High relaxivity and stability of a hydroxyquinolinate-based tripodal monoaquagadolinium complex for use as a bimodal MRI/optical imaging agent.

An octadentate ligand based on triazacyclononane and 8-hydroxyquinolinate/phenolate binding units leads to very soluble, highly stable lanthanide complexes. The monoaquagadolinium complex shows a high relaxivity as a result of the unusually long rotational correlation time, fast water exchange rate, and slow electronic relaxation. The ligand also acts as sensitizer of the near-IR luminescence emission of the Yb and Nd ions. It appears as an excellent candidate for use as a bimodal imaging agent.

Synthesis and structure-activity relationships of C-glycosylated oxadiazoles as inhibitors of glycogen phosphorylase.

A series of per-O-benzoylated 5-beta-D-glucopyranosyl-2-substituted-1,3,4-oxadiazoles was prepared by acylation of the corresponding 5-(beta-D-glucopyranosyl)tetrazole. As an alternative, oxidation of 2,6-anhydro-aldose benzoylhydrazones by iodobenzene I,I-diacetate afforded the same oxadiazoles. 1,3-Dipolar cycloaddition of nitrile oxides to per-O-benzoylated beta-D-glucopyranosyl cyanide gave the corresponding 5-beta-D-glucopyranosyl-3-substituted-1,2,4-oxadiazoles. The O-benzoyl protecting groups were removed by base-catalyzed transesterification. The 1,3,4-oxadiazoles were practically inefficient as inhibitors of rabbit muscle glycogen phosphorylase b while the 1,2,4-oxadiazoles displayed inhibitory activities in the micromolar range. The best inhibitors were the 5-beta-D-glucopyranosyl-3-(4-methylphenyl- and -2-naphthyl)-1,2,4-oxadiazoles (K(i)=8.8 and 11.6 microM, respectively). A detailed analysis of the structure-activity relationships is presented.

Confinement of a tris-aqua Gd(iii) complex in silica nanoparticles leads to high stability and high relaxivity and supresses anion binding.

The water soluble tris-aqua complex [Gd(dhqN-SO3)(H2O)3](3-) based on a hexadentate hydroxyquinoline ligand shows high thermodynamic stability and high relaxivity (12.54 mM(-1) s(-1) at 1.2 T). Its non-covalent confinement in 25 nm silica nanoparticles prevents transmetallation and endogenous anion binding and leads to higher relaxivity over a wide range of magnetic fields.

Highly relaxing gadolinium based MRI contrast agents responsive to Mg2+ sensing.

A Gd complex based on a polyphosphonated pyridyl ligand shows a very high stability in aqueous solution (log K(EuL) = 25.7), a high relaxivity (8.5 mM(-1) s(-1) at 25 °C and 20 MHz) and a marked and selective relaxivity enhancement (37%) in the presence of Mg(2+), opening interesting perspectives for the design of cation responsive contrast agents.

Highly stable and soluble bis-aqua Gd, Nd, Yb complexes as potential bimodal MRI/NIR imaging agents.

A tripodal ligand based on the 8-hydroxyquinolinate binding unit yields a soluble and highly stable bis-hydrated Gd(3+) complex in water (pGd = 19.2(3)) with relaxivity change in the pH range 4.5-7.4 and Nd(3+), Yb(3+) analogues with sizeable NIR emission upon excitation at 370 nm providing a new architecture for the development of bimodal agents.

Lanthanide-chelate silica nanospheres as robust multicolor Vis-NIR tags.

Different lanthanide chelates have been simultaneously embedded in a silica matrix yielding bright dual-mode lanthanide doped nanospheres which are uniform in size distribution, tunable, photostable, and leakage free. Depending on the chelate combination, two color emission with a single light source or tunable emission with multiple sources is obtained.