The application of antimicrobial photodynamic therapy on S. aureus and E. coli using porphyrin photosensitizers bound to cyclodextrin

Photodynamic therapy is usually used against malignant and non-malignant tumors. Nowadays, due to resistance of bacterial strains, we are looking for a new antimicrobial strategy to destroy bacteria with minimal invasive consequences. The worldwide increase in antibiotic resistance among different classes of gram-positive and gram-negative bacteria has led to the search for alternative anti-microbial therapies such as antimicrobial PDT (aPDT). Development antimicrobial technology combines a nontoxic compound, called photosensitizer, visible light of the appropriate wavelength, and the generation of reactive oxygen species. In this work, the photosensitizers TMPyP and ZnTPPS4 are investigated for photodynamic and antimicrobial photodynamic therapy. We tested these two porphyrins on two cell lines and two bacterial strains to compare effectiveness. In addition, we applied photosensitizers bound in the complex created with hp-β-cyclodextrin. The light-emitting diodes were used at the doses 0, 1, 5, 10 J/cm2 for cells and 0, 150 J/cm2 for bacteria. Tested concentrations for cells and microbes were from 0.5 to 50 μM and from 0.78 to 100 μM, respectively. From this work it can be concluded that TMPyP is a promising compound both in aPDT and in PDT, particularly in contrast to ZnTPPS4, which was efficient only in PDT. Furthermore, the eradication of gram-positive bacteria is possible only with higher concentrations of ZnTPPS4.