Spin Labeled Chelating Agents and their Gadolinium Complexes as Contrast Enhancing Agents for NMR Imaging

Abstract

<jats:p>Spin labeled EDTA, CDTA and DTPA chelating agents and their gadolinium complexes were synthesized and evaluated for their effects on the spin-lattice (T<jats:sub>1</jats:sub>) and spin-spin (T<jats:sub>2</jats:sub>) relaxation times of water, plasma, and blood. It was found that the spin labeled chelating agents are effective proton relaxation agents. Although, the gadolinium complexes of these agents have superior relaxation properties, the differences in relaxivitv between the spin labeled complexes and the non-spin labeled gadolinium complexes are marginal. The spin labeled agents and their gadolinium complexes are expected to be very useful in designing paramagnetic conjugates with biomolecules. In particular, the latter type possesses high proton relaxivity combined with a nitroxvl marker which can be followed pharmacokinetically by EPR. </jats:p>

Synthesis of Water Soluble Spin Labeled Glucose Derivatives as Potential NMR Contrast Enhancing Agents

“…The T, and T2 values for plasma were found to be shorter than those obtained for w ater (Table I). This result is, in part, contrary to results obtained in our laboratory with various nitroxyl derivatives other than carbohydrates [30,31] A lthough the new relaxation enhancers are all w ater soluble, it is, nevertheless, expected that be cause of two different nitroxyls used and because of various bridge elements between the nitroxyl and carbohydrate moieties, the new compounds will pos sess a range of partitioning properties which will make some of them more suitable for diffusion through m em branes such as BBB. This topic is now actively pursued in our laboratories.…”

Fundamental Coordination Chemistry, Environmental Chemistry, and Biochemistry of Lead(II)

“…Amido functional groups were selected because of earlier reports by Battistizzi et al (215) that this functionality confers selective binding for Pb(II) over other metal ions and because related amido-functionalized ligands have been successfully employed in coordination compounds used for magnetic resonance imaging spectroscopy (216)(217)(218). Out of the series of complexes that were prepared, the most soluble was the tetraamido analogue, Pb II -EDTA-N 4 , which exhibits a discrete 1:1 ligand/metal complex in the solid state.…”

A numerical prediction of spin-lattice relaxation enhancement of water protons by paramagnetic metal ions and free radicals. A contribution to the basic principles of relaxometry in MRI

“…(16) and (20). The terms •oh and fe) s are spectral density functions which are further delineated into a very complex expression [41].…”

“…(13)-- (16), and (18)- (22), which have been based on translational diffusion models can be "normalized" to give the general expression Eq. (24), where mis the molarity, F is the methodical factor, and 1.067 is the numerical factor encompassing all constants which will remain the same as long as specifically the relaxation of water protons is involved.…”

“…In order to normalize the Eqs. (14) and (15) a D~s (16) where Cs is the concentration of spins per tmit volume, Dls is the mutual translational self diffusion coefficient of molecules containing I and S spins, anda is the distance of the closest approach of I and S. Replacement of Dis coefficient with the Stokes-Einstein formula [33,38,39]: …”