Impact of metallic trace elements on relaxivities of iron-oxide contrast agents.

In this work, well-defined 3 nm-sized Ca, Fe, Na, Mg, Zn, Ni, Co, and Cd cation-adsorbed FeO/γ-FeO nanoparticles were used as prototype systems to investigate the influence of metallic trace elements in body fluids on the relaxivities of iron-oxide contrast agents. It was found that surface-adsorbed cations formed a deterioration layer to induce pronounced relaxivity loss. Theoretical study showed that such relaxivity loss can be well described by a modified GCAS function, taking into account the harmonic cation oscillations around FeO/γ-FeO nanoparticles. Quantum mechanics analyses revealed that even-parity and odd-parity states of harmonic oscillations are dominant in and relaxivities, respectively. Moreover, the harmonic oscillations of Na and Mg cations around FeO/γ-FeO nanoparticles are found to be classical forbidden, which are quite different from their counterparts located in the classical permissive area.