Porous Mn2+ - Fe3O4 Nanoparticles with High T1 and T2 Relaxivity

Veronica Clavijo Jordan¹, Michael R. Caplan¹, Kevin M. Bennett¹

We report a protein based nanoparticle with a Fe₃O₄ crystal core and Mn²⁺ bound to surface channels. The metal core size ranged from 3 to 6nm in diameter, and ICP results indicate 7 Mn²⁺ per protein. HRTEM shows that the core metal is magnetite with a lattice spacing of 0.25nm. Following the proposed synthesis, we suspect that the high per-ion T₁ (338mM^-1s^-1) and T₂ (133 mM^-1s^-1) relaxivity are due to a cooperative effect contributed by the Mn²⁺ and the Fe₃O₄ crystal. MRI scans of rat brain inoculations show it can be detected in vivo.