A Comparative Analysis of aPDI Effect of Phenothiazinium Dyes in Presence of Inorganic Salt as Potentiator

Photodynamic therapy is a non-invasive therapeutic modality that has gained much attention in the last few decades. It involves administration of a photoactivatable substance, called photosensitizer (PS) into the body, and this substance, upon receiving light can generate reactive oxygen species (ROS), which could subsequently destroy nearby malignancies. The technique has been widely used for cancer treatment, but is also of significance to fight against infectious diseases. For the purpose of this study, Enterococcus faecalis, a bacterial strain common in oral cavities, gastrointestinal system, and wound infections, was selected and its antimicrobial photodynamic inactivation (aPDI) effect with the phenothiazinium dye Toluidine Blue Ortho (TBO) using a 635 nm diode laser was observed. To investigate the possibility of aPDI enhancement, potassium iodide (KI), an inorganic salt which has been proven to have antimicrobial use in dermatology, was used as a potentiating mediator, in order to give a comparative account of the aPDI effect. Laser power was set at 300 mW with irradiation times of 30, 60, and 180 s. Photosensitizer and inorganic potentiator concentration ranges were selected to be 100 mu M(TBO) and 100 mM(KI) respectively. Noticeable potentiation of aPDI effect was observed, especially for 60 and 180 s irradiation groups.