Role of visible light-activated photocatalyst on the reduction of anthrax spore-induced mortality in mice.
BACKGROUND
Photocatalysis of titanium dioxide (TiO(2)) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO(2) substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis.


RESULTS
Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components.


CONCLUSIONS
Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host.
Kau
Jyh-Hwa
JH
Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan.
Sun
Der-Shan
DS
Huang
Hsin-Hsien
HH
Wong
Ming-Show
MS
Lin
Hung-Chi
HC
Chang
Hsin-Hou
HH
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000942:Antigens, Bacterial / Q000378:metabolism; D001408:Bacillus anthracis / Q000472:pathogenicity / Q000528:radiation effects*; D001412:Bacillus subtilis / Q000378:metabolism; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008027:Light; D051379:Mice; D008810:Mice, Inbred C57BL; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013171:Spores, Bacterial / Q000472:pathogenicity / Q000528:radiation effects; D014025:Titanium / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D017319:Photosensitizing Agents; C030325:anthrax toxin; C009495:titanium dioxide; D014025:Titanium