Electron Pump and Photon Trap Effect-Derived Selective Antitumor of Fe-Ppy@CaO₂-Modified Polyetheretherketone for Bone Tumor Therapy

Bone tumors with high mortality and disability have become a major clinical challenge. Herewith, it is necessary to design materials for bone tumor therapy and bone repair. In this work, Fe-doped polypyrrole (Fe-Ppy) and CaO₂ are constructed on sulfonated polyetheretherketone (SP) to form a multistage-responsive coating. The coating achieves long-lasting antitumor through chemodynamic therapy (CDT), photothermal therapy (PTT), and combined immunotherapy. Fe-Ppy acts as an electron pump to replenish Fe²⁺ through oxidizing -NH- to -N⁺-, which lasts the Fenton reaction and persistently produces reactive oxygen species (ROS) in the tumor microenvironment (TME). CaO₂ selectively provides exogenous H₂O₂ in response to TME to boost the electron cycle. Stronger near-infrared light absorption due to Fe doping and more photon traps caused by porous structure-induced scattering and refraction diminishment improve the photothermal conversion of modified SP. Furthermore, long-lasting ROS and effective photothermal conversion enhance M1 activation to secrete TNF-α and IFN to kill tumor cells. After tumor therapy, Fe-Ppy@CaO₂-modified SP could adaptively switch the macrophage to M2 and promote osteogenesis with the abolishment of TME and NIR stimulation. In summary, Fe-Ppy@CaO₂-modified SP with long-lasting ROS, enhanced photothermal conversion, and immunomodulation is a potential candidate for bone tumor therapy and tissue repair.