BACKGROUND: Bacterial resistance to antibiotics is a constantly growing challenge. Photodynamic therapy (PDT) offers a new approach to the treatment of bacterial and viral diseases. The aim of this study was to compare the efficacy of photosensitizers used in PDT applied to cell lines and bacterial strains. METHODS: We tested the cytotoxicity and phototoxicity of 3 photosensitizers: TPPS4, ZnTPPS4 and TMPyP applied to the NIH3T3 cell line using two established methods for measuring ROS production and, MTT viability assay. Bacterial viability was determined spectrophotometrically over 24 h following PDT. RESULTS: The most efficient photosensitiser was TMPyP as it reduced the viability of the NIH3T3 cell line by more than 85%. In general, the photosensitisers were more phototoxic to the two Gram-positive bacterial strains, Enterococcus faecalis and Staphylococcus aureus. The viability of E. faecalis was reduced to 78 % by a dose radiation 0.5 J/cm(2) and concentration of TMPyP 1.562 µmol/L. The viability of bacterium S. aureus was reduced to 23 % when exposed to a radiation dose 0.5 J/cm(2) and 100 µmol/L concentration of ZnTPPS4. The highest viability decrease (15 %) for Pseudomonas aeruginosa was caused by 0.5 J/cm(2) radiation dose and 50 µmol/L TMPyP concentration. Escherichia coli proved to be PDT resistant as the bacterial viability was higher than 90%. CONCLUSIONS: The goal of the present study was to test the efficiency of photosensitizers on the NIH 3T3 cell line and bacterial cells. Subsequently we would like to study effectiveness of photosensitizers bound to carriers (for example cyclodextrins) on other cell line and bacterial strain.

Department of Medical Biophysics Faculty of Medicine and Dentistry and Institute of Molecular and Translational Medicine Palacky University Olomouc Czech Republic

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Biological Evaluation of Photodynamic Effect Mediated by Nanoparticles with Embedded Porphyrin Photosensitizer