Ultra-small bimetallic iron–palladium (FePd) nanoparticle loaded macrophages for targeted tumor photothermal therapy in NIR-II biowindows and magnetic resonance imaging

Nanoparticles working in the NIR-II biowindows possess larger maximum permissible exposure (MPE) and desirable penetration depth to the laser. However, most NIR-II responsive nanomaterials lack tumor targeting and Magnetic Resonance Imaging (MRI) ability. This greatly limits their applications. This study reported ultra-small bimetallic iron–palladium (FePd) nanoparticle loaded macrophages for targeted tumor photothermal therapy in NIR-II biowindows and magnetic resonance imaging. The crystal phase, morphology, absorption spectrum and photothermal performance of the synthesized samples were systematically characterized. The effects of photothermal therapy and nuclear magnetic imaging (MRI) were studied both in vitro and in vivo. Since FePd nanoparticles have both iron and palladium elements, it had a good MRI imaging capability and high photothermal conversion efficiency (36.7%). After binding to macrophages, FePd nanoparticles@macrophages (FePd@M) showed a good tumor targeting ability and were used for targeting NIR-II photothermal therapy and MRI imaging of tumors. The results of photothermal treatment showed that the tumor volume decreased by 90% compared to the control group, and no significant organ toxicity was observed. The results of MRI imaging showed that the FePd@M has the best imaging effect. The nanoparticles with the excellent NIR-II PTT ability and MRI effect have overcome the problem of tumor targeting and avoid the rapid removal of ultra-small nanoparticles. The FePd@M delivery system provides new ideas for material construction in the NIR-II region and has great clinical application potential.