Cationic Bacteriochlorin in the photodynamic inactivation of microorganisms

Bacteriochlorophyll extracted from groups of purple non-sulfur bacteria, structurally modified, produces the photosensitizer bacteriochlorin, used in photodynamic therapy (PDT). Photosensitizers (PS) irradiated with light of a specific wavelength provides the generation of reactive oxygen species through the excitation of molecular oxygen, leading to cell death. PDT is effective against bacterial and fungal infections and has the advantage of not developing bacterial resistance, unlike antibiotics. In this study, bacteriopheophorbide a methyl ester (Bchl-M) and a new cationic bacteriochlorin (Bchl-Cat) were produced from the extraction of bacteriochlorophyll from Rhodopseudomonas faecalis and used for photoinactivation studies. Bchl-Cat inactivated Staphylococcus aureus. For P. aeruginosa, inhibition reached approximately 3 logs at a concentration of 100 µM Bchl-Cat and a light dose of 45 J/cm². In E. coli, inhibition was approximately 4 logs at a concentration of 250 µM Bchl-Cat and a light dose of 45 J/cm². In Salmonella typhimurium, inhibition was 5 logs at a concentration of 250 µM Bchl-Cat and light doses of 20, 30 and 45 J/cm². For C. albicans, Bchl-Cat inhibited approximately 3 logs at a concentration of 250 µM and a light dose of 45 J/cm². Bchl-M was able to inhibit approximately 2 logs at a concentration of 250 µM and light doses of 20, 30 and 45 J/cm² of C. albicans. These results are significant and show that cationic photosensitizer is more effective in the inactivation of Gram-negative bacteria when compared to bacteriochlorin (Bchl-M).