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In this paper, a computer quantum-chemical simulation of the interaction of selenium nanoparticles with quaternary ammonium compounds was carried out, in which models of molecular complexes, electron density distribution, as well as higher populated and lower free molecular orbitals were obtained. For the presented molecular systems, the total energy of the molecular complex E, the difference in the energy of the quaternary ammonium compound molecule and the system «quaternary ammonium compound-selenium nanoparticles» ΔE, the energy of the highest occupied molecular orbital EHOMO, the energy of the lowest unoccupied molecular orbital ELUMO, and the chemical rigidity of the system η were calculated. As a result of data analysis, it was found that the interaction of selenium nanoparticles with quaternary ammonium compounds is energetically advantageous (ΔE > 11991 kcal/mol). The optimal system of interaction of selenium nanoparticles with quaternary ammonium compounds is the «cetyltrimethylammonium chloride-selenium nanoparticles» system, which is due to the highest value of the energy difference (ΔE = 11991,79 kcal/mol). Based on the analysis of the obtained models of molecular systems, it was found that when a quaternary ammonium compound interacts with selenium nanoparticles, the electron density is shifted and new molecular orbitals are formed, which indicate formation of a chemical interaction between the molecules. Next, IR spectroscopy of selenium nanoparticles stabilized with cetyltrimethylammonium chloride was performed. Based on the data obtained, it is found that there is a decrease in the intensity of the bands, in comparison with the IR spectrum of cetyltrimethylammonium chloride, in the regions from 2851 to 3026 cm-1 and from 1265 to 1377 cm-1, characteristic of the CH2 and CH3 groups, which indicates the presence of cetyltrimethylammonium chloride molecules oriented with the hydrophobic side to selenium particles on their surface. After that, the morphology of selenium particles was studied using the transmission electron microscopy method. As a result of the analysis of transmission electron microscopy images, the formation the layer of the quaternary ammonium compound on the surface of selenium particles with a diameter of 25 to 60 nm was confirmed.

Introduction. Due to the rapid development of nanotechnology, selenium nanoparticles (NPs) have recently attracted much attention due to their unique physical and chemical properties for biomedical applications, in particular for the treatment of oncological diseases. The review considers the selenium nanoparticles, which are widely studied in the field of oncology.Text. This review is devoted to the analysis of scientific literature on the anticancer activity of selenium nanoparticles against human cancer cell lines, as well as the application of these nanoparticles as a drug delivery system. Besides, the antitumor mechanisms of selenium nanoparticles against malignant neoplasms are discussed.Conclusion. According to the results of literary data analysis, it was found that selenium nanoparticles exhibit a good antitumor effect against various human cancer cell lines. It is shown that the antitumor activity of selenium nanoparticles is mainly related to activation of the extrinsic and intrinsic signaling pathways of apoptosis leading to cancer cell death. Also, selenium nanoparticles are promising systems for delivery of various anticancer drugs, providing high efficiency, bioavailability of drugs in tumor cells and minimizing toxicity to healthy cells.

This study examines the role of selenium and the effects of selenium nanoparticle-enriched food supplementation especially in ruminant animals. Selenium is an essential element that has multiple biological activities. Particularly it is important for many physiological processes, especially for the functions of reproductive and immune systems, metabolism of thyroid hormones, as well as antioxidant defense. Also, the presence of selenium nanoparticles in the diet provide a high content of selenium in milk and meat due to its high bioavailability and low toxicity, which is essential for humans.

Introduction. The prospects of using nanoparticles in the production of medicines are widely discussed in the literature. In 2018 alone, the quantity of registration certificates issued by national regulators for medicines that use nanoparticles in one form or another is around forty. Most of them are medicines based on liposomes, polymers, iron oxides, micelles. So far, no registration certificates have been issued for selenium nanoparticles. One of the reasons for this situation in this area, from our point of view, is that the mechanisms of interaction of nanoparticles with cells are not sufficiently studied. The lack of basic research in this area is one of the main obstacles to the development of new-generation drugs based on nanoparticles.Text. This review is devoted to the analysis of scientific data on the interaction of selenium nanoparticles with different types of cells. The article discusses the biological properties of selenium and its role in cell metabolism. Data on the cytotoxic effect of selenium nanoparticles on various cell cultures are presented. Methods of preparation of nanoparticles and methods for studying the interaction of nanoparticles with cell cultures are described.Conclusion. Analysis of the literature data allows us to draw conclusions about the relevance of research on the interaction of selenium nanoparticles with living cells. This is necessary to determine the mechanisms of selenium nanoparticles absorption, study their cytotoxic and / or cytostatic action, and distribution in cells. Investigation of the biological interaction of selenium nanoparticles with tumor and normal cells will determine the most informative methods for registering and quantifying their antitumor activity, which is relevant for the development of new drugs to treat cancer.