Abstract

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 (H₂O₂) 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. Attemptswere 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 H₂O₂ 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.

Key words: Photodynamic therapy, hydrogen peroxide, gold nanoparticles,Staphylococcus aureus, antimicrobial photodynamic therapy.