Figure 4From: Comparison of the killing effects between nitrogen-doped and pure TiO2 on HeLa cells with visible light irradiationChanges of the intracellular NO levels as a function of the time after the PDT. The averaged fluorescence intensity of control cells (white triangle) was set as 100%. TiO2 (white square)- or N-TiO2 (black circle)-treated cells were incubated with 100 μg/ml under light-free conditions for 2 h before the irradiation.Back to article page