Characterisation and evaluation of paramagnetic fluorine labelled glycol chitosan conjugates for (19)F and (1)H magnetic resonance imaging.

Medium molecular weight glycol chitosan conjugates have been prepared, linked by an amide bond to paramagnetic Gd(III), Ho(III) and Dy(III) macrocyclic complexes in which a trifluoromethyl reporter group is located 6.5 Å from the paramagnetic centre. The faster relaxation of the observed nucleus allows modified pulse sequences to be used with shorter acquisition times.

Paramagnetic 19F chemical shift probes that respond selectively to calcium or citrate levels and signal ester hydrolysis.

Paramagnetic magnetic resonance chemical shift probes containing a proximal CF(3) group have been characterised. Different systems have been created that report reversible changes in calcium ion concentrations in the millimolar regime, signal the presence of citrate selectively in competitive aqueous media and allow the monitoring of remote ester/amide hydrolysis in relayed, irreversible transformations. Chemical shift non-equivalence is amplified by the presence of the proximate lanthanide ion, with a mean separation between the CF(3) group and the metal ion of 6.

19F-lanthanide complexes with increased sensitivity for 19F-MRI: optimization of the MR acquisition.

Fluorine-19 magnetic resonance methods offer advantages for molecular or cellular imaging in vivo due to the absence of radioactivity, lack of naturally occurring background signal, and the ability to easily combine measurements with anatomical MRI. Previous studies have shown that (19) F-MRI sensitivity is limited to millimolar concentrations by slow longitudinal relaxation. In this study, a new class of macrocyclic fluorinated lanthanide complexes is investigated where relaxation rates are significantly shortened by proximity of the fluorine group to a paramagnetic lanthanide ion located within the same molecule.

Strategies to enhance signal intensity with paramagnetic fluorine-labelled lanthanide complexes as probes for 19F magnetic resonance.

The synthesis and (19)F NMR spectroscopic properties are reported for three series of CF(3)-labelled lanthanide(III) complexes, based on mono- and diamide cyclen ligands. Analyses of variable temperature, pH and field (19)F, (17)O and (1)H NMR spectroscopic experiments are reported and the merits of a triphosphinate mono-amide complex defined by virtue of its favourable isomer distribution and attractive relaxation properties. These lead to an enhanced sensitivity of detection in (19)F magnetic resonance experiments versus a diamagnetic Y(III) analogue, paving the way for future shift and imaging studies.

Design principles and theory of paramagnetic fluorine-labelled lanthanide complexes as probes for (19)F magnetic resonance: a proof-of-concept study.

The synthesis and spectroscopic properties of a series of CF(3)-labelled lanthanide(III) complexes (Ln=Gd, Tb, Dy, Ho, Er, Tm) with amide-substituted ligands based on 1,4,7,10-tetraazacyclododecane are described. The theoretical contributions of the (19)F magnetic relaxation processes in these systems are critically assessed and selected volumetric plots are presented. These plots allow an accurate estimation of the increase in the rates of longitudinal and transverse relaxation as a function of the distance between the Ln(III) ion and the fluorine nucleus, the applied magnetic field, and the re-rotational correlation time of the complex, for a given Ln(III) ion.