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

In this work, well-defined 3 nm-sized Ca(2+), Fe(3+), Na(+), Mg(2+), Zn(2+), Ni(2+), Co(2+), and Cd(2+) cation-adsorbed Fe(3)O(4)/γ-Fe(2)O(3) 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 Fe(3)O(4)/γ-Fe(2)O(3) nanoparticles. Quantum mechanics analyses revealed that even-parity and odd-parity states of harmonic oscillations are dominant in r(1) and r(2) relaxivities, respectively. Moreover, the harmonic oscillations of Na(+) and Mg(2+) cations around Fe(3)O(4)/γ-Fe(2)O(3) nanoparticles are found to be classical forbidden, which are quite different from their counterparts located in the classical permissive area.