Photodynamic inactivation (PDI) is a process that uses photosensitizing substances to produce reactive oxygen species. This is achieved by exposing photosensitizers to specific wavelengths of light and causing oxidative damage in cells. This sterilization technique is commonly utilized and has been extensively investigated owing to its environmentally friendly and inert characteristics. In this study, erythrosine was selected as the photosensitizer and a green light-emitting diode was used as the light source. Due to their excellent biocompatibility, gold nanoparticles were added; these acted as a carrier for erythrosine, linking it to Escherichia coli (E. coli) cells. Colony-forming unit plate counting and LIVE/DEAD bacterial viability tests were performed. A synergic PDI effect of the photosensitizer, light, and gold nanoparticles was demonstrated. After irradiation for 9 min, a bacterial death rate higher than 97% was achieved. Finally, to study the mechanism of E. coli death, we conducted reactive oxygen species tests by adding different scavengers, and concluded that the bacterial death was due to the production of singlet oxygen (Type II reaction).
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