Gold Nanoparticles as Contrast Agents in x-ray Imaging and Computed Tomography

Abstract

Computed tomography enables 3D anatomic imaging at a high spatial resolution, but requires delivery of an x-ray contrast agent to distinguish tissues with similar or low x-ray attenuation. Gold nanoparticles (AuNPs) have gained recent attention as an x-ray contrast agent due to exhibiting a high x-ray attenuation, nontoxicity and facile synthesis and surface functionalization for colloidal stability and targeted delivery. Potential diagnostic applications include blood pool imaging, passive targeting and active targeting, where actively targeted AuNPs could enable molecular imaging by computed tomography. This article summarizes the current state of knowledge for AuNP x-ray contrast agents within a paradigm of key structure-property-function relationships in order to provide guidance for the design of AuNP contrast agents to meet the necessary functional requirements in a particular application. Functional requirements include delivery to the site of interest (e.g., blood, tumors or microcalcifications), nontoxicity during delivery and clearance, targeting or localization at the site of interest and contrast enhancement for the site of interest compared with surrounding tissues. Design is achieved by strategically controlling structural characteristics (composition, mass concentration, size, shape and surface functionalization) for optimized properties and functional performance. Examples from the literature are used to highlight current design trade-offs that exist between the different functional requirements.

Renal Clearable Luminescent Gold Nanoparticles: From the Bench to the Clinic

“…Renal clearable AuNPs can serve as contrast agents for X‐ray imaging owing to the high X‐ray attenuation of gold atoms . The minimal dose for imaging the transport of GS‐AuNPs in the kidneys of mice is 1000 mg kg −1 , corresponding to 5.5×10 −3 mmol kg −1 (10–1000‐fold lower than the clinical doses of iodine agents for X‐ray imaging and CT, 0.05–5 mmol kg −1 ; Table S11).…”

Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies

“…There are probably more publications about gold nanoparticles than there are about all the rest of the elements combined. A recent review was entirely devoted to gold nanoparticles as contrast agents[182]. Although the high price of gold may make it impractical for use as a general-purpose intravascular contrast agent, there certainly may be specific applications for which the use of gold is potentially cost effective, for example as targeted contrast agents for oncology, or for theranostic contrast agents.…”

Macrophage with gold nanorod visualized by optical-resolution and acoustic-resolution photoacoustic microscopes

“…In these materials, gold reflects highest frequency and intensity of the PA signal and it would be suitable for PA signal enhancement in the cell. Gold is known to be nontoxic and it has been used for contrast agent for x-ray angiography [6]. However, gold is expensive material and the alternative material should be taken into account for clinical application.…”