Two-step upconversion-driven PDT/CDT cooperative phototherapeutic platform based on surface magnetic field modulation

Photodynamic therapy utilizes photosensitizer to generate reactive oxygen species (ROS) under irradiation of light for anticancer. However, due to the strong absorption of visible light by tissues and organs, photodynamic therapy meets challenges in deep tissues. Herein, we propose an upconversion-driven photodynamic therapy combined with chemodynamic therapy based on UCNP@SiO₂@Fe₃O₄@MC540. Upon the excitation of 980 nm laser, the visible emission of upconversion nanoparticles activates MC540 to produce ROS, which is enhanced by Fe₃O₄ through magnetic field modulation. Subsequently, Fe₃O₄ degrades under acidic conditions to produce ·OH via Fenton-reaction for chemodynamic therapy. The in vitro and in vivo experiments indicate that the two-step cooperative strategy exhibits significant anticancer efficacy. Besides, Finite Difference Time Domain (FDTD) simulation reveals that the enhancement stems from surface electric field and light absorption. It offers a deeper understanding of phototherapeutic process.