Bridging the gap between in vitro and in vivo imaging: Isostructural Re and 99mTc complexes for correlating fluorescence and radioimaging studies

Karin A. Stephenson, Sangeeta Ray Banerjee, Travis Besanger, Oyebola O. Sogbein, Murali K. Levadala, Nicole McFarlane, Jennifer A. Lemon, Douglas R. Boreham, Kevin P. Maresca, John D. Brennan, John W. Babich, Jon Zubieta, John F. Valliant

Research output: Contribution to journalArticlepeer-review

179 Scopus citations


A bifunctional ligand that is capable of forming Re and 99mTc complexes as complementary fluorescent and radioactive probes was developed. The tridentate bis(quinoline) amine ligand, which is referred to as the SAACQ system, was prepared in a single step from Fmoc protected lysine in high yield. Reaction of the SAACQ ligand with [Re(CO)3Br3]2- resulted in the formation of the SAACQ-(Re(CO)3)+complex which exhibits favorable fluorescence properties including a long lifetime and a large Stoke's shift. Because the SAACQ ligand is derived from an amino acid, it can readily be linked to or incorporated within peptides as a means of targeting the probe to specific receptors. To demonstrate this feature, the SAACQ ligand and the SAACQ-Re complex were incorporated into fMLFG, a peptide that binds to the formyl peptide receptor (FPR). Uptake of the fMLF[(SAACQ-Re(CO)3)+]G conjugate into human leukocytes in vitro was visualized by fluorescence microscopy, and the observed distribution of the peptide was similar to that of a well-established fluorescent FPR probe. The corresponding Tc complex, fMLF[(SAACQ-99mTc(CO)3)+]G, was prepared in excellent yield from [99mTc(CO)3(OH2)3]+, which affords the opportunity to correlate the results of the microscopy experiments with in vivo radioimaging studies because the probes are isostructural.

Original languageEnglish (US)
Pages (from-to)8598-8599
Number of pages2
JournalJournal of the American Chemical Society
Issue number28
StatePublished - Jul 21 2004

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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