Chlorin e6 (Ce6) is a promising photosensitizer for tumor photodynamic therapy (PDT). However, the efficacy of Ce6 PDT is limited by Ce6’s poor water solubility, rapid blood clearance, and inadequate accumulation in the tumor tissue. This problem is tackled in this work, wherein functionalized superparamagnetic iron oxide nanoparticles (IO-NPs) were used as carriers to deliver Ce6 to melanoma. The IO-NPs were coated with polyglycerol (PG) to afford good aqueous solubility. The chemotherapeutic agent doxorubicin (DOX) was attached to the PG coating via the hydrazone bond to afford affinity to the cell membrane and thereby promote the cell uptake. The hydrophobic nature of DOX also induced the aggregation of IO-NPs to form nanoclusters. Ce6 was then loaded onto the IO nanoclusters through physical adsorption and coordination with surface iron atoms, yielding the final composites IO–PG–DOX–Ce6. In vitro experiments showed that IO–PG–DOX–Ce6 markedly increased Ce6 uptake in mouse melanoma cells, leading to much-enhanced photocytotoxicity characterized by intensified reactive oxygen species production, loss of viability, DNA damage, and stimulation of tumor cell immunogenicity. In vivo experiments corroborated the in vitro findings and demonstrated prolonged blood clearance of IO–PG–DOX–Ce6. Importantly, IO–PG–DOX–Ce6 markedly increased the Ce6 distribution and retention in mouse subcutaneous melanoma grafts and significantly improved the efficacy of Ce6-mediated PDT. No apparent vital organ damage was observed at the same time. In conclusion, the IO–PG–DOX NPs provide a simple and safe delivery platform for efficient tumor enrichment of Ce6, thereby enhancing antimelanoma PDT.

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Background Chemodynamic therapy (CDT) relying on intracellular iron ions and H2O2 is a promising therapeutic strategy due to its tumor selectivity, which is limited by the not enough metal ions or H2O2 supply of tumor microenvironment. Herein, we presented an efficient CDT strategy based on Chinese herbal monomer-dihydroartemisinin (DHA) as a substitute for the H2O2 and recruiter of iron ions to amplify greatly the reactive oxygen species (ROS) generation for synergetic CDT-ferroptosis therapy. Results The DHA@MIL-101 nanoreactor was prepared and characterized firstly. This nanoreactor degraded under the acid tumor microenvironment, thereby releasing DHA and iron ions. Subsequent experiments demonstrated DHA@MIL-101 significantly increased intracellular iron ions through collapsed nanoreactor and recruitment effect of DHA, further generating ROS thereupon. Meanwhile, ROS production introduced ferroptosis by depleting glutathione (GSH), inactivating glutathione peroxidase 4 (GPX4), leading to lipid peroxide (LPO) accumulation. Furthermore, DHA also acted as an efficient ferroptosis molecular amplifier by direct inhibiting GPX4. The resulting ROS and LPO caused DNA and mitochondria damage to induce apoptosis of malignant cells. Finally, in vivo outcomes evidenced that DHA@MIL-101 nanoreactor exhibited prominent anti-cancer efficacy with minimal systemic toxicity. Conclusion In summary, DHA@MIL-101 nanoreactor boosts CDT and ferroptosis for synergistic cancer therapy by molecular amplifier DHA. This work provides a novel and effective approach for synergistic CDT-ferroptosis with Chinese herbal monomer-DHA and Nanomedicine. Graphical Abstract