8 February 2018 Microbial photoinactivation by 470 nm radiation: an investigation into the underlying photobiological mechanism
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Abstract
The photoinactivation properties of 405 (violet) and 470 nm (blue) light have been studied by many research groups within the last few years. Both wavelengths are capable of disinfecting bacteria and fungi, with 405 nm radiation being more efficient. The basic photoinactivation mechanism is understood for 405 nm. Violet light is absorbed by endogenous porphyrins that act as photosensitizers and generate reactive oxygen species, subsequently destroying the microorganisms from within. The underlying photobiological mechanism for 470nm radiation is still unclear though porphyrins and flavins are widely believed to be involved endogenous photosensitizer.

We performed own measurements of disinfection efficacy and additionally did a meta-analysis of published photoinactivation data. The disinfection experiments were performed with LEDs at peak wavelengths between 440 and 490 nm in an interval of about 10 nm. Staphylococcus auricularis was irradiated with doses of 70, 140 and 210 J/cm2 and peak efficacy was observed at 470 nm while the impact of irradiation decreases steeply to lower and higher wavelengths. These observations are supported by the meta-analysis results and rather contradictory to the porphyrin and flavin hypothesis so that our conclusion is that there may be another unknown photosensitizer involved.
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K. Hoenes, K. Wild, J. Schmid, B. Spellerberg, M. Hessling, "Microbial photoinactivation by 470 nm radiation: an investigation into the underlying photobiological mechanism ", Proc. SPIE 10479, Light-Based Diagnosis and Treatment of Infectious Diseases, 104790L (8 February 2018); doi: 10.1117/12.2289110; https://doi.org/10.1117/12.2289110
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