著者

Tomoyuki Nakada Kiyoshi Konishi

出版者

The Pharmaceutical Society of Japan

雑誌

BPB Reports (ISSN:2434432X)

巻号頁・発行日

vol.6, no.3, pp.81-86, 2023 (Released:2023-05-12)

参考文献数

36

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Irradiation with 405-nm visible violet LED light without additional photosensitizers decreased the viability of the aggressive periodontopathic bacterium Aggregatibacter actinomycetemcomitans. The number of CFU/mL decreased linearly on a logarithm chart versus irradiation time, with a 1-log reduction time of 1.32 min. The antimicrobial photodynamic effect of 405-nm LED light involved inhibition of the activity of membrane-bound cytochrome bd, a terminal quinone: oxygen oxidoreductase, and quinol peroxidase, a terminal quinone:H2O2 oxidoreductase. The 405-nm LED irradiation reduced minus oxidized difference spectrum showed that the 640-nm peak (α-peak of heme d) completely disappeared, and the height of the 556-nm (α-peak of hemes b and c) and Soret band (425 nm; γ-peak of hemes b, c, and d) was reduced to approximately half of the peak heights of non-irradiated controls. Survival of bacteria-injected silkworm larvae was also examined. Fifth-instar silkworm larvae were almost completely killed by approximately 40 h after bacterial injection, but almost all silkworm larvae irradiated with 405-nm LED light (20 mW/cm2 for 5 min, energy density: 6 J/cm2) survived, similar to controls not injected with bacteria, indicating that 405-nm LED light killed the injected bacteria. The bactericidal effect of 405-nm blue-light on A. actinomycetemcomitans is primarily due to disruption of cytochrome bd oxidase and quinol peroxidase of the respiratory chain.