Glutathione-Responsive Nanoplatforms Based on Coordination between Fe³⁺ and Apigenin for Synergistic Chemo/Chemodynamic Therapy

The oxygen consumption during chemodynamic therapy (CDT) can lead to severe cellular hypoxia, resulting in an increase in the hypoxia inducible factor-1α (HIF-1α) level, which hinders the effectiveness of CDT and induces tumor metastasis. Here, we propose a strategy of synergistic therapy between CDT and the HIF-1α inhibitor to avoid the limitations of CDT and reduce the risk of metastasis. Herein, based on the coordination between Fe3+ and apigenin (API, HIF-1α inhibitor), we constructed a hyaluronic acid (HA)-modified API-Fe nanoparticles (AF@HA NPs) for synergetic chemotherapy and glutathione (GSH)-activated self-enhancing CDT. AF@HA NPs have high drug loading capacity, stability, and biocompatibility. Furthermore, the overexpressed GSH in cancer cells can reduce Fe3+ to Fe2+, weakened the coordination between API and Fe, and promoted the release of API for chemotherapy. Fe2+ could react with endogenous H2O2 to generate hydroxyl groups for CDT. In addition, the released API could inhibit the expression of HIF-1α and increase the sensitivity of cells to reactive oxygen species (ROS), thereby achieving a synergistic effect between self-enhancing CDT and chemotherapy. The results of in vitro and in vivo experiments indicated that AF@HA NPs could effectively inhibit tumor growth and suppress the lung metastasis of tumor cells.