Photodynamic Activity of Tribenzoporphyrazines with Bulky Periphery against Wound Bacteria

Abstract

Magnesium(II) tribenzoporphyrazines with phenoxybutylsulfanyl substituents were evaluated as photosensitizers in terms of their optical properties against wound bacteria. In the UV-vis spectra of analyzed tribenzoporphyrazines, typical absorption ranges were found. However, the emission properties were very weak, with fluorescence quantum yields in the range of only 0.002-0.051. What is important, they revealed moderate abilities to form singlet oxygen with the quantum yields up to 0.27. Under irradiation, the macrocycles decomposed via photobleaching mechanism with the quantum yields up to 8.64 × 10^-5. The photokilling potential of tribenzoporphyrazines was assessed against Streptococcus pyogenes, Staphylococcus epidermidis, as well as various strains of Staphylococcus aureus, including methicillin-sensitive and-resistant bacteria. Both evaluated photosensitizers revealed high photodynamic potential against studied bacteria (>3 logs). S.aureus growth was reduced by over 5.9 log, methicillin-resistant S. aureus by 5.1 log, S.epidermidis by over 5.7 log, and S. pyogenes by over 4.7 log.

Keywords: photodynamic antimicrobial therapy; porphyrazins; singlet oxygen; wound.

Figure 1

Chemical structures of studied macrocycles: MgPc, 1, and 2.

Figure 2

The UV-vis absorption spectra of studied macrocycles MgPc, 1, 2.

Figure 3

Chemical structures of previously studied macrocycles: sulfanylporphyrazine with isophthaloxybutyl substituents I, porphycene II, chlorin e6 III and phthalocyanine with quaternized morpholinethoxy substituents IV.

Figure 4

The UV-vis absorption and fluorescence spectra (excitation wavelength 325 and 600 nm) in DMF of 1 (a) and 2 (b).

Figure 5

The UV-vis absorption spectra in DMF of (a) DPBF decomposition during irradiation of the mixture of 1 and DPBF within 540 s; (b) photobleaching of MgPc within 600 s.