Interplay of phosphate and carbonate ions with flavin photosensitizers in photodynamic inactivation of bacteria

by Daniel Bernhard Eckl, Stefanie Susanne Eben, Laura Schottenhaml, Anja Eichner, Rudolf Vasold, Andreas Sp äth, Wolfgang Bäumler, Harald Huber Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms v ia oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might h amper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated usingStaphylococcus aureus andPseudomonas aeruginosa as model organisms. Both were inactivatedin vitro at a low light exposure of 0.72 J cm-2. Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log10 steps of cell counts in low ion concentrations. Using the constant radiation ex...
Source: PLoS One - Category: Biomedical Science Authors: Source Type: research