Relaxometry, Luminescence Measurements, Electrophoresis, and Animal Biodistribution of Lanthanide(III) Complexes of Some Polyaza Macrocyclic Acetates Containing Pyridine

Won D. Kim, Garry E. Kiefer, Frédéric Maton, Kenneth McMillan, Robert N. Muller, A. Dean Sherry

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Four Gd3+ complexes [Gd(BP2A)+, Gd(PC2A)+, Gd(PCTA)0, and Gd(BP04A)] with polyazamacrocyclic ligands that contain a pyridine moiety were prepared and examined for possible use as MRI contrast enhancement agents. We estimated the number of inner sphere water molecules (qGd) for the Gd3+ complexes from the values of q found for the Tb3+ and/or Eu3+ complexes by luminescence lifetime measurements. We have estimated that qod = 3.5, 3.3, 2.4, and 0.2 for Gd(BP2A)+, Gd(PC2A)+, Gd(PCTA)0, and Gd(BPO4A), respectively. The inner sphere relaxivities (r1,inner) of these tetraaza macrocyclic complexes were higher than that of Gd(DOTA) [i.e. 6.79 for Gd(BP2A)+,6.21 for Gd(PC2A)+, and 4.60 for Gd(PCTA)0 mM- 1s−1 at 40 MHz and 25 °C], but the normalized relaxivities per qGd (1.94, 1.88, and 1.92 mM−1 s−1, respectively) were comparable to that of Gd(DOTA). A quantitative treatment of the NMRD profiles based on Solomon-Bloembergen-Morgan theory, using the NMRD profile of Gd(BP04A) to correct for an outer sphere contribution, showed that the complexes exhibit characteristics similar to that of Gd(DOTA) but with shorter electronic relaxation times. Tissue biodistribution results using radioactive 153Sm and 159Gd complexes in rats indicate that the cationic [153Sm-(BP2A)+ and 153Sm(PC2A)+] complexes accumulate preferably in the bone tissue while the neutral [153Sm-(PCTA)0] and anionic [153Sm(BP04A)] complexes appear to have renal clearances similar to those of other low molecular weight contrast agents [i.e. Gd(DTPA)2− and Gd(DOTA)].

Original languageEnglish (US)
Pages (from-to)2233-2243
Number of pages11
JournalInorganic Chemistry
Issue number8
StatePublished - Apr 1 1995


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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