[Toxicological evaluation of nanosized colloidal silver, stabilized with polyvinylpyrrolidone, in 92-day experiment on rats. II. Internal organs morphology].

The aim of the study was to evaluate the safe doses of commercially available nanosized colloidal silver (NCS), stabilized with polyvinilpirrolidone (PVP, food additive E1201) when administered in gastrointestinal tract of rats in the 92-day experiment in terms of the morphological changes in the internals of animals. The sample studied contained non-aggregated nanoparticles (NPs) of silver belonging to size fractions with a diameter of less than 5 nm, 10-20 nm or 50-80 nm. 80% of NPs were inside the range of hydrodynamic diameters 10.6-61.8 nm. The preparation of NCS was administered to growing male Wistar rats. (initial body weight 80 ± 10 g) for 1 month by intragastric gavage and then consumed with food at doses of 0.1, 1.0 and 10 mg/kg of body weight based on silver. The control animals received water or vehicle of nanomaterial--water solution of PVP. After withdrawal of animals from the experiment by exsanguination under ether anesthesia organs (liver, spleen, kidney, ileum) were isolated and their slides were prepared by standard methods following 'by staining with hematoxylin-eosin. Analysis was performed in light optical microscope equipped with a digital camera at a magnification from 1 x 100 to 1 x 1000. It was shown that the experimental animals treated with the NCS developed series of morphological changes in the tissues of the internal organs (liver, spleen and kidney) with the elevation of the range and severity of structural changes with increasing doses of silver. The most sensitive target of NCS action was apparently liver, which has already shown at a dose of 0.1 mg of silver NP/kg of body weight marked eosinophilic infiltration of portal tracts, which was accompanied at doses of 1.0 and 10.0 mg/kg by the emergence of medium and large-drop fat vacuoles in the cytoplasm of hepatocytes, swelling and lympho-macrophage. infiltration of the portal tracts. Detectable changes can be regarded as symptoms of inflammation of hepatocytes, at least, at a dose nanomaterial of 1.0 mg/kg body weight or more. Relative intensity of morphological changes in the internal organs correlated with published data on the biodistribution of silver NP administered to the gastrointestinal tract. It is concluded that the threshold dose corresponding to the minimum adverse effect of NCS is, according to the study of the above, no more than 1.0 mg/kg of body weight based on silver.

[Toxicological assessment of nanostructured silica. The acute oral toxicity].

Nanostructured amorphous silica (SiO2) is one of the priorities of nanomaterials, exposing human to the ever-increasing scale as a component of food additives, drugs and cosmetic products. According to numerous publications SiO2 nanoparticles (NPs) possess deleterious effects on animal and human cells in vitro and also exhibit inhalation toxicity. However, the biological effects in vivo of silica NPs taken orally are studied insufficiently. This article represents the first section of this study which aim is identification of silica preparation as nanomaterial and estimating of acute toxicity after oral administration in the form of aqueous suspension. Studies of size and shape of the particles in aqueous suspension of silica used in the study by electron and atomic force microscopy, spectroaqustic analysis and dynamic laser light scattering showed that the test substance is a nanomaterial. Estimation of acute toxicity of an aqueous suspension of nanostructured silica with a single intragastric gavage to male BALB/C mice allowed to conclude that the test material has LD50 by the oral route greater than 10 000 mg/kg and consequently belongs to class IV (low danger agents). Pathological changes in jejunum and colon of mice in the acute experiment (at a dose of 10 000 mg/kg) haven't been identified. Thus SiO2 NPs possess low toxicity when administered in the gastrointestinal tract. The available data, however, do not exclude possible presence of adverse effects under their long-term administration by oral way.