Nanosilver induces minimal lung toxicity or inflammation in a subacute murine inhalation model

Abstract

BackgroundThere is increasing interest in the environmental and health consequences of silver nanoparticles as the use of this material becomes widespread. Although human exposure to nanosilver is increasing, only a few studies address possible toxic effect of inhaled nanosilver. The objective of this study was to determine whether very small commercially available nanosilver induces pulmonary toxicity in mice following inhalation exposure.ResultsIn this study, mice were exposed sub-acutely by inhalation to well-characterized nanosilver (3.3 mg/m3, 4 hours/day, 10 days, 5 ± 2 nm primary size). Toxicity was assessed by enumeration of total and differential cells, determination of total protein, lactate dehydrogenase activity and inflammatory cytokines in bronchoalveolar lavage fluid. Lungs were evaluated for histopathologic changes and the presence of silver. In contrast to published in vitro studies, minimal inflammatory response or toxicity was found following exposure to nanosilver in our in vivo study. The median retained dose of nanosilver in the lungs measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES) was 31 μg/g lung (dry weight) immediately after the final exposure, 10 μg/g following exposure and a 3-wk rest period and zero in sham-exposed controls. Dissolution studies showed that nanosilver did not dissolve in solutions mimicking the intracellular or extracellular milieu.ConclusionsMice exposed to nanosilver showed minimal pulmonary inflammation or cytotoxicity following sub-acute exposures. However, longer term exposures with higher lung burdens of nanosilver are needed to ensure that there are no chronic effects and to evaluate possible translocation to other organs.

Nanosilver – Harmful effects of biological activity

“…Nanosrebro -szkodliwe skutki działania Nr 6 833 rów, u myszy w tkankach, takich jak serce, wątroba i mózg, zawartość srebra była poniżej oznaczalności metody (7). Po narażeniu drogą pokarmową nanocząstki srebra mogą wchłaniać się z jelit do krwi i dalej do innych narządów.…”

“…Po 12-tygodniowej obserwacji od ustania narażenia ustalono wartość 117 mg/m 3 jako najwyższe stężenie, przy któ-rym nie obserwowano działania toksycznego (no observable adverse effect concentration -NOAEC), biorąc pod uwagę zmiany funkcjonowania płuc (podobne jak we wcześniejszych badaniach (22,6) A.M. Świdwińska-Gajewska, S. Czerczak Nr 6 836 U myszy narażanych inhalacyjnie na nanocząstki srebra (5 nm) przez 10 dni wykazano jedynie łagodny stan zapalny w płucach (7). Odnotowano statystycznie istotny wzrost całkowitej liczby komórek w popłuczy-nach oskrzelowo-pęcherzykowych (bronchoalveolar lavage fluid -BALF) oraz neutrofili, natomiast nie zaobserwowano różnic w aktywności dehydrogenazy mleczanowej (lactate dehydrogenase -LDH) i poziomu białka całkowitego między grupami (7). Efekty toksyczne w następstwie narażenia drogą oddechową zestawiono w tabeli 1.…”

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