Abstract-The antimicrobial photodynamic activity of protoporphyrine IX (PPIX) in conjunction with red lightemitting diode (LED) and xenon lamp was carried out against Staphylococcus aureus (S.aureus). At 30min illumination using the red LED and 30µM of PPIX 99.8% reduction of S.aureus survival was achieved. Based on optofluorometric study, it is further observed that the measurement of steady-state native fluorescence of amino acid, tryptophan provided a method to monitor the Antimicrobial photodynamic therapy (APDT) efficiency by optical means.Index Terms-Antimicrobial photodynamic therapy, red LED, protoporphyrine IX.
Antimicrobial photodynamic therapy (APDT) has been considered to treat skin diseases infected by drug resistant microorganisms. In this work, attempts were made to study the effectiveness of APDT with protoporphyrin IX (PPIX) in the presence of gold nanoparticles (GNPs) or hydrogen peroxide (H 2 O 2 ) against the human bacterial pathogen, Staphylococcus aureus. To photoactivate the PPIX, xenon light source was used at 626 nm. The bactericidal effect was analyzed by standard plate counting method. Attempts were also made to study whether fluorescence spectroscopy can be used to characterize the damage at protein level. Results of the study revealed that PPIX with H 2 O 2 has showed higher bactericidal effect than that of PPIX alone and PPIX with GNPs. From fluorescence spectroscopic characterization it was found that protein damage is one of the reasons of bactericidal effect as there is a considerable change in the intensity of emission and fluorescence lifetime of tryptophan present in the microorganism between pre and post APDT.
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