Antimicrobial photodynamic inactivation of planktonic and biofilm cells by covalently immobilized porphyrin on polyethylene terephthalate surface

The appearance of resistant strains and the persistence of biofilms on different surfaces in a wide range of settings represent serious public health threats. Antimicrobial photodynamic inactivation (aPDI) is a promising alternative technology to overcome these challenges. The current study assessed the antimicrobial effect of polyethylene terephthalate (PET) discs covalently functionalized with a cationic porphyrin, against E. coli ATCC 25922 and Pseudomonas aeruginosa (Schroeter) Migula (ATCC (R) 10145TM) growth. Irradiation with white LED light for 6 h resulted in 1.51 +/- 0.03 and 3.26 +/- 0.24 log reduction of planktonic P. aeruginosa and E. coli, respectively. The study also assessed the effect of the functionalized discs on biofilm formation by E. coli, P. aeruginosa, and Staphylococcus aureus subsp. aureus (ATCC (R) 6538PTM). The biovolumes of S. aureus, P. aeruginosa, and E. coli biofilms were decreased by 0.6 +/- 0.1, 0.56 +/- 0.13 and 0.74 +/- 0.06 log reduction, respectively. These results emphasize the ability of porphyrin-functionalized photoactive surfaces to kill bacterial cells and consequently prevent biofilm formation.