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Lanthanide-Based T2ex and CEST Complexes Provide Insights into the Design of pH Sensitive MRI Agents.

Authors
  • Zhang, Lei1
  • Martins, André F1, 2
  • Zhao, Piyu1
  • Wu, Yunkou2
  • Tircsó, Gyula3
  • Sherry, A Dean1, 2
  • 1 Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 West Campbell Road, Richardson, TX, 75080, USA.
  • 2 Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390, USA.
  • 3 Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetemtér 1, 4010, Debrecen, Hungary. , (Hungary)
Type
Published Article
Journal
Angewandte Chemie International Edition in English
Publisher
Wiley (John Wiley & Sons)
Publication Date
Dec 22, 2017
Volume
56
Issue
52
Pages
16626–16630
Identifiers
DOI: 10.1002/anie.201707959
PMID: 29024242
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

The CEST and T1 /T2 relaxation properties of a series of Eu3+ and Dy3+ DOTA-tetraamide complexes with four appended primary amine groups are measured as a function of pH. The CEST signals in the Eu3+ complexes show a strong CEST signal after the pH was reduced from 8 to 5. The opposite trend was observed for the Dy3+ complexes where the r2ex of bulk water protons increased dramatically from ca. 1.5 mm-1 s-1 to 13 mm-1 s-1 between pH 5 and 9 while r1 remained unchanged. A fit of the CEST data (Eu3+ complexes) to Bloch theory and the T2ex data (Dy3+ complexes) to Swift-Connick theory provided the proton-exchange rates as a function of pH. These data showed that the four amine groups contribute significantly to proton-catalyzed exchange of the Ln3+ -bound water protons even though their pKa 's are much higher than the observed CEST or T2ex effects. This demonstrated the utility of using appended acidic/basic groups to catalyze prototropic exchange for imaging tissue pH by MRI. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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