NOBF₄-Functionalized Au-Fe₃O₄ Nanoheterodimers for Radiation Therapy: Synergy Effect Due to Simultaneous Reactive...

Snowman-shaped Au-Fe₃O₄ nanoheterodimers were synthesized by thermal decomposition of iron oleate on presynthesized Au nanoparticles. Subsequently performed ligand exchange with nitrosyl tetrafluoroborate provided water solubility and enabled X-ray-induced NO release. These Au-Fe₃O₄ nanoheterodimers combine high- Z material with catalytically active Fe₃O₄ surfaces and, moreover, plasmonic properties with superparamagnetic performance. We could establish synergetic interactions between X-radiation and both the Au and Fe₃O₄ surfaces, which resulted in the simultaneous production of the nitric oxide radical at the Fe₃O₄ surface and the superoxide radical at the Au surface. The surface-confined reaction between these radicals generated peroxynitrite. This highly reactive species may cause nitration of mitochondrial proteins and lipid peroxidation and induce DNA strand breaks. Therefore, high concentrations of peroxynitrite are expected to give rise to severe cellular energetic derangements and thereupon entail rapid cell death. As providing a common platform for X-ray-induced formation of the highly reactive radical nitric oxide, superoxide, and peroxynitrite, nitrosyl tetrafluoroborate functionalized Au-Fe₃O₄ nanosnowmen were shown to exhibit excellent performance as X-ray-enhancing agents in radiation therapy.