Norek Małgorzata, Kampert Erik, Zeitler Uli, Peters Joop A
Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
J Am Chem Soc. 2008 Apr 16;130(15):5335-40. doi: 10.1021/ja711492y.
The transverse 1H relaxivities of aqueous colloidal solutions of dextran coated Dy2O3 nanoparticles of different sizes were investigated at magnetic field strengths (B) between 7 and 17.6 T. The particle size with the maximum relaxivity (r2) appears to vary between 70 nm at 7 T (r2 approximately = 190 s(-1) mM(-1)) and 60 nm at 17.6 T (r2 approximately = 675 s(-1) mM(-1)). A small difference between r2 and r2* was observed, which was ascribed to the effect of the dextran coating. The value of r2 is proportional to B2 up to 12 T after which it saturates. Independent magnetization measurements on these particles at room temperature at magnetic field strengths up to 30 T, however, show a typical paramagnetic behavior with a magnetization of the particle that is proportional to the field strength. The saturation in the curve of r2 as a function of B2 was tentatively explained by the presence of an extremely fast relaxing component of the signal at high field strengths, which is not observable on the NMR time scale. The results of this study can be exploited for the rational design of MRI contrast agents, based on lanthanide oxide particles, with high efficiencies at magnetic field strengths of more than 1.5 T.
在7至17.6 T的磁场强度（B）下，研究了不同尺寸的葡聚糖包被的Dy2O3纳米颗粒水胶体溶液的横向1H弛豫率。弛豫率（r2）最大值对应的粒径似乎在7 T时为70 nm（r2约为190 s(-1) mM(-1)）和17.6 T时为60 nm（r2约为675 s(-1) mM(-1)）之间变化。观察到r2和r2*之间存在微小差异，这归因于葡聚糖包被的影响。r2的值在高达12 T时与B2成正比，之后达到饱和。然而，在室温下对这些颗粒在高达30 T的磁场强度下进行的独立磁化测量显示，颗粒的磁化具有典型的顺磁行为，且与磁场强度成正比。r2随B2变化曲线中的饱和现象初步解释为在高场强下存在信号的极快速弛豫成分，这在NMR时间尺度上无法观察到。本研究结果可用于基于氧化镧系颗粒的MRI造影剂的合理设计，这些造影剂在磁场强度超过1.5 T时具有高效率。
