Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents
Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents
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DOI：
10.1021/nl071099b
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发表时间：
2007-08-01
期刊：
影响因子：
10.8
通讯作者：
Weller, Horst
中科院分区：
文献类型：
--
作者：
Tromsdorf, Ulrich I.;Bigall, Nadja C.;Weller, Horst
在高沸点乙醚溶剂中合成了不同尺寸的超顺磁性 MnFe2O4 纳米晶体，并使用三种不同的方法将其转移到水中。首先，我们应用配体交换以形成水溶性聚合物壳。其次，将颗粒嵌入两亲性聚合物壳中。第三，纳米颗粒被嵌入由脂质形成的大胶束中。尽管所有方法都会导致有效的负对比度增强，但我们观察到这种效果的程度存在显着差异。与使用相同尺寸纳米颗粒的聚合物涂覆颗粒相比，胶束系统的横向弛豫率，特别是 r(2)* 要高得多。我们还观察到，聚合物涂覆的纳米晶体的横向弛豫率随着粒径的增加而增加。结果与描述弛豫率对磁球尺寸的依赖性的理论模型进行了定性比较。
Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r(2)*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres.