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.
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Submitted on : Thursday, April 18, 2019 - 11:14:18 AM
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Geert Dehaen, Svetlana Eliseeva, Kristof Kimpe, Sophie Laurent, Luce Vander elst, et al.. A Self-Assembled Complex with a Titanium(IV) Catecholate Core as a Potential Bimodal Contrast Agent. Chemistry - A European Journal, Wiley-VCH Verlag, 2012, 18 (1), pp.293-302. ⟨10.1002/chem.201101413⟩. ⟨hal-02103245⟩

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