Ecotoxicological assessment of nanocrystalline cerium dioxide preparations

Abstract

Cerium is the most common rare earth metal and an element of industrial importance. Cerium dioxide (CeO2) is the best-known cerium compound, due to its unsurpassed redox properties and ability to guarantee excellent oxygen mobility. Upon conversion to a nanocrystalline state, the compound significantly alters its physicochemical properties, which determine the material’s unique biological activity. Recent literature reports the use of metal nanoparticles, especially cerium, as new natural feed additives in animal husbandry to increase productivity. However, there are still insufficient reports on the toxicodynamics and toxicokinetics of nanoparticles in humans and animals, as well as their environmental impact. Nanoparticles may have toxic effects because they can penetrate cells, bypass barriers such as the respiratory, dermal, gastrointestinal, blood-brain, and placental barriers, and selectively accumulate in cells and subcellular structures. The aim of the research was to determine the acute and chronic toxicity of nanodispersed cerium dioxide obtained by the employees of the Nanomedtech laboratory (Kyiv, Ukraine) and the Department of Interferon and Immunomodulators of the D.K. Zabolotny Institute of Microbiology and Virology. The results of the study of biochemical blood parameters showed that the research compound, after 10 days of daily administration, affected the functional state of the liver, as evidenced by impaired hepatocytes and a significant increase in transaminase activity and the mass coefficient of this organ. Hypertriacylglycerolemia, which is observed in organ lesions, also indicates impaired liver function. As a result of studying the toxic effects of NDC, administered daily to white rats for 10 days, it was found that the compound suppressed erythro- and leukocytopoietic functions of the hematopoietic organs, regardless of dose. It caused depletion, especially in the bone marrow, and reduced body reactivity, affecting the liver and spleen. Inflammatory processes, both acute and chronic, occurred under the compound’s influence. These compounds also affected some aspects of lipid metabolism and the liver’s functional state, possibly increasing the liver’s mass coefficient and the activities of ALT and AST.