title: A self-assembled complex with a titanium(IV) catecholate core as a potential bimodal contrast agent.
abstract: A ditopic chelating ligand (H(6)4) that bears catechol and diethylenetriamine-N,N,N',N'',N''-pentaacetate (DTPA) has been designed and shown to specifically bind lanthanide(III) ions at the DTPA core ([Ln(H(2)4)(H(2)O)](-)) and further self-assemble with titanium(IV), thereby giving rise to the formation of a supramolecular metallostar complex with a lanthanide(III)-to-titanium(IV) ratio of 3:1, [(Ln4)(3)Ti(H(2)O)(3)](5-) (Ln=La, Eu, Gd). The efficacy of the metallostar complex as a potential bimodal optical/magnetic resonance imaging (MRI) agent has been evaluated. Nuclear magnetic relaxation dispersion (NMRD) measurements for the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex have demonstrated an enhanced r(1) relaxivity that corresponds to 36.9 s(-1) mM(-1) per metallostar molecule at 20 MHz and 310 K, which is a result of a decreased tumbling rate. The ability of the complex to bind to human serum albumin (HSA) was also examined by relaxometric measurements. In addition, upon UV irradiation the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex exhibits broad-band green emission in the range 400-750 nm with a maximum at 490 nm. Taking into account the high relaxivity and luminescence properties, the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex is a good lead compound for the development of efficient bimodal contrast agents.
authors.affiliation: Katholieke Universiteit Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, 3001 Heverlee, Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: Dehaen
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Eliseeva
authors.forename: Kristof
authors.initials: K
authors.lastname: Kimpe
authors.forename: Sophie
authors.initials: S
authors.lastname: Laurent
authors.forename: Luce
authors.initials: L
authors.lastname: Vander Elst
authors.forename: Robert N
authors.initials: RN
authors.lastname: Muller
authors.forename: Wim
authors.initials: W
authors.lastname: Dehaen
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans
authors.forename: Tatjana N
authors.initials: TN
authors.lastname: Parac-Vogt
mesh_terms: D002396:Catechols / Q000138:chemical synthesis* / Q000737:chemistry; D003287:Contrast Media / Q000138:chemical synthesis* / Q000737:chemistry; D005682:Gadolinium / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D004369:Pentetic Acid / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D002396:Catechols; D003287:Contrast Media; D028581:Lanthanoid Series Elements; D009942:Organometallic Compounds; D004369:Pentetic Acid; D005682:Gadolinium; D014025:Titanium