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 (HAuCl4) 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 7.9x103 of Gd (III)- chelates per nanoparticle and they demonstrate very high r1 relaxivity and the r1 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.