g., trifluoromethyl groups), the introduction of aromatic hydrocarbon side groups and the modulation of the number PF-6463922 molecular weight of positive charges on the PS [8, 21, 24, 26–29]. This increase in the amphiphilic character of the PS seems to enhance its affinity for bacteria which improves its accumulation in the cells [25, 27] and is accompanied by an increase in the photocytotoxic activity [24]. The aim of this study was to compare the efficiency of seven cationic porphyrins differing in meso-substituent groups, charge number and charge distribution, on the photodynamic inactivation of a Gram (+) bacterium (Enterococcus faecalis) and a Gram (-) bacterium (Escherichia coli). The choice
of these porphyrins was based GS-9973 solubility dmso on the following facts: positive charges are required when the aim is to photoinactivate both Gram bacteria; these porphyrins are functionalized with groups that allow further immobilization on solid matrixes; previous studies performed in our laboratory showed that some of the selected porphyrins are efficient PS against other microorganisms
such as sewage bacteriophage [30], bacterial endospores [31], sewage faecal coliforms [7] and recombinant bioluminescent E. coli [32]. The present study complements our previous work on the search for PS to be considered as good candidates for the photoinactivation of a large spectrum of environmental microorganisms. The tetracationic porphyrin (Tetra-Py+-Me), extensively studied in bacterial and viral PI, was tested making it possible to evaluate the efficiency of the photodynamic process. Results We have tested the photocytotoxiCity Nintedanib (BIBF 1120) of seven meso-substituted cationic
porphyrin derivatives (Fig. 1) differing in meso-substituent groups, charge number and charge distribution against E. coli and E. faecalis. All the new porphyrins were fully characterized by spectroscopic data and showed UV-Vis spectra of “”Etio”" type, typical of this type of derivatives. The efficiency of the PS was evaluated based on the determination of the number of viable colony forming units (CFU) per millilitre. Figure 1 Cationic porphyrin derivatives. Structure of the seven cationic porphyrin derivatives used for photoinactivation of E. faecalis and E. coli. Photodynamic inactivation of bacterial cells The results of light and dark controls (Figs. 2, 3, 4, 5, 6, 7 and 
showed that the viability of E. coli and E. faecalis is neither affected by irradiation itself (light control) nor by any of the PS tested in the dark (dark control) using the highest concentration studied (5.0 μM). In these controls ~7.2 log CFU mL-1 is maintained during all experimental period. This indicates that the reduction obtained in cell viability after irradiation of the treated samples is due to the photosensitizing effect of the porphyrin. Figure 2 Bacterial photoinactivation with check details Tri-Py + -Me-PF. Survival curves of E.