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 110nm in size and coated with either citrate or polyvinylpyrrolidone (PVP) at 0.5 or 1.0mg/kg doses. Silver retention was assessed in the lung at 1, 7 and 21 days post exposure. ICP-MS quantification demonstrated that citrate coated AgNPs persisted in the lung to 21 days with greater than 90% retention, while PVP coated AgNP had less than 30% retention. Localization of silver in lung tissue at one day post exposure demonstrated decreased silver in proximal airways exposed to 110nm particles compared with 20nm AgNPs. In terminal bronchioles one day post exposure, silver was localized to surface epithelium but was more prominent in the basement membrane at 7 days. 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 20nm citrate particles the greatest effect; increasing lung macrophages even 21days after exposure and resulted in the greatest silver retention in lung tissue.

Particle coatings but not silver ions mediate genotoxicity of ingested silver nanoparticles in a mouse model

“…The polydispersity index, a measure of the variance in mean hydrodynamic diameter measurements, was 0.15 ± 0.01 for citrate-coated AgNPs and 0.2 ± 0.01 for PVP-coated AgNPs. These analyses indicated AgNPs of the expected size and a narrow size distribution, consistent with other studies using the same AgNPs (Anderson et al, 2015; Wang et al, 2014). …”

“…Likewise, Ag levels were not significantly different in the lungs of rats at 1 day after intratracheal instillation of citrate- and PVP-coated AgNPs (Anderson et al, 2015). However, Ag levels at 21 days post-exposure were 3-fold higher in rats exposed to citrate-coated AgNPs than PVP-coated AgNPs (Anderson et al, 2015). This observation suggested that citrate-coated AgNPs persist in the lung longer than PVP-coated AgNPs.…”

“…Anderson et al. reported that in rats exposed to AgNPs by intratracheal instillation, citrate-coated AgNPs resulted in a greater Ag retention in the lungs and a greater increase in lung macrophages at 21 days post-exposure compared to PVP-coated AgNPs (Anderson et al, 2015). Bergin et al.…”

Aerosolized Silver Nanoparticles in the Rat Lung and Pulmonary Responses over Time

“…In their study, citrate-coated Ag NPs produced greater and/or longer-lasting effects than PVP-coated ones due to a greater ability of PVP-coated Ag NPs to complex released Ag cations (Ag + ). Previous studies by our group, Anderson and colleagues (2014), using the same materials showed greater clearance of instilled PVP- versus citrate-coated Ag NPs. In accordance with findings by oropharyngeal aspiration (Wang et al , 2013), we hypothesized that nose-only inhalation of C20 would produce greater acute cellular toxicity and neutrophilic inflammation than C110 and that C110 would produce mild sub-chronic pulmonary fibrosis.…”

“…Primary size and morphology, hydrodynamic size and electrostatic potential, elemental and Ag + composition, and endotoxin content were determined using transmission electron microscopy (TEM), dynamic light scattering (DLS), inductively coupled plasma mass spectrometry (ICP-MS), and the Kinetic Turbidity and Gel-clot limulus amebocyte lysate (LAL) assays, respectively. Descriptions and results of these characterization methods have been presented previously (Wang et al , 2013, Anderson et al , 2014). …”