Fig. 3. PDA facilitates ROS generation by scavenging GSH. (A) GSH depletion capacity of PDA calculated by recording the absorption intensity of DTNB at 412 nm. The result is expressed as the plot of the added amount of PDA versus the reacted levels of GSH. (B) Time-dependent changes of GSH levels in the presence of PDA or PDA–MB. (C) Ability of different systems to generate ROS under irradiation. Fluorescence spectra of DCF were recorded and compared for illustrating the capacity of PDA to boost ROS production. (D) Assay of the released MB level from PDA–MB with GSH stimulus. Fluorescence intensities of MB derived from different systems were recorded for normalization. The concentrations of PDA–MB, MB and GSH were 100 μg mL⁻¹, 2 μg mL⁻¹ and 1 mM, respectively. Laser: 660 nm, 250 mW cm⁻². Values are presented as mean ± SD (n = 3).