Histological Data-Based Examination of the Safety of Anti-microbial Light Therapies

Anti-microbial light therapies have been proven to be effective in treating various diseases caused by microbial infection. The existing literature has been mainly devoted to studying the effect of various light dosages on inhibiting microbes. Studying the safety of light therapies to normal host cells, especially via in vivo experiments, has not yet attracted much attention. In this work, we extend our previous study on evaluating the treatment efficacy based on histological image data to the examination of the treatment safety by blue LED light. Specifically, the anti-microbial light experiments using 415-nm-wavelength LED light were performed on BALB/c mice, whose skin was infected by Candida albicans (C. albicans), which is a common pathogenic fungal species. The tissue sections of the experimental animals were processed by TUNEL staining for examining the treatment safety. The apoptosis rates of the epithelial cells before and after the light treatment were extracted from the histological data, and tested. The results showed that the host cells were not significantly inhibited by the light, whose dosage was enough to significantly inhibit the fungi. Moreover, to discover the cytotoxic effect of the light on the fungal cells, the induced intracellular reactive oxygen species (ROS) was also measured. The increase in the ROS levels due to the light stimulation was found to be significant, as tested against those in the control group that was not treated by the light. Overall, the results verified the safety of the anti-microbial therapy by the 415-nm-wavelength LED light.