Gold nanoparticles coated with gadolinium-DTPA-bisamide conjugate of penicillamine (Au@GdL) as a T1-weighted blood pool contrast agent

The work is directed toward the synthesis and characterization of gold nanoparticles coated by Gd-chelate (Au@GdL), where L is a conjugate of diethylenetriamine-N, N, N′, N′′, N′′-pentaacetic acid (DTPA) and penicillamine. Au@GdL is obtained by the replacement of citrate from Au@citrate with gadolinium chelate (GdL). The average size of Au@GdL is 12 nm with the loading of GdL reaching up to 3.0 × 10³ per particle, and they exhibit very high r₁ relaxivity (∼10⁷ mM^-1 s^-1) as well as X-ray attenuation. The r₁ relaxivity per [Gd] is 20.1 mM^-1 s^-1. The small size of the present system also exhibits a USPIO-like behavior, such as contrast enhancement in the liver, the blood pool and the lymph node, 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 with potential application to the blood pool and the lymph node.