To examine the special features of the antibacterial effect for a thin transparent titanium dioxide (TiO{sub}2) film, the photocatalytic degradation of endotoxin, which is a pyrogenic constituent of Escherichia coli (E. coli), as well as itsbactericidal activity, was investigated. The TiO{sub}2 films were prepared from titanium isopropoxide solution, annealing at 500 0C. The bactericidal activity for E. coil cells was estimated by survival ratio calculated from the number of viable cellswhich form colonies on the nutrient agar plates. The endotoxin concentration was determined by the Limulus tests. When F. coil cells were killed by the TiO{sub}2 photocatalyst under UV irradiation, the endotoxin from the cells was also degradedefficiently. This result shows that the TiO{sub}2 photocatalyst has both bactericidal activity and decomposing activity for the endotoxin (i.e., detoxifying activity). The bactericidal effect of the TiO{sub}2 thin film results from both inactivating theviability of the bacteria and the destruction of the E. coil cells. This feature renders TiO{sub}2 photocatalysts to be applicable to environmental protections, especially in medical facilities where the endotoxin is needed to control.
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