Högemann D, Josephson L, Weissleder R, Basilion J P
Center for Molecular Imaging Research, Massachusetts General Hospital, Charlestown, Massachusetts, USA.
Bioconjug Chem. 2000 Nov-Dec;11(6):941-6. doi: 10.1021/bc000079x.
Recently, it has been demonstrated that magnetic resonance imaging (MRI) utilizing monocrystalline iron oxide nanoparticles (MIONs) targeted to an engineered transferrin receptor enables imaging of gene expression. However, the relatively high doses of iron oxides used indicated the need for improved MR imaging probes to monitor changes in gene expression in vivo. Using alternative conjugation chemistries to link targeting ligands and iron oxide nanoparticles, we present the development and characterization as well as improved receptor binding and MRI detection of a novel imaging probe. Iron oxide nanoparticles with a cross-linked dextran coat were conjugated to transferrin (Tf) through the linker molecule N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) to yield Tf-S-S-CLIO. The characteristics of this conjugate were evaluated in comparison to Tf-MION and Tf-CLIO generated by oxidative activation of the dextran-coat with subsequent reduction of Schiff's base. SPDP conjugation allowed approximately a 4-fold increase in the number of Tf molecules attached per iron oxide nanoparticle and resulted in a more than 10-fold improvement of binding and uptake by cells. This translated into an imaging probe that was 16 times better for imaging gene expression in a cellular MRI assay. This novel probe for MRI may substantially increase the sensitivity for the detection of endogenous or genetically induced transferrin receptor expression in small numbers of cells and may significantly reduce the imaging dose from over 100 mg/kg to doses of iron oxides that are currently used in clinical imaging.
最近，已经证明利用靶向工程转铁蛋白受体的单晶氧化铁纳米颗粒（MIONs）的磁共振成像（MRI）能够对基因表达进行成像。然而，所使用的相对高剂量的氧化铁表明需要改进的MR成像探针来监测体内基因表达的变化。通过使用替代的偶联化学方法将靶向配体与氧化铁纳米颗粒连接起来，我们展示了一种新型成像探针的开发、表征以及改善的受体结合和MRI检测性能。具有交联葡聚糖涂层的氧化铁纳米颗粒通过连接分子N-琥珀酰亚胺基3-（2-吡啶二硫基）丙酸酯（SPDP）与转铁蛋白（Tf）偶联，得到Tf-S-S-CLIO。与通过葡聚糖涂层的氧化活化随后还原席夫碱生成的Tf-MION和Tf-CLIO相比，对这种偶联物的特性进行了评估。SPDP偶联使每个氧化铁纳米颗粒连接的Tf分子数量增加了约4倍，并导致细胞结合和摄取提高了10倍以上。这转化为一种成像探针，在细胞MRI分析中对基因表达成像的效果提高了16倍。这种新型的MRI探针可能会大幅提高检测少量细胞中内源性或基因诱导的转铁蛋白受体表达的灵敏度，并可能将成像剂量从超过100mg/kg显著降低到目前临床成像中使用的氧化铁剂量。
