In vitro antibacterial photodynamic action on nosocomial S. aureus using porphyrins as photosensitizers

The antibacterial photodynamic therapy (aPDT) exerted by porphyrins has been ascribed for the production of singlet oxygen species. This research paper evaluates the singlet oxygen production capacity and photodynamic efficacy of two neutral porphyrins namely, meso-5,10,15,20-tetrakis(4-hydroxylphenyl)porphyrin (m-THPP), meso-5,10,15,20-tetrakis(3-pyridyl)porphyrin (m-T3-PyP) and one cationic meso-5,10,15,20-tetrakis(N-methylpyridinium-3-yl)porphyrin tetra-iodide (m-T-3Py⁺P4I^-) on nosocomial Staphylococcus aureus (ATCC #25923) strain. Absorption, emission and excitation spectra were utilised to estimate the singlet oxygen quantum yields, (φ∆), of the porphyrins. The singlet oxygen yields of the porphyrins were in 0.005 and 0.15 range and are considered adequate for the photoinactivation of bacteria. The antibacterial photodynamic therapy experiment revealed that the Staphylococcus aureus colonies were totally eliminated at a concentration of 2.50 mg/mL under light emitting diodes blue light of 470 nm wavelength for 60 minutes. This investigation further upholds the perception of aPDT as an auspicious substitute for treating antibiotic-resistant bacterial infections.