Applying LEDs as therapeutic light sources for anti-microbial treatment: An experimental study

Microbial infection is one of the most common diseases in the world, which gives rise to morbidity and mortality. At present, the main treatment is using antibiotic drugs. However, the side effects range from fever and nausea to major allergic reactions cannot be ignored. Moreover, the increasing drug resistance also necessitates a new safe alternative therapeutic approach against the microbial infections. As non-antibiotic methods, photodynamic therapies (PDT) and anti-microbial blue light (ABL) therapies have been investigated in this field. However, one challenge of the PDT is the introduction of photosensitizers to the specific pathogens rather than the host cells. In contrast, ABL therapies inactivate the microbes without the involvement of exogenous photosensitizers. The general mechanism of ABL therapies is that ABL can excite the endogenous photosensitizers, and trigger the accumulation of cytotoxic reactive oxygen species (ROS), which in turn leads to cell damage. In this study, we investigated the inhibitive capability of the 405nm LED light source on Candida albicans (C. albicans). C. albicans is the most common pathogen of fungal infections. The intracellular ROS level of C. albicans was detected after the ABL irradiation. The results obtained from this study demonstrated that irradiation of 405nm LED significantly inactivated the C. albicans. The viability of C. albicans was reduced to 1% after 25 minutes of ABL exposure of 50mW/cm². On the other hand, the intracellular ROS was increased by the ABL irradiation. This study demonstrates the effectiveness of applying 405nm LED to threat the infection caused by C. albicans, as the result of the stimulated accumulation of the intracellular cytotoxic ROS by this light.