Applications of visible blue light as a multipurpose disinfecting tool for medicine and public health: an overview
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Visible blue light wavelengths in the 400-470-nm range have been observed to have antimicrobial properties. The purpose of this review article is to delineate the mechanism of action, optimizing conditions, and public health and clinical applications of antimicrobial blue light (aBL) as characterized by the current literature. A widely accepted hypothesis for the mechanism of bacterial inactivation by aBL is that the light causes photoexcitation of endogenous photosensitizers, porphyrins and flavins, which leads to the release of reactive oxygen species that subsequently lead to cell toxicity. Factors that have been observed to be associated with enhanced antimicrobial action include increased duration of exposure, pre-treatment with quinine hydrochloride, and exposure of target bacteria to sub-lethal stress conditions. Studies examining the effect of repetitive exposure to sub-lethal levels of aBL on bacteria show no significant evidence of development of resistance. Additionally, aBL has exhibited the ability to inactivate multidrug-resistant (MDR) bacteria. While studies have also observed aBL to have efficacy in inactivating fungal and viral pathogens, there is a need for further research to elucidate the mechanisms of photoinactivation of fungi and viruses by aBL. Multiple studies have shown that aBL is effective in causing significant CFU reduction in biofilms, an observation that supports the application of aBL for decontamination of surfaces and treatment of localized infections. aBL has demonstrated efficacy in eliminating foodborne pathogens found on food surfaces and exposed surfaces in the food processing environment. Studies applying aBL to decontamination of surfaces in the clinical environment have concluded that it is a viable decontamination practice that shows promise for helping to minimize the spread of healthcare-associated infections (HAIs). Existing literature provides evidence in favor of the application of aBL in clinical contexts such as the treatment of gonococcal infections, eye infections, and otitis media, and in the decontamination of stored platelets and plasma. Studies investigating these clinical applications have demonstrated the efficacy of aBL for inactivating the clinically relevant pathogens, as well as the preservation of normal human cells upon exposure to the doses of light that are lethal to the pathogens.