Curcumin combined with red united blue light irradiation restrained cell viability.

HaCaT cells were pre-treated with curcumin (0–5 μM) for 2 h, and then separately irradiated with blue light, red light and two combinations of blue and red light, or protected from light. Cells without any treatment were used as a control. Cell viability was examined by CCK-8 assay 20 h after the last treatment. The values of the control were set to 100%. Each bar represents the mean of three independent experiments. The suppression rate is depended on the concentration of curcumin, and the differences between cells treated with light irradiation or not are particularly evident at p<0.05(*) or p<0.01(**) level.