Carboxylic silane-exchanged manganese ferrite nanoclusters with high relaxivity for magnetic resonance imaging

To improve the magnetic properties and MRI contrast effect of Fe O superparamagnetic nanoparticles (NPs), a series of oleate-capped, Mn-doped Mn Fe Fe O (x≤ 0.4) NPs was prepared via a thermal decomposition method and subsequently assembled into nanoclusters by the carboxylic silane. The effects of Mn doping and clustering on the magnetization, relaxivity and contrast enhancement of the Mn Fe Fe O (x≤ 0.4) NPs were studied. Our results revealed that the Mn Fe Fe O NPs exhibited the highest saturation magnetization of 82.55 emu g when x = 0.05. Correspondingly, the assembled Mn Fe Fe O nanoclusters showed the highest relaxivity value of 528 (Mn + Fe) mM s and an enhanced MRI contrast in mouse liver. In addition, the MTT and H&E analysis confirmed that Mn Fe Fe O nanoclusters were non-toxic. Therefore, the biocompatible Mn Fe Fe O nanoclusters with superior relaxometric properties hold great potential in serving as a novel MRI nanoprobe.