van Everdingen K J, Enochs W S, Bhide P G, Nossiff N, Papisov M, Bogdanov A, Brady T J, Weissleder R
MR Pharmaceutical Program, Massachusetts General Hospital-Nuclear Magnetic Resonance Center, Department of Radiology, Boston 02114.
Radiology. 1994 Nov;193(2):485-91. doi: 10.1148/radiology.193.2.7526413.
To investigate specific surface characteristics of magnetic contrast agents based on a monocrystalline iron oxide nanoparticle (MION) that may determine their uptake and/or transport by axons.
MION were modified to have a range of surface charges or were covalently linked to wheat germ agglutinin (WGA), a neurotropic protein. Each agent was injected directly into the sciatic nerves or femoral arteries of rats (n = 22), and magnetic resonance (MR) images were obtained several days later. The imaging results then were correlated with results at postmortem histologic examination.
Substantial uptake and/or transport by axons occurred only after intraneural injection and only if the agent had a strong surface charge or was covalently linked to WGA. The sciatic nerves appeared as uniformly hypointense structures having lengths proportional to the time from injection to imaging, and the calculated transport rates (4-7 mm/d) were consistent with slow axonal transport. Numerous Schwann cells and macrophages acquired large fractions of the injected agents and contributed substantially to the imaging results.
Those characteristics of MION-based contrast agents that promote efficacy after intraneural injection may impede delivery to the nerve after intraarterial injection.
研究基于单晶氧化铁纳米颗粒（MION）的磁性造影剂的特定表面特性，这些特性可能决定其被轴突摄取和/或运输的情况。
对MION进行修饰，使其具有一系列表面电荷，或与一种嗜神经蛋白麦胚凝集素（WGA）共价连接。将每种造影剂直接注入大鼠（n = 22）的坐骨神经或股动脉，数天后获取磁共振（MR）图像。然后将成像结果与死后组织学检查结果相关联。
仅在神经内注射后，且仅当造影剂具有强表面电荷或与WGA共价连接时，轴突才会大量摄取和/或运输造影剂。坐骨神经表现为均匀的低信号结构，其长度与从注射到成像的时间成正比，计算出的运输速率（4 - 7毫米/天）与缓慢的轴突运输一致。大量施万细胞和巨噬细胞摄取了大部分注入的造影剂，并对成像结果有很大贡献。
基于MION的造影剂在神经内注射后促进效果的那些特性，可能会阻碍动脉内注射后造影剂向神经的递送。
