BACTERICIDAL AND DETOXIFICATION EFFECTS OF TIO2 THIN-FILM PHOTOCATALYSTS

To examine the special features of the antibacterial effect for a thin transparent titanium dioxide (TiO2) film, the photocatalytic degradat ion of endotoxin, which is a pyrogenic constituent of Escherichia coli (E. coli), as well as its bactericidal activity, was investigated. Th e TiO2 films were prepared from titanium isopropoxide solution, anneal ing at 500 degrees C. The bactericidal activity for E. coli cells was estimated by survival ratio calculated from the number of viable cells which form colonies on the nutrient agar plates. The endotoxin concen tration was determined by the Limulus tests. When E. coli cells were k illed by the TiO2 photocatalyst under UV irradiation, the endotoxin fr om the cells was also degraded efficiently. This result shows that the TiO2 photocatalyst has both bactericidal activity and decomposing act ivity for the endotoxin (i.e., detoxifying activity). The bactericidal effect of the TiO2 thin film results from both inactivating the viabi lity of the bacteria and the destruction of the E. coli cells. This fe ature renders TiO2 photocatalysts to be applicable to environmental pr otections, especially in medical facilities where the endotoxin is nee ded to control.