Toxicity of nanosilver in intragastric studies: Biodistribution and metabolic effects

• Acute and sub-acute intragastric administrations of AgNPs do not result in rats’ lethality or pronounced toxic effects.
• Hematological and biochemical parameters do not change after rats’ exposure to AgNPs.
• Silver absorbs from the gastrointestinal tract and distributes to various secondary organs.
• The liver and kidneys are the major target organs for AgNPs.
• Silver is efficiently excreted from rats.

The unique physicochemical properties of silver nanoparticles explain their extensive application in consumer goods, food, and medicinal products. However, the biological effects of nanosilver after peroral exposure of mammals are still debatable. This study describes the biodistribution and biological action of 12 nm non-coated silver nanoparticles intragastrically administered to male rats after acute (single exposure) and sub-acute (multiple exposures over 30 days) toxicity experiments. The daily doses were 2000 and 250 mg/kg of body weight for single and multiple administrations, respectively. Silver tissue detection was conducted by elemental analysis with the help of atomic absorption spectroscopy. An estimation of the state of exposed animals was made and the dynamics of hematological and biochemical parameters of rats was studied. It was demonstrated that single and multiple administrations resulted in silver accumulation in the liver, kidneys, spleen, stomach, and small intestine. After both one- and repeated-dose exposures, the highest Ag contents were detected in the liver (0.87 ± 0.37 μg/g of organ) and kidneys (0.24 ± 0.02 μg/g of organ). The concentrations of silver detected in tissues were far smaller than the administered doses (<99%), indicating its efficient excretion from the organism. Acute and sub-acute exposures caused no animal mortality or signs of toxicity, manifested as changes in outward appearance or notable deviations in behavior or locomotor activity. Postmortem study revealed no visible pathomorphological abnormalities of internal organs. Hematological indices and biochemical parameters of the treated rats did not differ from those of the vehicle control animals. Overall, it can be concluded that nanosilver is able to be absorbed from the gastrointestinal tract into the bloodstream and accumulate in the secondary organs of rats. It showed no distinct toxicity under the experimental conditions of this study.

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