Fig. 1. Amplified oxidation stress by modulating redox homeostasis with PDA–MB for highly effective synergistic phototherapy to inhibit primary tumors and metastases. The nanocarriers effectively load and deliver the photosensitizer (MB) into cancer cells. Then, stimulated by overexpressed GSH, MB is released from PDA–MB to generate ROS under irradiation. In the meantime, besides acting as a photothermal agent, PDA depletes GSH and thus disturbs the antioxidant capacity of cancer cells for amplifying intracellular ROS levels. Consequently, the nanoplatform allows remarkably enhanced PDT and PTT, as well as multimodal imaging (fluorescence, photothermal, and photoacoustic images), leading to strong inhibition of primary tumor growth and cancer metastasis both in vitro and in vivo.