Abstract
BackgroundCarbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both.MethodsPrintex®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea.ResultsAll particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo.ConclusionsOur results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.
Highlights
Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements
Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound polycyclic aromatic hydrocarbons (PAH), and varies in different target cells
We used four CBNP: P90, P90 coated with BaP (P90-BaP), P90 coated with 9NA (P90-9NA), and, to model nanoparticles that acquire PAH during synthesis, a soot derived from acetylene combustion that contains various PAHs (AS-PAH)
Summary
Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). CBNP are potentially harmful since their large surface area can interact with biological systems [1, 9,10,11,12,13,14] Substances such as polycyclic aromatic hydrocarbons (PAHs) that are intrinsically toxic can be adsorbed during CBNP synthesis [15]. The theory that the toxicity of CBNP can be increased by other substances has been validated by the application of metal ions, which increased the toxicity due to autophagy and lysosomal dysfunction [16] It is still not clear how direct binding of chemical add-ons to CBNP modifies their interaction with biological systems [5, 17,18,19]. The modification could lead to a new particle type, whose biological activity might be a combination of changed physicochemical properties and the toxicity of the bound substances
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