Antibacterial photodynamic therapy with indocyanine green and near-infrared light

Increase in antibiotic-resistance is a worldwide health problem, which may result in septicemia and subsequent death in recent years. Some of these deaths are caused by nosocomial, burn or chronic wound infections. Photodynamic therapy can be an alternative technique in treatment of infections. This research aimed to investigate the bactericidal effect of photodynamic therapy with indocyanine green and near-infrared light in vitro and in vivo. First, the effect of indocyanine green and 809-nm laser light was examined on wild type and resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa in vitro. Indocyanine green concentration and laser dose were initially optimized for wild type strains. After determining most effective concentrations with specified light dose, they were applied on resistant strains. This method was totally efficient to kill these strains and optimum doses varied with different strains. Later, this method was examined on rat excisional and abrasion wound models. Wounds were infected by resistant strains of S. aureus and P. aeruginosa. Optimum parameters could not be found for excisional wounds because of bleeding, but infected abrasion wounds could be successfully treated. Around 90\% reduction in bacterial burden was observed. Applied energy dose did not cause any thermal damage on healthy tissue. This study showed that indocyanine green together with near-infrared light might be a promising antibacterial method to eliminate infections in clinics and accelerate wound healing process.