Gd@C60[C(COOH)2]10 and Gd@C60(OH)x:: Nanoscale aggregation studies of two metallofullerene MRI contrast agents in aqueous solution
Gd@C60[C(COOH)2]10 and Gd@C60(OH)x:: Nanoscale aggregation studies of two metallofullerene MRI contrast agents in aqueous solution
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DOI：
10.1021/nl0485713
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发表时间：
2004-12-01
期刊：
影响因子：
10.8
通讯作者：
Wilson, LJ
中科院分区：
文献类型：
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作者：
Sitharaman, B;Bolskar, RD;Wilson, LJ
衍生的水溶性Gd基金属富勒烯是优异的MRI造影剂，对于没有直接Gd-OH 2键合的试剂具有异常大的质子弛豫率。在这项研究中，动态光散射（DLS），静态光散射（SLS）和透射电子显微镜（TEM）已被用来表征两个这样的物种，Gd@C-60[C（COOH）（2）]（10）和Gd@C-60（OH）（x），在水溶液中聚集的倾向，因为已知聚集通过增加它们的旋转相关时间（通过更缓慢地翻滚聚集体）来增强MRI造影剂的质子弛豫率。本聚集研究已经作为浓度、温度和pH的函数进行，并且已经揭示了两种化合物在pH = 9下聚集以形成具有30和90 nm之间的尺寸的球形和不规则簇，几乎没有浓度或温度依赖性。在pH = 9以下，聚集体尺寸稳定且显著地增加，在pH = 5时达到600-1000 nm的流体动力学直径。此外，Gd@C-60[C（COOH）（2）]的聚集体结合在一起的分子间力比Gd@C-60（OH）（x）弱。我们的结论是，这些金属富勒烯物种在水溶液中自组装成纳米级聚集体的趋势可能会产生异常大的，外层，pH敏感的质子弛豫。
Derivatized water-soluble Gd-based metallofullerenes are excellent MRI contrast agents with unusually large proton relaxivities for agents with no direct Gd-OH2 bonding. In this study, dynamic light scattering (DLS), static light scattering (SLS), and transmission electron microscopy (TEM) have been used to characterize the propensity of two such species, Gd@C-60[C(COOH)(2)](10) and Gd@C-60(OH)(x), to aggregate in aqueous solution, since aggregation is known to enhance proton relaxivities of MRI contrast agents by increasing their rotational correlation times (via more slowly tumbling aggregates). The present aggregation study has been conducted as a function of concentration, temperature, and pH and has revealed that both compounds aggregate at pH = 9 to form spherical and irregular clusters having sizes between 30 and 90 nm, with little concentration or temperature dependency. Below pH = 9, the aggregate sizes increase steadily and dramatically, reaching hydrodynamic diameters of 600-1000 nm by pH = 5. Additionally, the intermolecular forces holding the aggregates together are weaker for Gd@C-60[C(COOH)(2)] than for Gd@C-60(OH)(x). We conclude that the tendency of these metallofullerene species to self-assemble into nanoscale aggregates in aqueous solution likely produces their unusually large, outer-sphere, pH-sensitive proton relaxivities.