目的 探讨用超顺磁性氧化铁 (USPIO)螯合唾液酸化酶X(sLeX )形成靶 向内皮细胞粘附分子-1(ELAM-1)的特异 性磁共振成像的分子探针的制备方法， 并研究其物理化学特性。方法 利用物理 沉积方法合成USPIO纳米颗粒，通过疏水 作用，合成较好水溶性的PEG-USPIO，其 表面?COOH充分活化，常温下与sLeX 充分 孵育，超滤离心和去离子水洗涤，形成 磁共振分子探针USPIO-PEG-sLeX ，测定 其表征。结果 透射电镜测定PEG-SPIO平 均粒径为(10±2.6)nm，分散性较好， 大小适宜；动态光散射测定偶联前后其 平均水动力尺寸分别为(34.06±9.95) nm，(53.35±16.99)nm；偶联前后的 PEG化磁性纳米颗粒的Zeta电位分别为 (11.6±3.96)mV，(-12.6±5.33)mV。结 论 化学交联法可成功制备磁共振分子探 针USPIO-PEG-sLeX ，该分子探针具有良好 表征，有望满足体内、外实验特异性结合 ELAM-1的要求。

Objective To investigate the methods of preparing a specific molecular probe for magnetic resonance imaging targeting endothelial cell adhesion molecule-1 (ELAM-1) with ultrasmall superparamagnetic particles of iron oxide(USPIO) chelating sialyl-Lewis X (sLeX), and research its physicochemical properties. Methods Using physical deposition method to synthesis USPIO nanoparticles. By hydrophobic interactions, preferable water-soluble PEG-SPIO was synthesized and the surface -COOH was sufficiently activated,then incubated with sufficient sLeX at room temperature, purified by centrifugal ultrafiltration and washed with deionized water. The magnetic resonance molecular probe USPIO-PEG-sLeX was prepared and characterize it. Results TEM results revealed that the PEG-SPIO had a size of (10±2.6)nm with good dispersibility and suitable size. DLS study showed that before and after coupling,the hydrodynamic mean diameter were (34.06±9.95)nm and (53.35±16.99) nm, respectively. Zeta potential study showed that before and after coupling the potential of PEG conjugated magnetic nanoparticles potential were (11.6±3.96) mV and (-12.6±5.33) mV,respectively. Conclusion The method of chemical conjugation can be successfully prepared MRI molecular probe USPIO-PEGsLeX, which has a well-characterized molecular probe, and it is expected to meet vivo experiments specifically binds to ELAM-1 requirements.