Amino-grafted water-soluble ferrimagnetic iron oxide nanoparticles with ultra-high relaxivity for dual-modal magnetic resonance imaging

Highly stable dispersion is an important precondition for functionalized magnetic nanoparticles used as a contrast agent. Amino-grafted ferromagnetic γ-Fe2O3 nanoparticles are synthesized by deep-eutectic-solvent electrolysis for magnetic resonance imaging. The statistical naked scale of the particle is 8.2 nm with a magnetization of 71.9 emu g−1. An ultra-high Zeta potential of + 50 mV boosts the dispersion stable for more than 600 days, which is unprecedented. The 26.4 nm hydrated nanoparticles exhibit high biocompatibility after being efficiently ingested by cells in vitro. Both longitudinal relaxation efficiency of 179.7 mM−1 s−1 and transverse relaxivity of 497.8 mM−1 s−1 are among the highest demonstrated in recent years. Whether in vitro or in vivo, the imaging mode changes from T1 to T2 with the increase of iron equivalent. At doses 0.12 and 0.91 mg Fe per kg living body, the nanoparticles are capable of prominently weighted imaging of T1 and T2 of the liver, respectively. The nanocrystals can significantly distinguish between normal tissue and the tumor site of the liver as well. Findings demonstrate that the highly stable dispersion of amino-grafted ferrimagnetic nanoparticles is capable of dual-modal magnetic resonance imaging with high relaxation efficiency and significant resolution.