X-ray computed tomography contrast agents prepared by seeded growth of gold nanoparticles in PEGylated dendrimer

Abstract

Gold nanoparticles (Au NPs) are a potential x-ray computed tomography (CT) contrast agent. A biocompatible and bioinactive surface is necessary for application of gold nanoparticle to CT imaging. Polyethylene glycol (PEG)-attached dendrimers have been used as a drug carrier with long blood circulation. In this study, the Au NPs were grown in the PEGylated dendrimer to produce a CT contrast agent. The Au NPs were grown by adding gold ions and ascorbic acid at various equivalents to the Au NP-encapsulated dendrimer solution. Both size and surface plasmon absorption of the grown Au NPs increased with adding a large number of gold ions. The x-ray attenuation of the Au NPs also increased after the seeded growth. The Au NPs grown in the PEG-attached dendrimer at the maximum under our conditions exhibited a similar CT value to a commercial iodine agent, iopamidol, in vitro. The Au NP-loaded PEGylated dendrimer and iopamidol were injected into mice and CT images were obtained at different times. The Au NP-loaded PEGylated dendrimer achieved a blood pool imaging, which was greater than a commercial iodine agent. Even though iopamidol was excreted rapidly, the PEGylated dendrimer loading the grown Au NP was accumulated in the liver.

Preparation of near-infrared light absorbing gold nanoparticles using polyethylene glycol-attached dendrimers

“…These results indicate that pH is very important in production of NIR-light absorbing Au NPs. The enhancement of the absorption in the formaldehyde-based seeding growth was much slower than that in the ascorbic acid-and sodium borohydride-based ones, as described in our previous reports [25,26]. These suggest that a slow reduction at low pH is necessary for preparation of the Au NP with NIR-absorption.…”

“…In our previous work, Au NPs were prepared by reducing Au(III) ions in PEGattached PAMAM dendrimers [24]. We also attempted seeding growth of Au NPs by reducing Au ions inside the dendrimer template under various conditions with different reductants, such as ascorbic acid and sodium borohydride [25,26]. Even though larger Au NPs could be obtained in these studies, the wavelength of the absorbing light remains to be improved for in vivo application.…”

Evaluation of the effects of gold nanoparticle shape and size on contrast enhancement in radiological imaging

“…Gold nanoparticles (AuNPs) are increasingly becoming the subject of investigation as radiographic contrast media (CM) [1][2][3][4][5]. The Au element is ideal for consideration as a radiopaque core in nanoparticulate contrast media due to its biocompatibility and relatively high attenuation coefficient values for X-rays in the diagnostic energy range [6][7][8][9].…”

Gold Nanoparticles as X-Ray, CT, and Multimodal Imaging Contrast Agents: Formulation, Targeting, and Methodology

“…Mice were injected with formulated particles or iopamidol in a comparison of contrasting ability and halflife. HU values were similar for both CA, although iopamidol accumulated within the bladder due to renal elimination [87].…”