TiO2 농도 및 여기광에 따른 광촉매 반응이 Streptococcus mutans의 생장에 미치는 영향

Abstract

The aim of this study was to evaluate influences of titanium dioxide (TiO2) concentrations and irradiation times on growth of Streptococcus mutanswhen irradiated by visible light (405 nm wavelength) and by ultraviolet light (254 nm wavelength). To find the optimal antibacterial concentration ofTiO2, 0.01, 0.1, 1.0, and 10.0 mg/ml TiO2 suspension was prepared with sterilized distilled water. S. mutans cultured media was added to TiO2solution to set the final cell count to 104 CFU/ml. The photocatalytic reaction was induced by irradiating 254 nm and 405 nm lights for 10 minutes. To compare the bactericidal activities according to irradiation times, all photocatalytic reaction was carried out with 0.1 mg/ml TiO2 for 0, 10, 20,30, and 40 minutes with both lights. After the photocatalytic reaction, 100 μm of the reaction mixture was immediately plated on brain heart infusionagar. These plates were placed at 5% CO2, 37oC, for 24 hours and the bacterial colonies were counted. All experiments were performed inquintuplicate. One-way ANOVA was used to determine whether there were any significant differences between the TiO2 concentrations or theirradiation times. The most effective concentration of TiO2 for its photocatalytic bactericidal effect on S. mutans was 0.1 mg/ml when irradiated with254 nm and 405 nm lights. The longer the irradiation time, the bigger the bactericidal effect for both wavelengths. Over 99% of bacteria in theinoculum were killed after irradiation with 254 nm for 20 minutes and with 405 nm for 40 minutes. In conclusion, a photocatalytic reaction of TiO2induced by visible light of 405 nm constitutes the bactericidal effect on S. mutans.