title: A new macromolecular paramagnetic MR contrast agent binds to activated human platelets.
abstract: A new functionalized macromolecular magnetic resonance (MR) contrast agent has been developed from a carboxymethyldextran-Gd(DOTA) devoid of biospecificity. The functionalized contrast agent was synthesized in order to mimic PSGL-1, the main ligand of P-selectin, a glycoprotein mainly expressed on the surface of activated platelets. The starting compound, CM1, was first carboxymethylated by monochloroacetic acid leading to a series of 10 derivatives varying in their carboxymethyl content. CM8 derivative, with a degree of substitution in carboxymethyl of 0.84, was chosen for subsequent fluorolabeling and sulfation to give CM8FS. CM8FS has an average number molecular weight of 27 000 +/- 500 g/mol, a hydrodynamic radius of 5.7 +/- 0.2 nm and a high relaxivity (r(1) = 11.2/mM (Gd)/s at 60 MHz). Flow cytometry experiments on whole human blood or on isolated platelets evidenced in vitro a preferential binding of CM8FS on TRAP-activated human platelets. Interestingly, CM8FS did not bind to other blood cells or to resting platelets. Pellets of TRAP-activated human platelets have also been imaged in tubes with a 1.5 T MR imager. A MR signal was observed for activated platelets incubated with CM8FS. Altogether, these in vitro results evidenced the recognition of activated human platelets by a fluorescent paramagnetic contrast agent grafted with carboxyl and sulfate groups. This biomimetic approach associated with the versatile macromolecular platform appears promising for the development of new contrast agents for molecular imaging of activated platelets in cardiovascular diseases such as atherosclerosis and aneurysms.
authors.affiliation: Inserm, U698, Cardiovascular Bio-engineering, CHU X. Bichat, University Paris 7, Paris, France. fchaubet@galilee.univ-paris13.fr
authors.forename: Frédéric
authors.initials: F
authors.lastname: Chaubet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bertholon
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Serfaty
authors.forename: Ramin
authors.initials: R
authors.lastname: Bazeli
authors.forename: Hasan
authors.initials: H
authors.lastname: Alsaid
authors.forename: Martine
authors.initials: M
authors.lastname: Jandrot-Perrus
authors.forename: Charaf
authors.initials: C
authors.lastname: Zahir
authors.forename: Pascale
authors.initials: P
authors.lastname: Even
authors.forename: Laure
authors.initials: L
authors.lastname: Bachelet
authors.forename: Ziad
authors.initials: Z
authors.lastname: Touat
authors.forename: Eric
authors.initials: E
authors.lastname: Lancelot
authors.forename: Claire
authors.initials: C
authors.lastname: Corot
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Canet-Soulas
authors.forename: Didier
authors.initials: D
authors.lastname: Letourneur
mesh_terms: D001792:Blood Platelets / Q000378:metabolism; D003287:Contrast Media / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins; D018716:Molecular Mimicry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000378:metabolism; D015539:Platelet Activation