Methylated tetra-amide derivatives of paramagnetic complexes for magnetic resonance biosensing with both BIRDS and CEST.
Methylated tetra-amide derivatives of paramagnetic complexes for magnetic resonance biosensing with both BIRDS and CEST.
复制标题
用于 BIRDS 和 CEST 磁共振生物传感的顺磁复合物的甲基化四酰胺衍生物。
DOI：
10.1002/nbm.4687
复制
发表时间：
2022
影响因子：
2.9
通讯作者：
Hyder,Fahmeed
中科院分区：
文献类型：
--
作者：
Zakaria,AbulBM;Huang,Yuegao;Coman,Daniel;Mishra,SandeepK;Mihailovic,JelenaM;Maritim,Samuel;Rojas-Quijano,FedericoA;Jurek,Paul;Kiefer,GarryE;Hyder,Fahmeed
Paramagnetic agents that utilize two mechanisms to provide physiological information by magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) are described. MRI with chemical exchange saturation transfer (CEST) takes advantage of the agent's exchangeable protons (e.g., ‐OH or ‐NHx, where 2 ≥x≥ 1) to create pH contrast. The agent's incorporation of non‐exchangeable protons (e.g., ‐CHy, where 3 ≥y≥ 1) makes it possible to map tissue temperature and/or pH using an MRSI method called biosensor imaging of redundant deviation in shifts (BIRDS). Hybrid probes based upon 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetate chelate (DOTA4−) and its methylated analog (1,4,7,10‐tetraazacyclododecane‐α, α′, α″, α‴‐tetramethyl‐1,4,7,10‐tetraacetate, DOTMA4−) were synthesized, and modified to create new tetra‐amide chelates. Addition of several methyl groups per pendent arm of the symmetrical chelates, positioned proximally and distally to thulium ions (Tm3+), gave rise to favorable BIRDS properties (i.e., high signal‐to‐noise ratio (SNR) from non‐exchangeable methyl proton peaks) and CEST responsiveness (i.e., from amide exchangeable protons). Structures of the Tm3+probes elucidate the influence of methyl group placement on sensor performance. An eight‐coordinate geometry with high symmetry was observed for the complexes:Tm‐L1was based on DOTA4−, whereasTm‐L2andTm‐L3were based on DOTMA4−, where the latter contained an additional carboxylate at the distal end of each arm. The distance of Tm3+from terminal methyl carbons is a key determinant for sustaining BIRDS temperature sensitivity without compromising CEST pH contrast; however, water solubility was influenced by introduction of hydrophobic methyl groups and hydrophilic carboxylate. Combined BIRDS and CEST detection ofTm‐L2, which features two high‐SNR methyl peaks and a strong amide CEST peak, should enable simultaneous temperature and pH measurements for high‐resolution molecular imaging in vivo.
