Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401, USA.
ACS Appl Mater Interfaces. 2011 May;3(5):1502-10. doi: 10.1021/am200075q. Epub 2011 Apr 12.
Gadolinium metal-organic framework (Gd MOF) nanoparticles are an interesting and novel class of nanomaterials that are being studied as a potential replacement for small molecule positive contrast agents in magnetic resonance imaging (MRI). Despite the tremendous interest in these nanoscale imaging constructs, there are limitations, particularly with respect to controlling the particle size, which need to be overcome before these nanoparticles can be integrated into in vivo applications. In an effort to control the size, shape, and size distribution of Gd MOF nanoparticles, hydrotropes were incorporated into the reverse microemulsion synthesis used to produce these nanoparticles. A study of how hydrotropes influenced the mechanism of formation of reverse micelles offered a great deal of information with respect to the physical properties of the Gd MOF nanoparticles formed. Specifically, this study incorporated the hydrotropes, sodium salicylate (NaSal), 5-methyl salicylic acid, and salicylic acid into the reverse microemulsion. Results demonstrated that addition of each of the hydrotropes into the synthesis of Gd MOFs provided a simple route to control the nanoparticle size as a function of hydrotrope concentration. Specifically, Gd MOF nanoparticles synthesized with NaSal showed the best reduction in size distributions in both length and width with percent relative standard deviations being nearly 50% less than nanoparticles produced via the standard route from the literature. Finally, the effect of the size of the Gd MOF nanoparticles with respect to their MRI relaxation properties was evaluated. Initial results indicated a positive correlation between the surface areas of the Gd MOF nanoparticles with the longitudinal relaxivity in MRI. In particular, Gd MOF nanoparticles with an average size of 82 nm with the addition of NaSal, yielded a longitudinal relaxivity value of 83.9 mM⁻¹ [Gd³⁺] sec⁻¹, one of the highest reported values compared to other Gd-based nanoparticles in the literature to date.
钆金属有机骨架（Gd MOF）纳米粒子是一类有趣且新颖的纳米材料，它们被研究作为磁共振成像（MRI）中小分子阳性对比剂的潜在替代品。尽管这些纳米级成像结构引起了极大的兴趣，但仍存在一些限制，特别是在控制粒径方面，这些限制需要克服，才能将这些纳米粒子整合到体内应用中。为了控制 Gd MOF 纳米粒子的尺寸、形状和粒径分布，将增溶剂纳入用于制备这些纳米粒子的反胶束合成中。研究增溶剂如何影响反胶束形成的机制，为形成的 Gd MOF 纳米粒子的物理性质提供了大量信息。具体而言，本研究将增溶剂、水杨酸钠（NaSal）、5-甲基水杨酸和水杨酸纳入反胶束。结果表明，将每种增溶剂添加到 Gd MOF 的合成中，为控制纳米粒子尺寸提供了一种简单的方法，其尺寸可作为增溶剂浓度的函数。具体而言，用 NaSal 合成的 Gd MOF 纳米粒子在长度和宽度的粒径分布上都显示出最好的减小效果，相对标准偏差（percent relative standard deviations）几乎比文献中标准方法制备的纳米粒子小 50%。最后，评估了 Gd MOF 纳米粒子的尺寸对其 MRI 弛豫性能的影响。初步结果表明，Gd MOF 纳米粒子的表面积与其 MRI 中的纵向弛豫率之间存在正相关。特别是，添加 NaSal 的平均尺寸为 82nm 的 Gd MOF 纳米粒子，产生了 83.9mM⁻¹ [Gd³⁺] sec⁻¹的纵向弛豫率值，与迄今为止文献中报道的其他基于 Gd 的纳米粒子相比，这是最高的数值之一。
