Bifunctional Au–Fe₃O₄ Nanoheterodimers Acting as X-ray Protector in Healthy Cells and as X-ray Enhancer in Tumor Cells

Bifunctional Au–Fe3O4 nanoheterodimers were synthesized by thermally decomposing Fe(III)oleate on gold nanoparticles followed by functionalizing with tiron, 2,3-dihydroxybenzoic acid, or caffeic acid. These catechol derivatives are antioxidative and thus are predicted to function as superoxide scavengers. In particular, caffeic acid lost its antioxidant capacity, although it was covalently linked through its carboxyl moiety to the Fe3O4 surface. Tiron was shown to bind via its catechol group to the Au–Fe3O4 nanoheterodimers, and 2,3-dihydroxybenzoic was just physisorbed between the oleic acid surface structures. Caffeic-acid stabilized Au–Fe3O4 nanoheterodimers turned out to act as X-ray protector in healthy cells but as X-ray enhancing agents in cancer cells. Furthermore, these functionalized Au–Fe3O4 nanoheterodimers were found to inhibit the migratory capacity of the cancer cells.