title: Near-infrared fluorescent nanoparticles as combined MR/optical imaging probes.
abstract: A number of quantitative three-dimensional tomographic near-infrared fluorescence imaging techniques have recently been developed and combined with MR imaging to yield highly detailed anatomic and molecular information in living organisms (1, 2). Here we describe magnetic nanoparticle based MR contrast agents that have a near-infrared fluorescence (NIRF) that is activated by certain enzymes. The probes are prepared by conjugation of arginyl peptides to cross-linked iron oxide amine (amino-CLIO), either by a disulfide linkage or a thioether linker, followed by the attachment of the indocyanine dye Cy5.5. The NIRF of disulfide-linked conjugate was activated by DTT, while the NIRF of thioether-linked conjugate was activated by trypsin. Fluorescent quenching of the attached fluorochrome occurs in part due to the interaction with iron oxide, as evident by the activation of fluorescence with DTT when nanoparticles that have less than one dye attached per particle. With a SC injection of the probe, axillary and brachial lymph nodes were darkened on MR images and easily delineated by NIRF imaging. The probes may provide the basis for a new class of so-called smart nanoparticles, capable of pinpointing their position through their magnetic properties, while providing information on their environment by optical imaging techniques.
authors: Center for Molecular Imaging Research, Massachusetts General Hospital, Charlestown 02129, USA. josephso@helix.mgh.harvard.edu
authors: Lee
authors: L
authors: Josephson
authors: Moritz F
authors: MF
authors: Kircher
authors: Umar
authors: U
authors: Mahmood
authors: Yi
authors: Y
authors: Tang
authors: Ralph
authors: R
authors: Weissleder
mesh_terms: D000818:Animals; D001120:Arginine / Q000737:chemistry; D002232:Carbocyanines / Q000737:chemistry; D002478:Cells, Cultured; D003287:Contrast Media; D003432:Cross-Linking Reagents; D005290:Ferric Compounds / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008863:Microspheres; D015335:Molecular Probes; D010316:Particle Size; D010455:Peptides / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D013379:Substrate Specificity
chemical_list: C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D003287:Contrast Media; D003432:Cross-Linking Reagents; D005290:Ferric Compounds; D005456:Fluorescent Dyes; D015335:Molecular Probes; D010455:Peptides; C000499:ferric oxide; D001120:Arginine