Comparison of two different application routes of nanosilver in rats – A toxicokinetic study

Owing to their antimicrobial properties, silver nanoparticles are the most commonly used nanoparticles. The constantly increasing use of silver nanoparticles in products related to food and food contact materials is the reason why oral administration of nanoparticles is considered as an important uptake route and should be studied. Therefore, the tissue distribution and excretion of coated silver nanoparticles was investigated in rats after single oral administration including a 7-days post treatment observation time. The animals received silver nanoparticles at a dose of 20 mg/kg body weight and an equimolar dose of silver ions by gavage. The silver content was measured in different organs after days 1, 2, 3 and 7. To assess the effect of the intestinal passage on systemic bioavailability an additional group of rats was intravenously administered with 4 mg/kg body weight silver nanoparticles and a group was treated with an equimolar dose of silver ions. The accumulation of silver was compared after 24 h single intravenous administration. So far, the accumulation of silver was observed in different organs. As expected, most of the nanosilver was excreted via feces and minor amounts were detected in intestine and colon. Orally administered ionic silver was detected in feces and additionally in the urine. Remarkably, also after intravenous injection of nanosilver silver was found in feces, which suggests biliary excretion of silver nanoparticles. It is concluded that the oral resorption of nanosilver results in an accumulation of silver in different organs and feces and the intravenous application suggests a biliary excretion.