Fig. 2. In vitro ROS generation and phototoxicity of COEs.

(A) Intracellular ROS evaluation using DCFH-DA probe for A549 cells treated by 5 μM COEs and white light irradiation (5 min, 20 mW cm⁻²) with PBS as control. (B) Micrographs of Ben- or S6-incubated A549 cells with or without light treatments, followed by double staining using calcein-AM (for viable cells, presented in green) and propidium iodide (PI; for dead cells, presented in red). Scale bars, 50 μm. (C) Live and dead cell subpopulation analyses using flow cytometry. (D and E) Viability of A549 cells that preincubated with different concentrations of Ben or S6 and treated by white light irradiation at 20 mW cm⁻² for 10 min. (F) Photothermal effects of 20 μM Ben or S6 in PBS under 10 min of white light exposure at 20 mW cm⁻². Neat PBS was used as control. (G) DFT-evaluated relative potential energy of Ben and S6 backbones along the dihedral between central core and stilbene wing segments, from trans-planar to cis-planar.