Evolution of Silver Nanoparticles in the Rat Lung Investigated by X-ray Absorption Spectroscopy

Abstract

Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurements taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. We found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.

Size-Dependent Deposition, Translocation, and Microglial Activation of Inhaled Silver Nanoparticles in the Rodent Nose and Brain

“…Particle size can also contribute to dissolution, with smaller citrate-coated C20 undergoing faster dissolution than larger C110 (Wang et al 2014; Zhang et al 2011). Whereas C20 may immediately dissolve to form Ag + and, in subsequent ionic reactions, form smaller AgNP, C110 sheds continuously, as evidenced by concurrent high concentrations of Ag + around the parent AgNP over time (Davidson et al 2015). C20 could be rapidly transported to the OB with the highest deposition occurring at the earliest time point (T0).…”

“…C20 could be rapidly transported to the OB with the highest deposition occurring at the earliest time point (T0). In contrast, owing to a slower dissolution process, C110 may not reach the OB until approximately 21 days after exposure because C110 produces more Ag + ions that continuously go through cycles of small-particle formation and dissolution until the parent AgNP are depleted (Davidson et al 2015). Thus, the time for transport and accumulation of C110 Ag in the OB is extended.…”

“…The toxicity of Ag + may be due to its interaction in biochemical processes with proteins, nucleic acids, and cell membranes (Chernousova and Epple 2013). Smaller (20 nm) AgNP were found to have faster dissolution rates and Ag + formation than larger (110 nm) AgNP (Davidson et al 2015; Wang et al 2014). …”

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

“…Collaborative research by Davidson and colleagues (2015) has been performed to better understand the dominant silver species in lung tissues upon inhalation of C20 and C110. X-ray absorption spectroscopy was performed at 0, 1, 3, and 7 days post-inhalation.…”

Silver nanoparticles: Electron transfer, reactive oxygen species, oxidative stress, beneficial and toxicological effects. Mini review

“…AgNPs are widely used in industry, mainly as an antibacterial agent, which this has led to more direct and indirect exposure in humans. Pulmonary and lung‐related exposure to AgNPs can occur by air pollution in NP manufacturing sites, or via inhalation of water droplets containing AgNPs (Davidson, Anderson, Van Winkle, Pinkerton, & Guo, ). AgNPs in fine mist form are being explored for potential inhalation therapy for respiratory infections and allergic airways inflammation (Davidson, Anderson, Van Winkle, Pinkerton, & Guo, ).…”