FIG. 4.

Radiation survival curves of HeLa cells after being pre-exposed to low-level laser irradiation (LLLI). The cells were illuminated by LLLI at 1 and 5 J/cm² with 685 and 830 nm wavelengths. One hour later, cells were radiated with different doses of ionizing radiation. LLLI at 5 J/cm² with 685 nm significantly sensitized HeLa cell to ionizing radiation (A). The radiation survival curve of HeLa cells after being pre-exposed to 830 nm LLLI was not significantly different (B). Survival data were fitted to the linear quadratic model. Error bar indicates standard error of the mean of at least three independent experiments in triplicate. *p<0.05 compared with the corresponding control.