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首页> 外文期刊>Chemistry: A European journal >Gd (DTPA-bisamide) alkyl Copolymers: A Hint for the Formation of MRI Contrast Agents with Very High Relaxivity
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Gd (DTPA-bisamide) alkyl Copolymers: A Hint for the Formation of MRI Contrast Agents with Very High Relaxivity

机译：Gd（DTPA-双酰胺）烷基共聚物：具有很高弛豫度的MRI造影剂形成的提示

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摘要

A variable-temperature, multiple-field ~(17)O NMR and EPR spectroscopic study has been performed on three Gd (DTPA-bisamide) alkyl copolymers, [Gd (DTPA-BA)-(CH_2)_n]_x (n=6, 10, 12; DTPA= diethylenetriamine-N, N, N', N", N"'-pentaacetate). The rate and mechanism of water exchange is identical for the polymer complexes and [Gd(DTPA-BMA)(H_2O)], which can be considered as the monomer unit of the polymers. Transverse electronic relaxation rates, measured by EPR, increase with increasing rotational correlation time. Rigid intramolecular micellelike structures form in aqueous solutions of the Gd(DTPA-bisamide) alkyl copolymers. Consequently, the longitudinal ~(17)O relaxation rates for [Gd(DTPA-BA)-(CH_2)_(10)]_x and [Gd(DTPA-BA)-(CH_2)_(12)]_x, were interpreted with the Lipari-Szabo treatment. This involves the inclusion of a global correlation time, representing the motion of the whole micellelike association, and a local correlation time, representing the motion of the Gd-O vector. The global correlation time obtained for the two polymers reflects the ratio of the molecular weights, whereas the local correlation times and the general order parameters are similar for both copolymers. The proton relaxivity difference can be explained by the different global correlation times. Thus, contrary to linear polymers in general, for the present polymers the global motion significantly contributes to relaxivity. Relaxivity is limited by water exchange; simulations show that proton relaxivities over 100 mM~(-1)s(-1) could be obtained by substituting the Gd (DTPA-bisamide) units with a gadolinium chelate with fast water exchange.
机译：对三种Gd（DTPA-双酰胺）烷基共聚物[Gd（DTPA-BA）-（CH_2）_n] _x（n = 6）进行了温度可变的多场〜（17）O NMR和EPR光谱研究，10、12; DTPA ＝二亚乙基三胺-N，N，N'，N”，N”'-五乙酸酯。对于聚合物络合物和[Gd（DTPA-BMA）（H_2O）]，水交换的速率和机理是相同的，可以将其视为聚合物的单体单元。通过EPR测量的横向电子弛豫率随旋转相关时间的增加而增加。在Gd（DTPA-双酰胺）烷基共聚物的水溶液中形成刚性的分子内胶束状结构。因此，解释了[Gd（DTPA-BA）-（CH_2）_（10）] _ x和[Gd（DTPA-BA）-（CH_2）_（12）] _ x的纵向〜（17）O弛豫率。 Lipari-Szabo治疗。这涉及包括代表整个胶束状缔合运动的全局关联时间和代表Gd-O矢量运动的局部关联时间。两种聚合物获得的整体相关时间反映了分子量的比率，而两种共聚物的局部相关时间和一般顺序参数相似。质子弛豫率差异可以用不同的全局相关时间来解释。因此，与通常的线性聚合物相反，对于本发明的聚合物，整体运动显着有助于松弛。放松受到水交换的限制;模拟表明，用fast螯合物快速交换水来取代Gd（DTPA-双酰胺）单元，可以获得100 mM〜（-1）s（-1）以上的质子弛豫。

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