Inert macrocyclic Eu3+ complex with affirmative paraCEST features,Inorganic Chemistry Frontiers

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Inert macrocyclic Eu3+ complex with affirmative paraCEST features
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2020-03-16 , DOI: 10.1039/c9qi01612k
Tanja Gambino _{1,

2,

3,

4} , Laura Valencia _{5,

6,

7,

8,

9} , Paulo Pérez-Lourido _{5,

6,

7,

8,

9} , David Esteban-Gómez _{9,

10,

11,

12,

13} , Moritz Zaiss _{2,

3,

4,

14,

15} , Carlos Platas-Iglesias _{9,

10,

11,

12,

13} , Goran Angelovski _{1,

2,

3,

4}

Affiliation

We report on a macrocyclic platform based on an 18-membered macrocycle that forms kinetically highly inert paramagnetic complexes and possesses an excellent outlook for the development of bioresponsive paraCEST (paramagnetic chemical exchange saturation transfer) contrast agents. The investigated europium(III) chelate is non-hydrated and contains four amide groups, each possessing two paramagnetically shifted proton resonances distant from bulk water. The X-ray crystal structure and solution studies indicate that the metal ion is ten-coordinated, being directly bound to the six N atoms of the macrocycle and the four amide O atoms of the pendant arms. The complex presents an excellent inertness with respect to dissociation, being stable under a variety of harsh conditions, including highly acidic and basic media or elevated temperatures. The amide protons are in slow-to-intermediate exchange with bulk water, which gives rise to the generation of a strong CEST effect at low probe concentration and saturation powers (∼25% at 5 mM, B₁ = 5 μT, 37 °C). We demonstrate the potential of this platform for mapping pH in its microenvironment and foresee potential for the development of diverse paraCEST probes and sensors.

中文翻译：

具有肯定paraCEST特征的惰性大环Eu3 +配合物

我们在一个基于18元大环的大环平台上进行了报道，该大环形成了动力学上高度惰性的顺磁性复合物，并且对生物响应性paraCEST（顺磁性化学交换饱和转移）造影剂的发展具有极好的前景。所研究的铕（III螯合物是非水合的，包含四个酰胺基，每个酰胺基均具有两个顺磁位移的质子共振，远离大量水。X射线晶体结构和溶液研究表明，金属离子是十配位的，直接与大环的六个N原子和侧链的四个酰胺O原子结合。该络合物在解离方面表现出出色的惰性，在各种苛刻条件下（包括高酸性和碱性介质或高温）均稳定。酰胺质子与大量水缓慢-中间交换，这在低探针浓度和饱和功率下（5 mM时约为25％，B _1）产生了强大的CEST效应。= 5μT，37°C）。我们展示了该平台在微环境中绘制pH值的潜力，并预见了开发各种paraCEST探针和传感器的潜力。

更新日期：2020-03-16

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