Efficient Photodynamic Inactivation of Escherichia coli using a Zinc(II)-Bisdipicolylamine Complex Bearing Porphyrin Derivative and its Liposomal Formulation

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Selvi H. T. , Şahin S., Akbulut D., Türkyilmaz S.

9th International Drug Chemistry Congress, Antalya, Turkey, 8 - 11 April 2021, pp.61

  • Publication Type: Conference Paper / Summary Text
  • City: Antalya
  • Country: Turkey
  • Page Numbers: pp.61


Antibiotic resistant bacterial strains (e.g. MRSA, VRE, MDR-TB and so on) pose a significant threat to public health1 and complete drug resistance could prove to be more lethal than viral pandemics like Covid-19.2 Targeted antibacterial agents may improve antibiotic efficacy compared to non-targeted agents by widening their therapeutic window.  While a number of bacterial recognition motifs exist (e.g. antibodies, peptides, glycodendrimers, and cationic dendrimers), zinc(II)-bisdipicolylamine (Zn2BDPA) complexes are noteworthy as broad-spectrum bacterial targeting groups that selectively bind to negatively charged phosphate amphiphiles displayed on the outer surfaces of bacterial cell membranes and walls (Figure 1, Panel A).3a-d 

In this study we have prepared and investigated the antibacterial photodynamic inactivation (PDI) efficacy of Zn2BDPA bearing porphyrin derivative 1a (Figure 1, Panel B). 1a was synthesized from the corresponding aminoporphyrin derivative and a BDPA-ligand bearing carboxylic acid. The identity of 1a was confirmed through structural (NMR, HRMS) and photophysical (UV-Vis, FL) characterization. In a previous study we determined that upon irradiation with visible light ( > 400 nm) the iodo derivative 1b was capable of eradicating 99.99% of E. coli cells (5x106 CFU/ml) at 2.5 M concentration. In this study we have observed that trifluoromethyl derivative 1a eradicated 99.99% of E. coli cells (5x106 CFU/ml) at 0.25 M concentration upon irradiation with visible light. We have also discovered that it is possible to integrate 1a in a POPC/cholesterol host membrane. A liposomal formulation of 1a was thus prepared and characterized through DLS and zeta potential measurements. Liposomal 1a was found to be a highly efficient PDI agent as well, eradicating 99.99% of E. coli cells (5x106 CFU/ml) at 0.125 M effective porphyrin derivative concentration upon irradiation with visible light.

Acknowledgement: We gratefully acknowledge partial support for this work from TÜBİTAK (215Z052, 114C041), Istanbul University (53435, 45772), and Middle East Technical University (2667).


1) www.ft.com/content/520b0300-1717-4f66-b792-f2f7da7112a3 (accessed 15.03.2021)

2) news-decoder.com/without-antibiotics-more-could-die-than-from-covid-19/ (accessed 15.03.2021)

3) a. Turkyilmaz, S.; Rice, D.R.; Palumbo, R.; Smith B.D. Org. Biomol. Chem. 2014, 12, 5645-5655; b. Rice, D.; Plaunt, A. J.; Turkyilmaz, S.; Smith, M.; Wang, Y.; Rusckowski, M.; Smith B.D. Mol. Imaging Biol. 2015, 17, 204-213; c. Xiao, S.; Turkyilmaz, S.; Smith, B.D. Tetrahedron Lett. 2013, 54, 861-864; d. Xiao, S.; Abu-Esba, L.; Turkyilmaz, S.; White, A.G.; Smith B.D. Theranostics 2013, 3 (9), 658-666.