**4. Conclusions**

For the first time, acridine has been used for the modification of a poly(propylene imine) dendrimer (ACR). The new fluorescent dendrimer has been used as a ligand to obtained its Cu(II) complex [Cu2(ACR)(NO3)2]. EPR, FTIR, and fluorescent spectroscopy have been used to confirm the structure of metallodendrimer. It has been found that two copper ions are included in the dendrimer core by coordination with the inner tertiary nitrogen atoms. The basic photophysical characteristics of dendrimer have been examined in different organic solvents, and a negative fluorescence solvatochromism has been observed. The antimicrobial activity of dendrimers has been tested in vitro against some model Gram positive and Gram negative bacteria and yeasts. The results demonstrated enhancement in the antimicrobial activity of acridine dendrimer via complexation with copper ions against *B. cereus* and *C. lipolytica*. Deposition of dendrimers on the surface of cotton fabric has led to an increase in hydrophobicity of the textile. That prevents the formation of bacterial biofilm and makes these compounds useful for the production of antibacterial cotton fabrics.

**Author Contributions:** Conceptualization, P.B. and I.G.; methodology, synthesis, characterization and supervision P.B. and I.G.; textile investigation, D.S.; microbiological E.V.-T.; cytotoxicity assay P.G. and I.N.; EPR analysis R.K. and R.S.; project administration I.G. and P.B.

**Funding:** This research was funded by Fund "Scientific Research", Ministry of Education and Science of Bulgaria, grant number КОCТ01/24-2017" and "Ministry of Economy and Competitively of Spain", grand number RTI2018-096328-B-I00

**Acknowledgments:** IG and PB acknowledge COST CA15114 action "Anti-MIcrobial Coating Innovations to prevent infectious diseases (AMICI)".

**Conflicts of Interest:** The authors declare no conflict of interest.
