<p>(a) T98G, SNU80, KB and HEK293 cells were treated with the oxidation-sensitive fluorescent probe 2,7-dichlorodihydrofluorescein diacetate (H<sub>2</sub>DCFDA) for detection of total ROS, (b) detection of H<sub>2</sub>O<sub>2</sub> level (in µM) in cells observed at 24 h after exposure. In (a) and (b), all fluorescence levels were expressed as fluorescence intensity (FL intensity). Results from four independent experiments are shown as mean ± SD, and Student’s <i>t</i>-test was performed to controls (*<i>p</i><0.05 and **<i>p</i><0.01).</p
