title: SPECT imaging of fibrin using fibrin-binding peptides.
abstract: Noninvasive detection of fibrin in vivo using diagnostic imaging modalities may improve clinical decision-making on possible therapeutic options in atherosclerosis, cancer and thrombus-related pathologies such as pulmonary embolism and deep venous thrombosis. The aim of this study was to assess the potential of a novel (111)In-labeled fibrin-binding peptide (FibPep) to visualize thrombi in mice noninvasively using single-photon emission computed tomography (SPECT). FibPep and a negative control peptide (NCFibPep) were synthesized and their fibrin-binding properties were assessed in vitro. FibPep showed enhanced binding compared with NCFibPep to both fibrin and blood clots. FibPep bound to fibrin with a dissociation constant (K(d)) of 0.8 μ m, whereas NCFibPep displayed at least a 100-fold lower affinity towards fibrin. A FeCl3 -injury carotid artery thrombosis mouse model was used to evaluate the peptides in vivo. FibPep and NCFibPep displayed rapid blood clearance and were eliminated via the renal pathway. In vivo SPECT imaging using FibPep allowed clear visualization of thrombi. Ex vivo biodistribution showed significantly increased uptake of FibPep in the thrombus-containing carotid in comparison to the noninjured carotid (5.7 ± 0.7 and 0.6 ± 0.4% injected dose per gram (%ID g(-1)), respectively; p < 0.01; n = 4), whereas nonspecific NCFibPep did not (0.4 ± 0.2 and 0.3 ± 0.0%ID g(-1), respectively; n = 4). In conclusion, FibPep displayed high affinity towards fibrin in vitro and rapid blood clearance in vivo, and allowed sensitive detection of thrombi using SPECT imaging. Therefore, this particular imaging approach may provide a new tool to diagnose and monitor diseases such as atherosclerosis and cancer.
authors.affiliation: Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: Lucas W E
authors.initials: LW
authors.lastname: Starmans
authors.forename: Sander M J
authors.initials: SM
authors.lastname: van Duijnhoven
authors.forename: Raffaella
authors.initials: R
authors.lastname: Rossin
authors.forename: Silvio
authors.initials: S
authors.lastname: Aime
authors.forename: Mat J A P
authors.initials: MJ
authors.lastname: Daemen
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
authors.forename: Holger
authors.initials: H
authors.lastname: Grüll
mesh_terms: D000818:Animals; D002341:Carotid Artery Thrombosis / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005337:Fibrin / Q000378:metabolism*; D007205:Indium Radioisotopes / Q000493:pharmacokinetics; D007553:Isotope Labeling / Q000379:methods; D008657:Metabolic Clearance Rate; D051379:Mice; D008810:Mice, Inbred C57BL; D057054:Molecular Imaging / Q000379:methods; D010455:Peptides / Q000737:chemistry / Q000493:pharmacokinetics*; D011485:Protein Binding; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D007205:Indium Radioisotopes; D010455:Peptides; D019275:Radiopharmaceuticals; D005337:Fibrin