Multifunctional Bismuth Ferrite Nanoparticles as Magnetic Localized Dose Enhancement in Radiotherapy and Imaging.

Recently bismuth-based nanoparticles have drawn extensive attention as radiosensitizer in radiotherapy due to high atomic number, low toxicity, and low cost. This study aims to introduce the applicability of bismuth ferrite nanoparticles (BFO, BiFeO3) as a new multifunctional theranostic agent for radiotherapy, magnetic resonance imaging (MRI), and computed tomography (CT) as well as magnetic hyperthermia mediator. After evaluation of BFO nanoparticles biocompatibility which were synthesized by conventional sol-gel method, we investigated dose enhancement property of BFO nanoparticles with gel dosimetry, clonogenic, and cck8 assay. According to clonogenic assay, sensitizer enhancement ratios (SERs) were obtained as 1.35 and 1.76 for nanoparticle concentrations of 0.05 mg/ml and 0.1 mg/ml, respectively. For high concentration (0.5 mg/ml), dose enhancement effect of BFO nanoparticles was demonstrated by gel dosimetry. To prove the contrast enhancement of BFO nanoparticles in MR and CT imaging, the relaxation time rate (R2) and Hounsfield unit (HU) were measured, respectively. It was found that the R2 and Hu have linear relationship with the nanoparticle concentrations. Moreover, whereas BFO nanoparticles have magnetic properties, we measured inductive heating property of the nanoparticles in external alternative magnetic field to evaluate their applicability as magnetic hyperthermia mediator. A rapid temperature increment was detected under alternative magnetic field (12.2 kAm-1 and 17.2 kAm-1, frequency 480 kHz) owing to the high concentration of BFO nanoparticles. Collectively, our experimental investigation results proved that the multifunctional BFO nanoparticles could be employed as a multimodal imaging and radio-thermotherapeutic agent to enhance theranostic efficacy.