Antibacterial Properties of Visible-Light-Responsive Carbon-Containing Titanium Dioxide Photocatalytic Nanoparticles against Anthrax

Sun, Der-Shan; Kau, Jyh-Hwa; Huang, Hsin-Hsien; Tseng, Yao-Hsuan; Wu, Wen-Shiang; Chang, Hsin-Hou

The bactericidal activity of conventional titanium dioxide (TiO(2)) photocatalyst is effective only on irradiation by ultraviolet light, which restricts the applications of TiO(2) for use in living environments. Recently, carbon-containing TiO(2) nanoparticles [TiO(2)(C) NP] were found to be a visible-light-responsive photocatalyst (VLRP), which displayed significantly enhanced antibacterial properties under visible light illumination. However, whether TiO(2)(C) NPs exert antibacterial properties against Bacillus anthracis remains elusive. Here, we evaluated these VLRP NPs in the reduction of anthrax-induced pathogenesis. Bacteria-killing experiments indicated that a significantly higher proportion (40%–60%) of all tested Bacillus species, including B. subtilis, B. cereus, B. thuringiensis, and B. anthracis, were considerably eliminated by TiO(2)(C) NPs. Toxin inactivation analysis further suggested that the TiO(2)(C) NPs efficiently detoxify approximately 90% of tested anthrax lethal toxin, a major virulence factor of anthrax. Notably, macrophage clearance experiments further suggested that, even under suboptimal conditions without considerable bacterial killing, the TiO(2)(C) NP-mediated photocatalysis still exhibited antibacterial properties through the reduction of bacterial resistance against macrophage killing. Our results collectively suggested that TiO(2)(C) NP is a conceptually feasible anti-anthrax material, and the relevant technologies described herein may be useful in the development of new strategies against anthrax.