In vitro exposure of a 3D-tetraculture representative for the alveolar barrier at the air-liquid interface to silver particles and nanowires

April 2, 2019

Ionel Fizeșan1, Sébastien Cambier2, Elisa Moschini2, Aline Chary2, Inge Nelissen3, Johanna Ziebel2, Jean-Nicolas Audinot4, Tom Wirtz4, Marcin Kruszewski5,6, Anca Pop1, Béla Kiss1, Tommaso Serchi2, Felicia Loghin1 and Arno C. Gutleb2

1Toxicology Department, Faculty of Pharmacy, Iuliu Hațieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania. 
2Environmental Research and Innovation (ERIN) Department, Luxembourg Institute of Science and Technology, Belvaux, Luxembourg. 
3Health Unit, Flemish Institute for Technological Research (VITO NV), Mol, Belgium. 
4Material Research and Technology (MRT) Department, Luxembourg Institute of Science and Technology, Belvaux, Luxembourg. 
5Faculty of Medicine, University of Information Technology and Management in Rzeszow, Sucharskiego 2, Rzeszow, Poland. 
6Centre for Radiobiology and Biological Dosimetry, Institute of Nuclear Chemistry and Technology, Dorodna 16, Warszawa, Poland


This study aimed to investigate the distinctive biological effects elicited by two different sizes of spherical silver particles (Ag20 and Ag200) and of PVP-coated silver nanowires (AgNWs) in a 3D tetra-culture in vitro model, representative for the alveolar barrier using the Vitrocell™Cloud System. The second objective was to investigate the influence of the AgNMs shape on biological responses. Only a few scientific articles studied the biological effects of AgNWs, and to the best of our knowledge, none investigated the biological effects using an ALI system.


Background: The present study aimed to evaluate the potential differences in the biological effects of two types of spherical silver particles of 20 and 200 nm (Ag20 and Ag200), and of PVP-coated silver nanowires (AgNWs) with a diameter of 50 nm and length up to 50 μm, using a complex 3D model representative for the alveolar barrier cultured at air-liquid interface (ALI). The alveolar model was exposed to 0.05, 0.5 and 5 μg/cm2 of test compounds at ALI using a state-of-the-art exposure system (Vitrocell™Cloud System). Endpoints related to the oxidative stress induction, antioxidant defence mechanisms, pro-inflammatory responses and cellular death were selected to evaluate the biocompatibility of silver particles and nanowires (AgNMs) and to further ascribe particular biological effects to the different morphologic properties between the three types of AgNMs evaluated.
Results: Significant cytotoxic effect was observed for all three types of AgNMs at the highest tested doses. The increased mRNA levels of the pro-apoptotic gene CASP7 suggests that apoptosis may occur after exposure to AgNWs. All three types of AgNMs increased the mRNA level of the anti-oxidant enzyme HMOX-1 and of the metalbinding anti-oxidant metallothioneins (MTs), with AgNWs being the most potent inducer. Even though all types of AgNMs induced the nuclear translocation of NF-kB, only AgNWs increased the mRNA level of pro-inflammatory mediators. The pro-inflammatory response elicited by AgNWs was further confirmed by the increased secretion of the 10 evaluated interleukins.
Conclusion: In the current study, we demonstrated that the direct exposure of a complex tetra-culture alveolar model to different types of AgNMs at ALI induces shape- and size-specific biological responses. From the three AgNMs tested, AgNWs were the most potent in inducing biological alterations. Starting from 50 ng/cm2, a dose representative for an acute exposure in a high exposure occupational setting, AgNWs induced prominent changes indicative for a pro-inflammatory response. Even though the acute responses towards a dose representative for a full-lifetime exposure were also evaluated, chronic exposure scenarios at low dose are still unquestionably needed to reveal the human health impact of AgNMs during realistic conditions.

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