title: Use of paramagnetic chelated metal derivatives of polysaccharides and spin-labeled polysaccharides as contrast agents in magnetic resonance imaging.
abstract: Soluble and insoluble polysaccharides were derivatized with diethylenetriaminepentaacetic acid (DTPA) and/or spin-labeled with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Polysaccharides derivatized with DTPA were prepared via cyanogen bromide activation, coupling to a diamine linker, and to DTPA anhydride. Spin-labeled polysaccharides were also prepared via cyanogen bromide activation. The extent of derivatization for dextran (18 kDa) was about 120 glucose units per DTPA, and for cellulose and starch about 15-30 units per DTPA. For spin-labeled polysaccharides, the average loading ranged from 1 nitroxide per 16 glucose units for starch to 181 for dextran (82 kDa). These derivatized paramagnetic polysaccharides were shown to be more effective relaxants than the small paramagnetic molecules alone. Both soluble and insoluble polysaccharide-linker-DTPA-Gd(III) complexes were effectively cleared from the body (rats) after oral administration. After intravenous administration, the biodistribution of dextran-linker-DTPA-Gd(III) complexes differed significantly from that of GdDTPA. Reduction of the nitroxide by ascorbic acid was retarded in the polysaccharide derivatives, particularly in starch derivatized with both nitroxide and linker-DTPA-Cu(II). These agents showed contrast enhancement in the gastrointestinal tract of rabbits.
authors.affiliation: Department of Chemistry, Birkbeck College, London, United Kingdom.
authors.forename: S W
authors.initials: SW
authors.lastname: Bligh
authors.forename: C T
authors.initials: CT
authors.lastname: Harding
authors.forename: P J
authors.initials: PJ
authors.lastname: Sadler
authors.forename: R A
authors.initials: RA
authors.lastname: Bulman
authors.forename: G M
authors.initials: GM
authors.lastname: Bydder
authors.forename: J M
authors.initials: JM
authors.lastname: Pennock
authors.forename: J D
authors.initials: JD
authors.lastname: Kelly
authors.forename: I A
authors.initials: IA
authors.lastname: Latham
authors.forename: J A
authors.initials: JA
authors.lastname: Marriott
mesh_terms: D000818:Animals; D002482:Cellulose; D002614:Chelating Agents / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry; D003911:Dextrans; D003959:Diamines / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008670:Metals / Q000737:chemistry; D009589:Nitrogen Oxides / Q000737:chemistry; D004369:Pentetic Acid / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D011817:Rabbits; D013113:Spin Labels; D013213:Starch
chemical_list: D002614:Chelating Agents; D003287:Contrast Media; D003497:Cyclic N-Oxides; D003911:Dextrans; D003959:Diamines; D005609:Free Radicals; D008670:Metals; D009589:Nitrogen Oxides; D011134:Polysaccharides; D013113:Spin Labels; D004369:Pentetic Acid; D002482:Cellulose; D013213:Starch; C039900:nitroxyl; C003959:TEMPO