Gold nanoparticles functionalized by gadolinium-DTPA conjugate of cysteine as a multimodal bioimaging agent.

The synthesis and characterization of gold nanoparticles coated with Gd-chelate (Au@GdL), where L is a conjugate of DTPA and cysteine, is described. These particles are obtained by the replacement of citrate from the gold nanoparticle surfaces with gadolinium chelate (GdL). The average size of Au@GdL is 14 nm with a loading of GdL reaching up to 2.9x10(3) per particles, and they demonstrate very high R1 relaxivity (approximately 10(5) mM(-1) s(-1)) as well as X-ray attenuation. The R1 relaxivity per [Gd] is 17.9 mM(-1) s(-1). The present system also exhibits macrophage-specific property, as demonstrated by histological and TEM images as well as CT and MR, rendering itself as a new class of T1 multimodal CT/MR contrast agent.