacted pro-inflammatory endpoints. The inflammatory cells in the BAL were also different from AEs and NPs with ZnONP and CuONP recruiting eosinophils and neutrophils whilst ZnOAE and CuOAE elicited only mild neutrophilic inflammation that had resolved by four weeks. NiONP recruited neutrophils only whilst NiOAE did not cause any inflammation. Understanding differences in the toxic role of the ionic components of metal oxide NPs will contribute to full hazard identification and characterisation. [ABSTRACT FROM AUTHOR]

Abstract: Single-walled carbon nanotubes have gained enormous popularity due to a variety of potential applications which will ultimately lead to increased human and environmental exposure to these nanoparticles. This study was carried out in order to evaluate the inflammatory response of immortalised and primary human lung epithelial cells (A549 and NHBE) to single-walled carbon nanotube samples (SWCNT). Special focus was placed on the mediating role of lung surfactant on particle toxicity. The toxicity of SWCNT dispersed in cell culture medium was compared to that of nanotubes dispersed in dipalmitoylphosphatidylcholine (DPPC, the main component of lung lining fluid). Exposure was carried out for 6 to 48 h with the latter time-point showing the most significant responses. Moreover, exposure was performed in the presence of the pro-inflammatory stimulus tumour necrosis factor-α (TNF-α) in order to mimic exposure of stimulated cells, as would occur during infection. Endpoints evaluated included cell viability, proliferation and the analysis of inflammatory mediators such as interleukin (IL)-8, IL-6, TNF-α and macrophage chemoattractant protein-1 (MCP-1). Crocidolite asbestos was included as a well characterised, toxic fibre control. The results of this study showed that HiPco SWCNT samples suppress inflammatory responses of A549 and NHBE cells. This was also true for TNF-α stimulated cells. The use of DPPC improved the degree of SWCNT dispersion in A549 medium and in turn, leads to increased particle toxicity, however, it was not shown to modify NHBE cell responses. [Copyright &y& Elsevier]