A pH-Responsive MRI Agent that Can Be Activated beyond the Tissue Magnetization Transfer Window

Xiaojing Wang, Yunkou Wu, Todd C. Soesbe, Jing Yu, Piyu Zhao, Garry E. Kiefer, A. Dean Sherry

Research output: Contribution to journalArticle

16 Scopus citations


A terbium-based complex that displays a water exchange CEST resonance well outside the normal magnetization transfer (MT) frequency range of tissues provides a direct readout of pH values by MRI. Deprotonation of the phenolic proton in this complex results in a frequency shift of 56 ppm in a bound water molecule exchange peak between pH 5 and 8. This allows direct imaging of pH without prior knowledge of the agent concentration and with essentially no interference from the tissue MT signal. Imaging beyond the MT effect: A pH-responsive MRI contrast agent displays a water exchange peak near -550 ppm, well outside the magnetization transfer (MT) window. Additionally, the chemical shift of 56 ppm in this CEST peak is quite sensitive to changes in pH. These features enable direct imaging of pH in vivo with no masking effect from the inherent tissue MT signal.

Original languageEnglish (US)
Pages (from-to)8662-8664
Number of pages3
JournalAngewandte Chemie - International Edition
Issue number30
StatePublished - Jul 20 2015



  • imaging agents
  • lanthanides
  • magnetic resonance imaging
  • magnetization transfer
  • paraCEST

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis

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