64Cu-labeled LyP-1-dendrimer for PET-CT imaging of atherosclerotic plaque

Jai Seo, Hyounggee Baek, Lisa M. Mahakian, Jiro Kusunose, Juliana Hamzah, Erkki Ruoslahti, Katherine W. Ferrara

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

The ability to detect and quantify macrophage accumulation can provide important diagnostic and prognostic information for atherosclerotic plaque. We have previously shown that LyP-1, a cyclic 9-amino acid peptide, binds to p32 proteins on activated macrophages, facilitating the visualization of atherosclerotic plaque with PET. Yet, the in vivo plaque accumulation of monomeric [18F]FBA-LyP-1 was low (0.31 ± 0.05%ID/g). To increase the avidity of LyP-1 constructs to p32, we synthesized a dendritic form of LyP-1 on solid phase using lysine as the core structural element. Imaging probes (FAM or 6-BAT) were conjugated to a lysine or cysteine on the dendrimer for optical and PET studies. The N-terminus of the dendrimer was further modified with an aminooxy group in order to conjugate LyP-1 and ARAL peptides bearing a ketone. Oxime ligation of peptides to both dendrimers resulted in (LyP-1)4- and (ARAL)4-dendrimers with optical (FAM) and PET probes (6-BAT). For PET-CT studies, (LyP-1)4- and (ARAL) 4-dendrimer-6-BAT were labeled with 64Cu (t1/2 = 12.7 h) and intravenously injected into the atherosclerotic (ApoE -/-) mice. After two hours of circulation, PET-CT coregistered images demonstrated greater uptake of the (LyP-1)4-dendrimer- 64Cu than the (ARAL)4-dendrimer-64Cu in the aortic root and descending aorta. Ex vivo images and the biodistribution acquired at three hours after injection also demonstrated a significantly higher uptake of the (LyP-1)4-dendrimer-64Cu (1.1 ± 0.26%ID/g) than the (ARAL)4-dendrimer-64Cu (0.22 ± 0.05%ID/g) in the aorta. Similarly, subcutaneous injection of the LyP-1-dendrimeric carriers resulted in preferential accumulation in plaque-containing regions over 24 h. In the same model system, ex vivo fluorescence images within aortic plaque depict an increased accumulation and penetration of the (LyP-1)4-dendrimer-FAM as compared to the (ARAL)4-dendrimer-FAM. Taken together, the results suggest that the (LyP-1)4-dendrimer can be applied for in vivo PET imaging of plaque and that LyP-1 could be further exploited for the delivery of therapeutics with multivalent carriers or nanoparticles.

Original languageEnglish (US)
Pages (from-to)231-239
Number of pages9
JournalBioconjugate Chemistry
Volume25
Issue number2
DOIs
StatePublished - Feb 19 2014

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Organic Chemistry
  • Pharmaceutical Science
  • Biomedical Engineering
  • Pharmacology

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