Unmodified PAMAM dendrimers have a high transfection efficiency, reaching about 80%, which unfortunately comes at the cost of their very high toxicity. In the case of (CuSO4)18@DAB-dendr-(Pyrr)64 tested in this study, at its non-toxic concentration (3.5 µM), the transfection efficiency of 82.55% was achieved after 48 hours of incubation with the vehicle, which shows that it can successfully replace the commercially used lipofectamine, which in the same conditions, at the concentrations proposed by the manufacturer, shows significant cytotoxicity to the THP1 cells. For the same reason, the (ZnCl2)22@DAB-dendr-(Pyrr)64 dendrimer cannot be dispensed with as an siRNA carrier. Perhaps its transfection efficiency in THP1 cell line after 72 hours was only 58% compared to more than 90% of lipofectamine, but with an incomparably lower toxicity of the (ZnCl2)22@DAB-dendr-(Pyrr)64 The present study investigated the cytotoxicity and complexing ability of two ion-modified PAMAM-pyrr dendrimers to determine the optimal conditions for their use as gene transfection agents. Eg5 was selected as a molecular target as a member of the kinesin family involved in various mitotic processes such as spindle assembly, chromosome positioning, mitotic centrosome separation and bipolar spindle formation. Overexpression of Eg5 has been observed in lung adenocarcinoma , renal cell carcinoma , hepatocellular carcinoma , pancreatic adenocarcinoma and cervical adenocarcinoma and is believed to be essential for the survival of cancer cells. Moreover, it has been shown that overexpression of Eg5 is correlated with poor clinical prognosis in patients with the above-mentioned cancers. Since silencing Eg5 leads to cell cycle arrest during mitosis, resulting in cell death, it may be a promising molecular target in cancer treatment. This study confirmed that the (CuSO4)18@DAB-dendr-(Pyrr)64 dendrimer is a better carrier of genetic material than the commercial compound because it is less toxic than lipofectamine, has higher transfection efficiency already after 48 hours, effectively delivers functional siRNA to acute monocytic leukemia (THP1) cells and silences expression a selected molecular target at the RNA level.