2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Biomolecule Stabilized Palladium Nanoparticles as X-ray Contrast Agents for CT Imaging

S.K. Nune, A. Tinsley, E.J. Boote, K.V. Katti and R. Kannan
University of Missouri-columbia, US

CT imaging, palladium, nanoparticles, nontoxic, biomolecule, simulation, phantom

Metallic nanoparticles have attracted significant attention in the design and development of new X-ray contrast agents for CT imaging.1 The high atomic number of palladium has prompted us toward investigation into the application of these nanoparticles as contrast enhancers in X-ray imaging. However periodic properties suggest that palladium has some advantages over gold as a contrast enhancer with an X-ray beam with a lower mean energy. This is because the lower energy of the k-edge absorption peak is situated closer to the mean energy of the spectrum of X-rays. For palladium, this k-edge is at 24.35 keV. Our study encompasses the following: (i) the synthesis of biomolecule-PdNP conjugate using non-toxic reducing agent, (ii) simulation studies on change in CT number (HU) using PdNP’s at 80 kVp. (iii) Phantom CT studies using biomolecule stabilized PdNP’s. Synthesis of nontoxic biomolecule-PdNP conjugate: The palladium nanoparticles were synthesized by mixing aqueous solutions of nontoxic reducing agent (trishydroxyphosphine alanine, ‘Katti’s Peptide’, THPAL)2,3 to the aqueous solution of carbohydrate or biomolecule containing Na2PdCl4 solution at elevated temperature (95-100 oC). Upon addition, the color of the reaction changes from pale yellow to light dark brown indicating the formation of palladium nanoparticles. Simulation Studies: We performed the CT simulation studies by varying the concentration of palladium (1.25 mg/mL-3.0 mg/mL). Our studies clearly revealed that change in CT number is consistent with and tracks with concentration. We also observed that change in CT number (HU) with concentration is higher in palladium compared to gold (Figure 2b). CT-Phantom Studies: Non toxic phytochemicals, Gum Arabic and Gelatin were used as biomolecules to stabilize Palladium nanoparticles. A Gammex/RMI Model 461 phantom was scanned using a Siemens volume zoom CT system. Two 20 mL glass vials containing aqueous solutions of various concentrations of PdNPs were placed in holders in the phantom. This arrangement presented a tissue like (solid water) background with PdNP’s contrast inclusions. Simulation studies coupled with the preliminary phantom CT imaging studies clearly demonstrate that change in CT number is consistent with and tracks with concentrations. Further investigations on the change in CT number in gold and other metallic nanoparticles are underway.

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