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

To improve the magnetic properties and MRI contrast effect of Fe3O4 superparamagnetic nanoparticles (NPs), a series of oleate-capped, Mn-doped MnxFe(1-x)Fe2O4 (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 MnxFe(1-x)Fe2O4 (x <= 0.4) NPs were studied. Our results revealed that the MnxFe(1-x)Fe2O4 NPs exhibited the highest saturation magnetization of 82.55 emu g(-1) when x - 0.05. Correspondingly, the assembled MnxFe(1-x)Fe2O4 nanoclusters showed the highest relaxivity value of 528 (Mn + Fe) mM(-1) s(-1) and an enhanced MRI contrast in mouse liver. In addition, the MTT and H&E analysis confirmed that MnxFe(1-x)Fe2O4 nanoclusters were non-toxic. Therefore, the biocompatible Mn0.05Fe(1-0.05)Fe2O4 nanoclusters with superior relaxometric properties hold great potential in serving as a novel MRI nanoprobe.