Comparative photodynamic inactivation of bioluminescent E. coli by pyridinium and inverted pyridinium chlorins

Abstract

Photodynamic inactivation (PDI) is a therapeutic approach in study due to the ability to reduce or completely eliminate the bacterial strains without the development of resistance mechanisms. In this therapeutic methodology the cationic chlorins (Chls) with pyridinium or inverted pyridinium moieties are one of the photosensitizers exploited in our biological approaches. In this context, we synthesized and characterized new free-base and zinc(II) complexes of pyridinium or inverted pyridinium Chl derivatives (1b, 2, 2a and 2b, respectively) for the inactivation of Escherichia coli (E. coli). The PDI assay was performed with white light irradiation delivered at a fluence rate of 25 mW cm−2. The obtained results of this study demonstrate high PDI efficiency of the zinc(II) metallated Chl 1b, reaching the detection limit of the bioluminescent method (5.2 log reduction) in 45 min of irradiation.