Acid-catalyzed proton exchange as a novel approach for relaxivity enhancement in Gd-HPDO3A-like complexes.

Chemical Science
Loredana LeoneLorenzo Tei

Abstract

A current challenge in medical diagnostics is how to obtain high MRI relaxation enhancement using GdIII-based contrast agents (CAs) containing the minimum concentration of GdIII ions. We report that in GdHPDO3A-like complexes a primary amide group located in close proximity to the coordinated hydroxyl group can provide a strong relaxivity enhancement at slightly acidic pH. A maximum relaxivity of r1 = 9.8 mM-1 s-1 (20 MHz, 298 K) at acidic pH was achieved, which is more than double that of clinically approved MRI contrast agents under identical conditions. This effect was found to strongly depend on the number of amide protons, i.e. it decreases with a secondary amide group and almost completely vanishes with a tertiary amide. This relaxivity enhancement is attributed to an acid-catalyzed proton exchange process between the metal-coordinated OH group, the amide protons and second sphere water molecules. The mechanism and kinetics of the corresponding H+ assisted exchange process are discussed in detail and a novel simultaneous double-site proton exchange mechanism is proposed. Furthermore, 1H and 17O NMR relaxometry, Chemical Exchange Saturation Transfer (CEST) on the corresponding EuIII complexes, and thermodynamic and kinetic...Continue Reading

References

Mar 31, 2005·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Donald E WoessnerA Dean Sherry
Oct 1, 1982·Talanta·R Delgado, J J da Silva
Feb 18, 2011·Angewandte Chemie·Daniela Delli CastelliSilvio Aime
Apr 12, 2017·Angewandte Chemie·Eszter BorosPeter Caravan
Oct 24, 2018·Chemical Reviews·Jessica WahsnerPeter Caravan
Jan 9, 2019·Chemistry : a European Journal·Giuseppe FerrautoLorenzo Tei

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Citations

Apr 29, 2021·Dalton Transactions : an International Journal of Inorganic Chemistry·Loredana LeoneLorenzo Tei

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Methods Mentioned

BETA
Chemical Exchange
O

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