Original Research Article
Year: 2019 | Month: July-September | Volume: 4 | Issue: 3 | Pages: 93-101
Synthesis and Evaluation of a Gd (III) Complex as T1-Weighted MRI Contrast Agent
Mahmuda Khannam
Research Scholar, Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
ABSTRACT
A hexadentate ligand, H4mum consisting of two phenyl moieties with four acetate arms was designed and synthesized. A water-soluble Gd(III) complex (1) was synthesized by reacting ligand H4mum with GdCl3·xH2O in 1:1 molar equivalent. Tb (III) congener (complex 2) of complex 1 was also synthesized and used for determining the number of coordinated water molecules present in the inner-coordination sphere of the complex by luminescence lifetime measurements. It was confirmed that the complex consisted of two directly coordinated-water molecules. At 25 °C and pH ~ 7.4 in HEPES buffer, the complex offered longitudinal relaxivity r1 value of 8.34 mM–1s–1 at a magnetic field of strength 1.41 T. However, with increasing filed strength to 14.1 T, the r1 relaxivity value slightly deceased to 7.62 mM–1s–1 at the same experimental conditions. The complex stability under physiological conditions was investigated by measuring r1 relaxivity in the presence of various physiological anions. In the presence of almost 100 equivalents (~ 50.0 mM) excess of these anions the r1 value remained almost constant, justified the complex stability under physiological conditions. Finally, phantom MR imaging under clinical scanner at 1.5 T showed positive contrast efficiency of the complex.
Keywords: MRI, Contrast agents, Gadolinium (III) complex, Relaxivity, Hydration state, High field.