Thiolated Gd(III) Chelate Coated Gold Nanoparticles: Synthesis, Characterization, X-Ray CT and MRI Relaxivity Studies

Abstract

Gadolinium complex of 2-aminothiophenol conjugated DTPA (DTPA=diethylenetriamine N,N,N',N",N" pentacetic acid) bis (amide) has been synthesized and characterized by various analytical techniques such as elemental analysis (EA), NMR, FAB-MS, IR, UV etc. This thiolated GdL (where L is a conjugate of DTPA and 2-aminothiophenol) has been anchored on the gold nanoparticles surfaces through thiols functionalites. These gold nanoparticles (AuNPs) have been synthesized by the reduction of gold tetrachloride (HAuCl 4 ) using sodium citrate as reducing agent. The surface functionalization has been performed by the replacement of citrate coat on the gold nanoparticle surface with thiolated Gd-chelate, Au@GdL. The Au@GdL has been analyzed by XRD, transmission electron microscope (HRTEM), UV, ICP-MS etc. The average size of nanoparticles is about 22 nm with a uniform spherical shape. A very high number of GdL has been loaded on nanoparticle surface reaching up to 7.9x10 3 of Gd (III)- chelates per nanoparticle and they demonstrate very high r 1 relaxivity and the r 1 relaxivity per [G is much higher than the Gd (III)-chelate alone. The bimodality has also been tested using in-vitro x- ray computed tomography (x- ray CT). These nanoparticles (GNPs) are very stable and homogeneously dispersed in aqueous solution.