[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.