Photodynamic effect of novel hexa-iodinated quinono-cyanine dye on Staphylococcus aureus.

BACKGROUND Staphylococcus aureus (S. aureus) is Gram-positive bacteria, a major human pathogen, which causes a wide variety of serious infections when it enters the bloodstream or internal tissues. Antimicrobial photodynamic therapy (APDT) utilizing a light-activated dye (photosensitizer) is a powerful method for in vitro and in vivo eradication of S. aureus and other pathogenic bacteria. However, the development of highly efficient, long-wavelength photosensitizers showing high phototoxicity to pathogens and low dark toxicity is still challenging. AIM To develop a highly efficient, long-wavelength photosensitizer for photodynamic inactivation of S. aureus. METHOD Synthesis of the new photosensitizer, hexa-iodinated quinono-cyanine dye IQCy and investigation of the dark and light-induced toxicity of this dye compared to known photosensitizers Chlorin e6 (Ce6) and HITC towards S. aureus. RESULTS When exposed to 14.9 J/cm2 white LED light, 0.5 µM of IQCy, Ce6 and HITC inactivate, respectively, 99 %, 40 % and 30 % of S. aureus and at 0.05 µM and 27.9 J/cm2 - 71 %, 18 % and 9%, which is much better compared to Ce6 and HITC. IQCy exhibits no dark toxicity at least at 10 µM dye concentration. CONCLUSIONS IQCy demonstrates a more pronounced photodynamic inactivation of S. aureus as compared to Ce6 and HITC and can be employed for the eradication of these bacteria at lower concentration and reduced light dose.