Preparation of selenium nanoparticles by using silymarin and study of their cytotoxicity to tumor cells

The past few years have seen substantial progress in veterinary oncology: new methods have been developed for the diagnosis and treatment of oncological diseases in animals, and the range of possible therapeutic interventions has been broadened. Of interest, in particular, are the prospects for the creation of veterinary pharmaceuticals with the use of various nanoparticles, including colloidal selenium, on the surface of which are immobilized biologically active substances that have antitumor action. Selenium nanoparticles are cytotoxic to tumor cells and have also been considered as effective carriers for the in vivo targeted delivery of drugs, genetic materials, proteins, and so on. The well-tunable polyvalent structures of the selenium nanoparticle surface provide a convenient platform for integrating several therapeutic agents or biomacromolecules with covalent or noncovalent surface conjugation. We synthesized selenium nanoparticles in complex with silymarin, a flavonoid hepatoprotector extracted from the fruit of milk thistle [ Silybum marianum (L.) Gaertn.], and we evaluated the cytotoxicity of the resultant preparation to normal and tumorous cells. By using electron microscopy and dynamic light scattering, it was found that the developed procedure ensured the preparation of stable suspensions of silymarin-conjugated selenium nanoparticles with sizes ranging from 20 to 40 nm. The obtained conjugate was shown to be markedly cytotoxic to the Hep-2 tumor cell line, suppressing cell respiration approximately 6.5-fold as compared to the control, whereas the respiration of SPEV-2 normal cells was inhibited approximately 2.3-fold. Initial colloidal selenium had much weaker effects on both cell types, and pure silymarin had no statistically significant influence on SPEV-2 cells (in contrast to Hep-2 cells). The results of this study could be used in developing next-generation anticancer agents and are of interest in the implementation of green chemistry-based approaches.