## 4 Discussion  
Glioblastomas represent more than 52% of all tumors that occur in the brain. Astrocytes are the source of glioblastomas. Glioblastoma is one of the lethal grade IV astrocytomas and has a mean survival rate of 15 months [30; 31]. Treatment of glioblastomas in the brain is complicated by the presence of physiological barriers in the brain, for example, the blood-brain barrier (BBB), the blood-cerebrospinal fluid barrier (BCSFB) and other barriers [32; 33]. The possibilities of using metal nanoparticles as carriers of anti-cancer drugs are being widely studied. Nanoparticles as carriers makes it possible to reduce the dose of therapeutic molecules and enhance their effect [10]. Selenium nanoparticles have shown their effectiveness in inducing apoptosis in cancer cells of various origins--breast cancer, prostate cancer, glioblastoma, hepatocellular carcinoma, etc. [25]. As for selenium nanorods, it is reported that biosynthesized SeNrs from Streptomyces bikinensis on the Hep-G2 and MCF-7 cell lines have an LD50 of 75.96 and 61.86 micrograms/mL\({}^{-1}\), respectively, which confirms the effectiveness in the treatment of cancer [34]. At the same time, the mechanism of action of selenium nanorods obtained by laser ablation is practically not studied. Despite the fact that these nanostructures are characterized by cheaper production and greater stability, this method of obtaining nanoparticles is characterized by the high purity of preparations. SeNrs showed a different dose anti-cancer efficacy, depending on the origin of the cancer cells. MCF-7 breast cancer cells have been found to be more sensitive to SeNrs compared to human hepatocellular carcinoma HepG2 cells [35]. Similarly, spherical selenium nanoparticles have shown more pronounced anti-cancer effects on HepG2, MCF-7 cells compared to CaCo-2 colorectal cancer cells or human glioblastoma [25; 29; 36]. In the present work, it was found that SeNrs more effectively induce apoptosis in glioblastoma A-172 cells compared to spherical SeNPs. Induction of apoptosis in A-172 cells occurred as early as 24 h after incubation with SeNrs, while under the action of SeNPs such effects could be achieved after 48 h of exposure. At the same time, after a 48-h exposure to SeNPs, inflammatory processes were also recorded in A-172 cells, which was not observed after SeNrs. A number of studies show the absence or mild cytotoxic effects of selenium nanostructures on \"healthy\" cells and tissues [29; 37; 38]. It has been shown that inorganic forms of selenium increase the activity of glutathione peroxidase in healthy cells, but selectively destroy their mitochondria through the release of free radicals in cancer cells. Thus, selenium is able to exert a selective anti-cancer effect [39; 40]. In addition, our experiments showed that both types of nanoparticles were effective regulators of selenium-containing protein expression. A particularly important fact is the increase in the expression of SELENOT and SELENOT genes in glioblastoma cells after exposure to SeNPs and SeNrs, but the effects of SeNrs were more pronounced. These selenoproteins are of great importance in the regulation of the functions of the endoplasmic reticulum and are associated with carcinogenesis [41]. Similarly, spherical SeNPs did not generate Ca\({}^{2+}\) signals in healthy L-929 mouse fibroblasts. However, in this case, SeNrs resulted in a slow increase in [Ca\({}^{2+}\)]i in fibroblasts, which indicates a lower selectivity of nanoparticles of this form to cells. As for selenoproteins, the studied nanoparticles also had almost no effect on, or regulated to a significantly lesser extent, the expression of most selenoprotein genes in fibroblasts of the L-929 line. Selenium nanoparticles are used to enhance the effectiveness of radiotherapy, when the application of SeNPs together with irradiation enhances ROS production [42], ER-stress and leads to apoptosis induction in cancer cells and mitochondrial dysfunction [43].