Photocatalytic killing effect of TiO2 nanoparticles on Ls-174-t human colon carcinoma cells

AIM: To investigate the photocatalytic killing effect of photoexcited TiO2 nanoparticles on human colon carcinoma cell line (Ls-174-t) and to study the mechanism underlying the action of photoexcited TiO2 nanoparticles on malignant cells. METHODS: Ls-174-t human colon carcinoma cells were cultured in RPMI 1640 medium supplemented with 199 mL/L calf serum in a humidified incubator with an atmosphere of 50 mL/L CO2 at 37 degrees C. Viable cells in the samples were measured by using the MTT method. A GGZ-300 W high pressure Hg lamp with a maximum ultraviolet-A (UVA, 320-400 nm) irradiation peak at 365 nm was used as light source in the photocatalytic killing test. RESULTS: The photocatalytic killing of Ls-174-t cells was carried out in vitro with TiO2 nanoparticles. The killing effect was weak by using UVA irradiation without TiO2 nanoparticles. In our studies, the photocatalytic killing effect was correlated with the concentration of TiO2 and illumination time. Once TiO2 was added, Ls-174-t cells were killed at a much higher rate. In the presence of 1 000 mu g/mL TiO2, 44% of cells were killed after 10 min of UVA irradiation, and 88% of cells were killed after 30 min of UVA irradiation. CONCLUSION: When the concentration of TiO2 is below 200 mu g/mL, the photocatalytic killing effect on human colon carcinoma cells is almost the same as that of UVA irradiation alone. When the concentration of TiO2 is above 200 mu g/mL, the remarkable killing effect of photoexcited TiO2 nanoparticles can be found.