Fig. 4

 A Cytotoxicity of Au@Cu_2−xSe NPs toward 4T1 tumor cells at different concentrations. B 4T1 tumor cell viability after different treatments. Data are presented as mean ± s.d. (n = 6). *P < 0.05, **P < 0.01, ***P < 0.001. C Flow cytometric analysis of 4T1 tumor cells after different treatments. D CLSM images of 4T1 tumor cells after different treatments, where DAPI (blue) and γ-H2AX (red) were used to observe the cell nucleus and DAN damage, respectively. Scale bar = 20 μm. Au@Cu_2−xSe: 50 µg mL⁻¹. H₂O₂: 100 µM. NIR: 808 nm laser, 1.0 W cm⁻² for 5 min