IC/IR820 NPs-mediated ROS induce breast cancer cell death. (A–C) Immunofluorescence images to show subcellular localization of IR820 and IC/IR820 NPs. Scale bar: 20 μm. (D) Fluorescence microscopy images and (E) flow cytometry analysis for intracellular ROS generation of MDA-MB-231 cells using DCFH-DA as a probe. Scale bar: 20 μm. (λ = 808 nm, P = 1.0 W/cm2; irradiation time = 2 min). (F–H) Flow cytometry statistical analysis for intracellular ROS generation of MDA-MB-231, MCF-7 and 4T1 cells using DCFH-DA as a probe. Scale bar: 20 μm. (λ = 808 nm, P = 1.0 W/cm2; irradiation time = 2 min). (I–K) Viability of specific groups with or without NAC treatment in MDA-MB-231, MCF-7 and 4T1 cells. (λ = 808 nm, P = 1.0 W/cm2; irradiation time = 20 s).