To further confirm the occurrence of two steps of sequential one-electron ORRs in cancer cells triggered by the formed GA–Fe nanocomplex, primary HeLa cells were also infected with adenovirus encoding SOD or catalase before FHPG treatment to scavenge the intracellularly generated O2•− or H2O2, respectively, then the cells after FHPG treatment were stained with DCFH-DA and analyzed via flow cytometry (Supplementary Fig. 28). Here, CAT is linked to cancer.