Synthesis and evaluation of two NIR fluorescent cyclic RGD penta-peptides for targeting integrins

Yunpeng Ye, Sharon Bloch, Baogang Xu, Samuel Achilefu

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Interest in novel RGD peptides has been increasingly growing as the interactions between RGD peptides and integrins are the basis for a variety of cellular functions and medical applications such as modulation of cell adhesion, invasion, tumor angiogenesis, and metastasis. In particular, we have been interested in novel NIR fluorescent RGD peptides as potential optical contrast agents for in vivo tumor optical imaging. Therefore, two cyclic RGD penta-peptides conjugated with a NIR fluorescent carbocyanine (Cypate), i.e. lactam-based cyclo[RGDdK(Cypate)] (1) and disulfide-containing Cypate-cyclo(CRGBC)-NH2 (2), were designed and synthesized. The competitive binding assay between the purified αvβ 3 integrin and the peptide ligands using 125I-echistatin as a tracer showed that 1 had a higher receptor binding affinity (IC 50∼10-7 M) than 2 (1C50∼10-6 M). Furthermore, the internalization of l in A549 cells in vitro was less than 2, as revealed by fluorescence microscopy. These results suggest that both the lactam- and disulfide-based cyclic RGB penta-peptides should be further studied structurally and functionally to elucidate the advantages of each class of compounds.

Original languageEnglish (US)
Title of host publicationProgress in Biomedical Optics and Imaging - Proceedings of SPIE
StatePublished - 2006
Externally publishedYes
EventOptical Molecular Probes for Biomedical Applications - San Jose, CA, United States
Duration: Jan 22 2006Jan 24 2006

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceOptical Molecular Probes for Biomedical Applications
Country/TerritoryUnited States
CitySan Jose, CA


  • Cellular internalization
  • Cyclic penta-peptide
  • Cypate
  • Disulfide cyclization
  • Integrin receptors
  • Lactam cyclization
  • NIR fluorescent probe
  • Optical imaging
  • Receptor binding
  • RGB peptides

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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