## 3 Results and Discussion
### Morphological Changes  
Treatment of HUVEC and MCF7 cells with concentrations less than 25 ug/mL of CoNiZn and CoNiFe NPs did not induce noticeable morphological alterations after 48 h. Exposure of HUVEC cells to 100 ug/mL of the prepared NPs for 48 h moderately decreased the cell viability without causing evident morphological changes. At the same time, the number of alive MCF7 cells treated with CoNiZn NPs was reduced, cells were shrunk, and apoptotic bodies were formed. In comparison with CoNiZn-treated MCF7 cells, CoNiFe-treated MCF7 cells were less affected. However, cell shrinkage, detachment of cells from culture plate, and formation of vacuolated cells were evident hallmarks of MCF7 cells treated with CoNiFe NPs at the given concentration (Figure 7). In the current study, CoNiFe and CoNiZn alloy NPs were synthesized by the polyol method and then characterized by XRD, SEM, and VSM analyses. Generally, because of the excellent magnetic and physical properties, such as superior corrosion resistance, low co  
Figure 5: Time- and concentration-dependent toxicity of CoNiFe NPs on Michigan Cancer Foundation-7 (MCF7) and human umbilical vascular endothelial cells (HUVECs) using MTT colorimetric assay following 24 and 48 h incubation. Data are expressed as mean \(\pm\) SD from one representative of three independent experiments. (**_p < 0.05_ compared with untreated cells). Figure 6: LDH leakage caused by CoNiZn and CoNiFe NPs following 48 h of exposure. Data are expressed as mean \(\pm\) SD from one representative of three independent experiments (**_p < 0.05_ compared with untreated cells). er activity, and high resistivity, the ternary alloys of CoNiFe are interesting materials for many high-added-value applications [30]; for example, [PERSON] et al. used nanocrystalline CoNiFe to protect stainless steel from a sodium chloride environment [31]. Recently, various types of superparamagnetic and ferromagnetic nanoparticles heated with alternating magnetic fields have been used in novel cancer therapies [32]. It was reported that the power loss in single-domain magnetic nanoparticles with a specific size range was significantly greater than that in multi-domain nanoparticles [33]. The CoNiFe NPs synthesized in this work, with the average crystalline size of 12.1 nm, showed the magnetic saturation M\({}_{8}\) = 94 emu/g. This sample can be fully saturated under the applied field because of its low coercive field (68.7 Oe). However, the spherical-shaped particles and the internal coupling interactions between the magnetic moments may influence the response to the applied alternating magnetic field [34]. Our in vitro cytotoxicity measurements revealed that CoNiZn and CoNiFe NPs induced time- and concentration-dependent toxicity and enhanced the LDH leakage in cancerous (MCF7) and non-cancerous (HUVEC) cell lines. However, unlike cancer cells, normal human cells were less affected during exposure to either CoNiZn or CoNiFe NPs. Nanotechnology has emerged as a novel field with potentially high research and clinical impact [35; 36]. In this respect, metallic alloy NPs have been introduced as a promising strategy to enhance therapeutic efficacy against cancer cells through enhancing the re-uptake, increasing reactive oxygen species production in cells, and, therefore, causing mitochondrial damage [37]. It has also been established that Au-Ag alloy NPs prepared via green synthesis could be applied as beneficial growth inhibitors for several biomedical applications [38]. Green synthesis of hollow CoPt alloy NPs has brought new insights in utilizing biocompatible NPs for theranostic applications [39]. [PERSON] et al.