Persistence of silver nanoparticles in the rat lung: Influence of dose, size, and chemical composition

Abstract

Increasing silver nanoparticle (AgNP) use in sprays, consumer products, and medical devices has raised concerns about potential health effects. While previous studies have investigated AgNPs, most were limited to a single particle size or surface coating. In this study, we investigated the effect of size, surface coating, and dose on the persistence of silver in the lung following exposure to AgNP. Adult male rats were intratracheally instilled with four different AgNPs: 20 or 110 nm in size and coated with either citrate or polyvinylpyrrolidone (PVP) at 0.5 or 1.0 mg/kg doses. Silver retention was assessed in the lung at 1, 7, and 21 d post exposure. ICP-MS quantification demonstrated that citrate-coated AgNPs persisted in the lung to 21 d with retention greater than 90%, while PVP-coated AgNP had less than 30% retention. Localization of silver in lung tissue at 1 d post exposure demonstrated decreased silver in proximal airways exposed to 110 nm particles compared with 20 nm AgNPs. In terminal bronchioles 1 d post exposure, silver was localized to surface epithelium but was more prominent in the basement membrane at 7 d. Silver positive macrophages in bronchoalveolar lavage fluid decreased more quickly after exposure to particles coated with PVP. We conclude that PVP-coated AgNPs had less retention in the lung tissue over time and larger particles were more rapidly cleared from large airways than smaller particles. The 20 nm citrate particles showed the greatest effect, increasing lung macrophages even 21 d after exposure, and resulted in the greatest silver retention in lung tissue.

• Clearance
• intratracheal instillation
• macrophage
• respiratory

Acknowledgements

We are grateful to the following people for their skilled technical assistance during sample collection and processing: Ryan Mendoza, Imelda Espiritu, and Janice Peake. Imaging was conducted at the UC Davis Cellular and Molecular Imaging core. We thank the UC Davis Interdisciplinary Center for Inductively-Coupled Plasma Mass Spectrometry and both Peter Green and Joel Commisso for assistance with the ICP-MS samples and analysis. We thank the UC Davis Electron Microscopy Laboratory, Department of Medical Pathology and Laboratory Medicine, School of Medicine and Patricia Kysar for assistance with the macrophage TEM images.

Declaration of interest

The authors declare that they have no competing interests. Grant support (U01 ES020127) and silver nanomaterials used in this study are procured, characterized, and provided to investigators by the NIEHS Centers for Nanotechnology Health Implications Research (NCNHIR) Consortium. We acknowledge a Superfund Research Program Fellowship in support of Donald Anderson (P42 ES004699) and the Western Center for Agricultural Health and Safety (NIOSH Grant 0H07550) for Rona Silva. The NIEHS Centers for Nanotechnology Health Implications Research (NCNHIR) was established with the centers funded by RFA ES-09-011. These centers formed a consortium with other NIEHS funded researchers in the area of Nano EHS and worked together on a select set of engineered nanomaterials provided to the consortium by NIEHS. Any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the National Institute of Environmental Health Sciences or NIH.

Supplementary material available online

Supplementary Figures S1–S6 and Table 1