Photodynamic inactivation of planktonic and biofilm growing bacteria mediated by a meso-substituted porphyrin bearing four basic amino groups.

MAMONE L, FERREYRA DD, GÁNDARA L, DI VENOSA G, VALLECORSA P, SÁENZ D, CALVO G, BATLLE A, BUZZOLA F, DURANTINI EN, CASAS A

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2016

1011-1344

Biofilm-associated diseases account for 80% of all infections in humans. Due to the emergence ofantibiotic resistances, alternative therapies such as Photodynamic Inactivation (PDI) of microorganismshave emerged. Porphyrins with intrinsic positive charges have been proposed as successfulphotosensitizers (PSs) against microorganisms. We have recently designed the new synthetic porphyrin5,10,15,20-tetrakis[4-(3-N,Ndimethylammoniumpropoxy)phenyl]porphyrin (TAPP) containing fourbasic amine groups in the periphery of the tetrapyrrolic macrocycle, which can acquire positive chargesat physiological pH, thus favouring the interaction with biomembranes.Illumination of planktonic cultures of Staphylococcus aureus at 180 J/cm2 in the presence of 2.5 μMTAPP induced complete bacteria eradication.For the TAPP-PDI treatment of S. aureus biofilms, higher light fluences and PS concentrations wereneeded. Employing 20 µM TAPP and 180 J/cm2, around 3-log CFU reduction were obtained.In order to determine the efficacy of TAPP-PDI on Gram-negative bacteria, we performed planktonicand biofilm assays employing Pseudomonas aeruginosa. Much higher TAPP doses as compared to S.aureus were needed to achieve planktonic bacteria photosensitization (3-log CFU reduction at 20 µMTAPP and 180 J/cm2). On the other hand, high concentrations of TAPP were non toxic to P. aeruginosagrowing on biofilms, and employing 30 µM TAPP and 180 J/cm2 we obtained 3-log CFU reduction.The main conclusion of the present work is that TAPP is a promising and efficient PS capable ofpromoting photodynamic killing of both Gram -negative and -positive in planktonic bacteria, thoughmore effectively in the latter. In addition, TAPP-PDI induces similar photoinactivation rates in bothbacteria types growing on biofilms, with lower dark toxicity in the Gram-negative one.