*3.9. In Vitro Cytotoxicity Assay*

The evaluation of cytotoxicity of antimicrobials is a critical step to guarantee their safe use. The results for the cytotoxicity of the newly synthesized dendrimers are shown in Figure 7. It has been found that both acridine dendrimer and its Cu-complex affected HEp-2 cells at similar doses, with CC50 values of 19.5 μg/mL and 19.4 μg/mL, respectively. At the active concentration of the [Cu2(ACR)(NO3)2]

against Gram-positive *B. cereus* (MIC 10 μg/mL) cell viability is near 75%, while other tests did not detect viable cells at the active concentrations of the dendrimers (MICs 40–120 μg/mL). The results also show that the binding of copper ions to the dendrimer molecule does not additionally increase the cytotoxicity of the dendrimer ligand ACR.

**Figure 7.** Cytotoxicity values of the compounds ACR (**A**), and [Cu2(ACR)(NO3)2] (**B**) towards HEp-2 cells.
