New bifunctional H(4)dota-like ligands with three acetic acid and one phosphinic acid pendant arms and propionate (H(5)do3ap(PrA)) or 4-aminobenzyl (H(4)do3ap(ABn)) reactive groups bound to the phosphorus atom were investigated. Potentiometric studies showed that the ligands have a similar basicity to the parent H(4)dota and the stability constants of their complexes with sodium(i) and selected lanthanide(III) ions are also similar. Formation and acid-assisted decomplexation kinetics of yttrium(III) complexes with a series of H(4)dota-like ligands (H(4)dota and its phosphinic/phosphonic acid analogues) were studied and the reactions are sensitive to a slight modification of the ligand structure. The (2-carboxyethyl)phosphinic acid derivative H(5)do3ap(PrA) and the phosphonic acid ligand H(5)do3ap form complexes faster than H(4)dota. The most kinetically inert complex is that with H(4)do3ap(ABn). Rates of complexation and decomplexation can depend on the ability to transfer proton(s) outside/inside the complex cavity and, therefore, on the hydrophobicity of the ligands. The results demonstrate that the new bifunctional ligands are suitable for labelling biomolecules with yttrium(iii) radioisotopes for utilization in nuclear medicine.

ABSTRACT:The preparation and characterization of a novel polymeric drug-delivery system designed for bone targeting of antineoplastics is described. The system was based on biocompatible poly[N-(2-hydroxypropyl)methacrylamide] carrier containing hydroxybisphosphonate targeting moieties and the model radiotherapeutics 125 I or 111 In or the anticancer drug doxorubicin. The in vitro binding studies with hydroxyapatite as a bone model proved that the system was efficiently adsorbed on this mineral. The systems contained model drugs bound by stable (amide), hydrolytically cleavable (hydrazone) or enzymatically cleavable (Gly-PheLeu-Gly tetrapeptide) spacers. It was proven in vitro that, in the case of cleavable spacers, the drug could be released from the polymer carrier at a rate depending on the pH or enzymatic stimulus.

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The luminescence lifetimes of europium(III) complexes with new monophosphorus acid derivatives of H(4)dota were measured by means of time-resolved laser-induced luminescence spectroscopy in H(2)O and D(2)O. The hydration numbers of these complexes were estimated using different empirical equations [Horrocks and Sudnick (1979) J. Am. Chem. Soc. 101 (1979) 334; Choppin and Barthelemy(1989) Inorg. Chem. 28, 3354-3357; Choppin and Bünzli Lanthanide probes in life, chemical and earth sciences. Theory and practice (1989); Kimura and Kato J. Alloys Comp. 275-277 (1998) 806; Parker (1999) J. Chem. Soc., Perkin Trans. 2, 493-503; Supkowski and Horroks (2002) Inorg. Chim. Acta. 340, 44-48]. It was shown that all the relationships gave similar results with a satisfactory precision. The hydration numbers of complexes of H(3)do3a and H(4)dota agreed with the literature values. One water molecule is coordinated in complexes of the new ligands. The results showed that the Choppin formula based on measurements only in H(2)O can be satisfactorily used for estimation of the hydration numbers.

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