Abstract
BackgroundDue to its antibacterial properties, silver (Ag) has been used in more consumer products than any other nanomaterial so far. Despite the promising advantages posed by using Ag-nanoparticles (NPs), their interaction with mammalian systems is currently not fully understood. An exposure route via inhalation is of primary concern for humans in an occupational setting. Aim of this study was therefore to investigate the potential adverse effects of aerosolised Ag-NPs using a human epithelial airway barrier model composed of A549, monocyte derived macrophage and dendritic cells cultured in vitro at the air-liquid interface. Cell cultures were exposed to 20 nm citrate-coated Ag-NPs with a deposition of 30 and 278 ng/cm2 respectively and incubated for 4 h and 24 h. To elucidate whether any effects of Ag-NPs are due to ionic effects, Ag-Nitrate (AgNO3) solutions were aerosolised at the same molecular mass concentrations.ResultsAgglomerates of Ag-NPs were detected at 24 h post exposure in vesicular structures inside cells but the cellular integrity was not impaired upon Ag-NP exposures. Minimal cytotoxicity, by measuring the release of lactate dehydrogenase, could only be detected following a higher concentrated AgNO3-solution. A release of pro-inflammatory markers TNF-α and IL-8 was neither observed upon Ag-NP and AgNO3 exposures as well as was not affected when cells were pre-stimulated with lipopolysaccharide (LPS). Also, an induction of mRNA expression of TNF-α and IL-8, could only be observed for the highest AgNO3 concentration alone or even significantly increased when pre-stimulated with LPS after 4 h. However, this effect disappeared after 24 h. Furthermore, oxidative stress markers (HMOX-1, SOD-1) were expressed after 4 h in a concentration dependent manner following AgNO3 exposures only.ConclusionsWith an experimental setup reflecting physiological exposure conditions in the human lung more realistic, the present study indicates that Ag-NPs do not cause adverse effects and cells were only sensitive to high Ag-ion concentrations. Chronic exposure scenarios however, are needed to reveal further insight into the fate of Ag-NPs after deposition and cell interactions.
Highlights
Due to its antibacterial properties, silver (Ag) has been used in more consumer products than any other nanomaterial so far
Particle exposure and characterisation Inductively coupled plasma mass spectrometry (ICPMS) measurements showed that the stock solutions have an Ag concentration of 6 μg/mL
The distribution and the state of agglomeration of the deposited NPs was qualitatively analysed with transmission electron microscopy (TEM) by particle exposure onto TEM grids (Figure 1A and B)
Summary
Due to its antibacterial properties, silver (Ag) has been used in more consumer products than any other nanomaterial so far. Despite the promising advantages posed by using AgNPs in such applications, the possible health effects associated with the inevitable human exposure to NPs [9,10] has raised concerns as to the mass use and production of Ag-NPs without having a clear understanding of their specific interaction with biological systems [11]. In regards to the human interaction with Ag-NPs, numerous different exposure routes exist: via the lung, skin, bloodstream and ingestion. It is assumed, that inhalation of Ag-NPs is of primary concern for humans in an occupational setting [13]
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