Iron Borate Nanobeams for Magnetic Resonance Imaging-Guided Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) has received significant attention due to its effectiveness in treating tumors. Preclinical and clinical studies have sought materials with a high boron content. Meanwhile, imaging-guided BNCT can not only enable the determination of the optimal neutron irradiation time and the required dose but also hold substantial significance for evaluating the therapeutic effects. Herein, iron borate (Fe₂B₂O₅) nanobeams were synthesized via the thermal decomposition method. First, iron borate nanobeams are rich in boron, providing sufficient boron for BNCT. Second, the magnetic properties of the nanobeams enable enhancement of magnetic resonance imaging (MRI) contrast, facilitating the monitoring of the agent's distribution. The size and morphology of the nanobeams can be tuned by varying the synthesis temperature, time, and precursor concentration. To enhance the colloidal stability and biocompatibility, the iron borate nanobeams were coated with a layer of silica (IBNBs@SiO₂). The <i>in vitro</i> and <i>in vivo</i> experiments demonstrate that IBNBs@SiO₂ functions as a T1 contrast agent. Furthermore, cells and mice treated with IBNBs@SiO₂ followed by thermal neutron irradiation demonstrated the effective suppression of melanoma growth. Therefore, IBNBs have potential for MRI-guided BNCT.