World Class University Program of Chemical Convergence for Energy & Environment, and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea.
J Am Chem Soc. 2011 Aug 17;133(32):12624-31. doi: 10.1021/ja203340u. Epub 2011 Jul 25.
Uniform and extremely small-sized iron oxide nanoparticles (ESIONs) of < 4 nm were synthesized via the thermal decomposition of iron-oleate complex in the presence of oleyl alcohol. Oleyl alcohol lowered the reaction temperature by reducing iron-oleate complex, resulting in the production of small-sized nanoparticles. XRD pattern of 3 nm-sized nanoparticles revealed maghemite crystal structure. These nanoparticles exhibited very low magnetization derived from the spin-canting effect. The hydrophobic nanoparticles can be easily transformed to water-dispersible and biocompatible nanoparticles by capping with the poly(ethylene glycol)-derivatized phosphine oxide (PO-PEG) ligands. Toxic response was not observed with Fe concentration up to 100 μg/mL in MTT cell proliferation assay of POPEG-capped 3 nm-sized iron oxide nanoparticles. The 3 nm-sized nanoparticles exhibited a high r(1) relaxivity of 4.78 mM(-1) s(-1) and low r(2)/r(1) ratio of 6.12, demonstrating that ESIONs can be efficient T(1) contrast agents. The high r(1) relaxivities of ESIONs can be attributed to the large number of surface Fe(3+) ions with 5 unpaired valence electrons. In the in vivo T(1)-weighted magnetic resonance imaging (MRI), ESIONs showed longer circulation time than the clinically used gadolinium complex-based contrast agent, enabling high-resolution imaging. High-resolution blood pool MR imaging using ESIONs enabled clear observation of various blood vessels with sizes down to 0.2 mm. These results demonstrate the potential of ESIONs as T(1) MRI contrast agents in clinical settings.
通过在油醇存在下热分解油酸铁配合物，合成了尺寸小于 4nm 的均一且极小的氧化铁纳米粒子（ESIONs）。油醇通过还原油酸铁配合物降低了反应温度，从而产生了小尺寸的纳米粒子。3nm 尺寸的纳米粒子的 XRD 图谱显示出磁铁矿晶体结构。这些纳米粒子表现出非常低的磁化强度，源于自旋倾斜效应。通过用聚（乙二醇）衍生的膦氧化物（PO-PEG）配体进行封端，疏水纳米粒子可以很容易地转化为水分散性和生物相容性的纳米粒子。在 MTT 细胞增殖测定中，用 PO-PEG 封端的 3nm 尺寸的氧化铁纳米粒子的铁浓度高达 100μg/mL 时，没有观察到毒性反应。3nm 尺寸的纳米粒子表现出高 r(1)弛豫率为 4.78mM(-1)s(-1)和低 r(2)/r(1)比值为 6.12，表明 ESIONs 可以作为高效 T(1)对比剂。ESIONs 的高 r(1)弛豫率可归因于具有 5 个未配对价电子的大量表面 Fe(3+)离子。在体内 T(1)加权磁共振成像（MRI）中，ESIONs 显示出比临床使用的基于钆配合物的对比剂更长的循环时间，从而实现高分辨率成像。使用 ESIONs 的高分辨率血池 MRI 能够清晰观察到各种尺寸小至 0.2mm 的血管。这些结果表明 ESIONs 作为 T(1)MRI 对比剂在临床环境中的潜力。
