title: Annexin V-CLIO: a nanoparticle for detecting apoptosis by MRI.
abstract: Annexin V, which recognizes the phosphatidylserine of apoptotic cells, was conjugated to crosslinked iron oxide (CLIO) nanoparticles, a functionalized superparamagnetic preparation developed for target-specific magnetic resonance imaging (MRI). The resulting nanoparticle had an average of 2.7 annexin V proteins linked per CLIO nanoparticle through disulfide bonds. Using camptothecin to induce apoptosis, a mixture of Jurkat T cells (69% healthy and 31% apoptotic) was incubated with annexin V-CLIO and was applied to magnetic columns. The result was an almost complete removal of the apoptotic cells (> 99%). In a phantom MRI experiment, untreated control cells (12% apoptotic cells, 88% healthy cells) and camptothecin-treated cells (65% apoptotic cells, 35% healthy cells) were incubated with either annexin V-CLIO (1.0, 0.5, and 0.1 microgram Fe/mL) or with unlabeled CLIO. A significant signal decrease of camptothecin-treated cells relative to untreated cells was observed even at the lowest concentration tested. Unmodified CLIO failed to cause a significant signal change of apoptotic cells. Hence, annexin V-CLIO allowed the identification of cell suspensions containing apoptotic cells by MRI even at very low concentrations of magnetic substrate. Conjugation of annexin V to CLIO affords a strategy for the development of a MRI imaging probe for detecting apoptosis.
authors.affiliation: Massachusetts General Hospital, Charlestown, MA, USA.
authors.forename: Eyk A
authors.initials: EA
authors.lastname: Schellenberger
authors.forename: Alexei
authors.initials: A
authors.lastname: Bogdanov
authors.forename: Dagmar
authors.initials: D
authors.lastname: Högemann
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tait
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
authors.forename: Lee
authors.initials: L
authors.lastname: Josephson
mesh_terms: D017304:Annexin A5 / Q000493:pharmacokinetics*; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000633:toxicity; D002470:Cell Survival; D003432:Cross-Linking Reagents; D005290:Ferric Compounds / Q000493:pharmacokinetics; D006801:Humans; D019169:Jurkat Cells; D016399:Lymphoma, T-Cell; D008279:Magnetic Resonance Imaging / Q000379:methods*
chemical_list: D017304:Annexin A5; D003432:Cross-Linking Reagents; D005290:Ferric Compounds; C000499:ferric oxide; D002166:Camptothecin