title: Detection of vascular adhesion molecule-1 expression using a novel multimodal nanoparticle.
abstract: Endothelial vascular adhesion molecule-1 (VCAM-1) is a critical component of the leukocyte-endothelial adhesion cascade, and its strict temporal and spatial regulation make it an ideal target for imaging and therapy. The goal of this study was to develop novel VCAM-1-targeted imaging agents detectable by MRI and fluorescence imaging using phage display-derived peptide sequences and multimodal nanoparticles (NPs). We hypothesized that VCAM-1-mediated cell internalization of phage display-selected peptides could be harnessed as an amplification strategy to chaperone and trap imaging agents inside VCAM-1-expressing cells, thus improving target-to-background ratios. To accomplish our goal, iterative phage display was performed on murine endothelium under physiological flow conditions to identify a family of VCAM-1-mediated cell-internalizing peptides. One specific sequence, containing the VHSPNKK motif that has homology to the alpha-chain of very late antigen (a known ligand for VCAM-1), was shown to bind VCAM-1 and block leukocyte-endothelial interactions. Compared with VCAM-1 monoclonal antibody, the peptide showed 12-fold higher target-to-background ratios. A VHSPNKK-modified magnetofluorescent NP (VNP) showed high affinity for endothelial cells expressing VCAM-1 but surprisingly low affinity for macrophages. In contrast, a control NP without VCAM-1-targeting sequences showed no affinity for endothelial cells. In vivo, VNP successfully identified VCAM-1-expressing endothelial cells in a murine tumor necrosis factor-alpha-induced inflammatory model and colocalized with VCAM-1-expressing cells in atherosclerotic lesions present in cholesterol-fed apolipoprotein E apoE-/- mice. These results indicate that: (1) small peptide sequences can significantly alter targeting of NPs, (2) the used amplification strategy of internalization results in high target-to-background ratios, and (3) this technology is useful for in vivo imaging of endothelial markers.
authors.affiliation: Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Kelly
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Allport
authors.forename: Andrew
authors.initials: A
authors.lastname: Tsourkas
authors.forename: Vivek R
authors.initials: VR
authors.lastname: Shinde-Patil
authors.forename: Lee
authors.initials: L
authors.lastname: Josephson
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency; D001161:Arteriosclerosis / Q000473:pathology; D002478:Cells, Cultured; D004423:Ear / Q000033:anatomy & histology / Q000098:blood supply; D042783:Endothelial Cells / Q000737:chemistry / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000378:metabolism; D008168:Lung / Q000166:cytology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008280:Magnetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008832:Microchemistry / Q000379:methods*; D018613:Microscopy, Confocal / Q000379:methods; D009206:Myocardium / Q000166:cytology; D049329:Nanostructures / Q000032:analysis* / Q000737:chemistry; D019151:Peptide Library; D010455:Peptides / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D019151:Peptide Library; D010455:Peptides; D019010:Vascular Cell Adhesion Molecule-1; D016650:Fluorescein-5-isothiocyanate