Photophysical properties and photodynamic efficiency of cationic porphyrins

Abstract

Photodynamic inactivation of some microorganisms (St. aureus, E.coli) was investigated and their dependence on photo-physical properties of photosensitizers (PS) (cationic porphyrins and metalloporphyrins) was shown. One of the most important criteria for the effectiveness of the PS`s is the quantum yield of singlet oxygen (γ ∆ ). Our investigations were shown that γ ∆ of metalloporphyrins, containing Zn, significantly higher than of metal-free porphyrins (85-97% and 77-79%, respectively). Previousl y experimentally we were found that under the action cationic porphyrins and metalloporphyrins on Gram (+) and Gram (-) microorganisms efficiency of metalloporphyrins Zn-TOEt4PyP and Zn-TBut4PyP in 3-5 times was higher than the metal-free porphyrins. In this study under the action of porphyrins and their Zn-derivatives on microorganism St. aureus such an effect was confirmed. Using the LED with a peak emission of 405 nm and a power density of 70 mW/cm 2 , and irradiation time of microorganisms from 5 to 30 minutes we have found, that at a concentration of 0.1 ug/ml the highest efficiency is observed of metalloporphyrin Zn-TBut3PyP. Upon irradiation of 10 and 15 min his efficiency is 3-5 times higher than the metal-free porphyrin TOEt4PyP, and irradiation for 30 min via Zn-TBut3PyP is practically completely kills microorganisms. These data correlate with the quantum yield of singlet oxygen for photosensitizers. The 30 mindirect sun exposure (power density of 70 mW/cm 2 ) of photosensitizer solutions showed that a significant photobleaching of porphyrins and metalloporphyrins does not occur. Thus, Zn-containing cationic metalloporphyrins are highly efficient photosensitizers for photodynamic inactivation of microorganisms and PDT.

Photophysical and Bactericidal Properties of Pyridinium and Imidazolium Porphyrins for Photodynamic Antimicrobial Chemotherapy

“…Nevertheless, it has been shown that cationic PS exhibited a good affinity for bacteria by interacting through electrostatic interactions, with the highly negatively charged cell wall components such as lipoteichoic acid (LTA) and lipopolysaccharide (LPS) in Gram-positive and Gram-negative bacteria, respectively [ 15 , 16 , 17 ]. Accordingly, cationic porphyrins displayed photoinduced activity against a broad spectrum of bacteria [ 17 , 18 , 19 , 20 ], and this trend was also confirmed with several families of cationic PSs [ 21 , 22 , 23 ].…”