The effect of RF on reactive oxygen species (ROS) production. (A) The accumulation of ROS green fluorescence was observed. ROS oxidizes DCFH-DA to DCF, emitting green fluorescence. Bar, 20 μm. (B) The relative percentage of ROS-positive cells was shown by flow cytometry. FITC, fluorescein isothiocyanate. (C) Histogram analysis showed the percentage of ROS-positive cells. Data were analyzed by ANOVA (ns, P > 0.05; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001).