Department of Energy, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Phys Chem Chem Phys. 2021 Aug 12;23(31):16948-16957. doi: 10.1039/d1cp00708d.
The anomalous behavior of confined water at the nanoscale has remarkable implications in a number of nanotechnological applications. In this work, we analyze the effect of water self-diffusion on the dynamic properties of a solvated gadolinium-based paramagnetic complex, typically used for contrast enhancement in magnetic resonance imaging. In particular, we examine the effect of silica-based nanostructures on water behavior in the proximity of the paramagnetic complex via atomistic simulations, and interpret the resulting tumbling dynamics in the light of the local solvent modification based on the Lipari-Szabo formalism and of the fractional Stokes-Einstein relation. It is found that the local water confinement induces an increased "stiffness" on the outer sphere of the paramagnetic complex, which eventually reduces its tumbling properties. These model predictions are found to explain well the relaxivity enhancement observed experimentally by confining paramagnetic complexes into porous nanoconstructs, and thus offer mechanistic guidelines to design improved contrast agents for imaging applications.
受限水在纳米尺度上的异常行为在许多纳米技术应用中具有重要意义。在这项工作中，我们分析了水自扩散对水合镝基顺磁配合物动态特性的影响，该配合物通常用于磁共振成像中的对比增强。具体来说，我们通过原子模拟研究了基于二氧化硅的纳米结构对顺磁配合物附近水行为的影响，并根据 Lipari-Szabo 形式主义和分数 Stokes-Einstein 关系，根据局部溶剂修饰解释了由此产生的翻滚动力学。结果表明，局部水限制导致顺磁配合物外球的“刚度”增加，最终降低了其翻滚性能。这些模型预测很好地解释了将顺磁配合物限制在多孔纳米结构中实验观察到的弛豫增强，从而为设计用于成像应用的改进对比剂提供了机制指导。
