Heavy element inorganic nanoparticles (NPs) have been proposed as long circulating X-ray contrast agents (XCAs) with the potential for site-directed imaging. Au and Bi are the most attractive elements to compose these NPs due to their high atomic numbers and anticipated biological compatibility. Synthetic preparations of Au NPs are well documented and surface modifications have been extensively explored. Relative to Au NPs, Bi NPs are more difficult to synthesize and functionalize; however, Bi NPs represent more attractive XCAs owing to the lower cost, greater abundance, and greater hydrolytic susceptibility of elemental Bi. The latter feature provides a means for biological clearance of the XCA. We have reported an aqueous and potentially biocompatible preparation of Bi NPs using long chain sugar polymers for colloidal and hydrolytic stability. However, the large hydrodynamic radius (HDR) to Bi nanocrystallite size indicates that the synthesis of these NPs can be improved to offer higher X-ray attenuation at lower NP concentrations by decreasing this ratio. To decrease the surfactant to Bi ratio, a synthetic strategy was developed utilizing sugar monomers to stabilize the Bi NPs. The use of the sugar monomer in place of the sugar polymer results in Bi NPs with a substantially smaller HDR. We examine the X-ray attenuation properties of these Bi NPs using both theoretical calculations and experimental phantom studies to determine Bi NP size and concentration necessary to achieve contrast in medical imaging.

Synthesis of aqueous sugar-coated bismuth nanoparticles

244th National Meeting (2012)

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