Synthesis of Colloidal Silver, Platinum, and Mixture of Silver-Platinum Nanoparticles Using Pulsed Laser Ablation as a Contrast Agent in Computed Tomography

The development of nanoparticles as computed tomography contrast agents has increased significantly. However, few reports have been published on the use of silver and platinum nanoparticles as contrast agents. These nanomaterials are a good candidatefor contrast agents because of their high atomic number and high durability against corrosion.
Experimentally, a Nd:YAG laser (1064 nm, 45 mJ, 10 Hz) was focused on a high-purity metal plate including Ag and Pt plates, which are placed in deionized water medium. Colloidal nanoparticles of Ag and Pt were then mixed to obtain a mixture composition of Ag and Pt with ratios of Ag:Pt of 75:25%, 50:50%, 25:75%, respectively.The Ag, Pt, and Ag-Pt NPs mixture were then examined as contrast agents in CT scan.
The imaging results of the quantitative analysiswere measured in the Hounsfield Unit(HU), showing 13.5, 12.8, 13.3, 14.1, and 17.3 HU for colloidal 100% AgNPs, colloidal Ag and Pt NPs with volume ratios of Ag:Pt of 75:25%, 50:50%, 25:75%, and colloidal 100%Pt NPs, respectively.
Results reveal the highest absorbent power was found in the colloidal contrast agent of Pt NPs 100% is 17.3 HU, followed by the 25:75% Ag-Pt NPs is 14.1 HU. The higher HU value for platinum can be attributed to its higher density since the effective energy of 80 kVp is about 42 keV, which is lower than the K-edge of Pt (K-edge ≈ 78 keV), which means that the attenuation of X-ray in Pt is due to Compton scattering dominantly.