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Antiferromagnetic Iron Nanocolloids: A New Generation in Vivo T1 MRI Contrast Agent

Peng, Yung-Kang, Liu, Chien-Liang, Chen, Hsieh-Chih, Chou, Shang-Wei, Tseng, Wei-Hsuan, Tseng, Yu-Jui, Kang, Chia-Cheng, Hsiao, Jong-Kai, Chou, Pi-Tai
Journal of the American Chemical Society 2013 v.135 no.49 pp. 18621-18628
biocompatibility, biodegradability, emus, ferrimagnetic materials, goethite, image analysis, iron, iron oxides, kidneys, liver, nanocomposites, nanoparticles, porous media, silica
A novel T₁ agent, antiferromagnetic α-iron oxide-hydroxide (α-FeOOH) nanocolloids with a diameter of 2–3 nm, has been successfully prepared. These nanocolloids, together with a post synthetic strategy performed in mesoporous silica, are a great improvement over the low T₁-weighted contrast common in traditional magnetic silica nanocomposites. The intrinsic antiferromagnetic goethite (α-FeOOH) shows very low magnetization (Mz) of 0.05 emu g–¹ at H = 2 T at 300 K (0.0006 emu g–¹ for FeOOH/WMSN-PEG), which is 2 orders of magnitude smaller than any current ultrasmall iron oxide NPs (>5 emu g–¹) reported to date, hence ensuring the low r₂ (∝ Mz) (7.64 mM–¹ s–¹) and r₂/r₁ ratio (2.03) at 4.7 T. These biodegradable α-FeOOH nanocolloids also demonstrate excellent in vitro cellular imaging and in vivo MR vascular and urinary trace imaging capability with outstanding biocompatibility, which is exceptionally well secreted by the kidney and not the liver as with most nanoparticles, opening up a new avenue for designing powerful antiferromagnetic iron T₁ contrast agents.