title: RGD-human serum albumin conjugates as efficient tumor targeting probes.
abstract: Cyclic arginine-glycine-aspartate (RGD) peptides and their derivatives have been intensively studied as tumor targeting probes. One major drawback, however, is their short blood circulation half-lives, which greatly compromises their targeting efficacy. To address this issue, a cyclic peptide, c(RGDyK), and an organic dye (IRDye800 or Cy5.5) were covalently conjugated onto human serum albumin (HSA). The conjugates were subjected to in vitro cell staining, in vivo near-infrared fluorescence (NIRF) imaging, ex vivo NIRF imaging, and histologic studies to evaluate their feasibility as tumor imaging probes. As a control, RAD peptide was also coupled with HSA and labeled with IRDye800 for in vivo imaging. The HSA-RGD-IRDye800 exhibited integrin alpha(v)beta(3)-specific binding in cell staining experiment. In vivo NIRF imaging showed higher tumor accumulation and tumor to background contrast of HSA-RGD-IRDye800 over RGD-IRDye800. The integrin specificity of HSA-RGD-IRDye800 is confirmed by both successful inhibition of tumor uptake in the presence of c(RGDyK) and the inability to accumulate in integrin-positive tumors by RAD-HSA-IRDye800. Histologic examination revealed initial tumor vascular binding and eventually both tumor vasculature and tumor cell integrin binding in vivo. In summary, we successfully developed an RGD-based protein conjugate with prolonged circulation half-life for NIRF imaging of tumor integrin alpha(v)beta(3) expression. The success of this study may be generalizable for other peptide-based probes to be conjugated with HSA for prolonged tumor contrast and improved pharmacokinetics.
authors.affiliation: Molecular Imaging Program at Stanford, Department of Radiology and Bio-X Program, Stanford University School of Medicine, Standford, CA 94305-5484, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Chen
authors.forename: Jin
authors.initials: J
authors.lastname: Xie
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D002232:Carbocyanines / Q000378:metabolism; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D006207:Half-Life; D006651:Histocytochemistry; D006801:Humans; D007211:Indoles / Q000378:metabolism; D039302:Integrin alphaVbeta3 / Q000032:analysis* / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D015336:Molecular Probe Techniques; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology*; D010456:Peptides, Cyclic / Q000097:blood / Q000378:metabolism; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D019265:Spectroscopy, Near-Infrared; D014018:Tissue Distribution
chemical_list: C098793:CY5.5 cyanine dye; D002232:Carbocyanines; C427728:IRDye800; D007211:Indoles; D039302:Integrin alphaVbeta3; D010456:Peptides, Cyclic; D012709:Serum Albumin; C507169:cyclic arginine-glycine-aspartic acid peptide