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The present study explores the synthesis and characterization of colloidal solutions comprising gold (Au) nanoparticles coated with bismuth oxide (Bi2O3), with the aim of developing potential X-ray contrast agents. The Au nanoparticles were synthesized by reducing Au (III) ions using tetrakis (hydroxymethyl) phosphonium chloride in an aqueous medium at 35 ℃, yielding nanoparticles with an average size of 2.2 ± 0.4 nm. Surface modification with polyvinylpyrrolidone (PVP) was employed to enhance the colloidal stability and facilitate the subsequent deposition of Bi2O3 shells. Bi2O3 coating was achieved via a controlled precipitation reaction between bismuth nitrate pentahydrate and sodium hydroxide in the presence of PVP-modified Au nanoparticles (Au/PVP). Transmission electron microscopy images confirmed the successful formation of Bi2O3 shells around the Au nanoparticles at various Au concentrations. The PVP-mediated stabilization effectively prevented nanoparticle aggregation, ensuring uniform Bi2O3 coating (Au/PVP/Bi2O3). Ultraviolet-visible extinction spectra and visual observations indicated that the Bi2O3 coating did not significantly alter the inherent properties of the Au/PVP nanoparticles. The resulting Au/PVP/Bi2O3 colloidal solution exhibited stability under the examined conditions, demonstrating its potential as an X-ray contrast agent with improved biocompatibility and imaging efficacy compared with conventional iodine-based agents. The combination of the high X-ray absorption and low toxicity of Au NPs with the inert characteristics and minimal toxicity of Bi2O3 presents a promising approach for developing advanced X-ray contrast agents with extended vascular retention and enhanced diagnostic capabilities.

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Effect of Polyvinylpyrrolidone Surface Modification on Properties of Bismuth-Oxide-Coated Gold Nanoparticles

  • 会议论文

  • 发表日期：

    2026年

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  • Soichiro Takiguchi,
  • Noriko Yamauchi,
  • Shohei Tada,
  • Takumu Takase,
  • Mone Kimura,
  • Kohsuke Gonda,
  • Yoshio Kobayashi

摘要

The present study explores the synthesis and characterization of colloidal solutions comprising gold (Au) nanoparticles coated with bismuth oxide (Bi2O3), with the aim of developing potential X-ray contrast agents. The Au nanoparticles were synthesized by reducing Au (III) ions using tetrakis (hydroxymethyl) phosphonium chloride in an aqueous medium at 35 ℃, yielding nanoparticles with an average size of 2.2 ± 0.4 nm. Surface modification with polyvinylpyrrolidone (PVP) was employed to enhance the colloidal stability and facilitate the subsequent deposition of Bi2O3 shells. Bi2O3 coating was achieved via a controlled precipitation reaction between bismuth nitrate pentahydrate and sodium hydroxide in the presence of PVP-modified Au nanoparticles (Au/PVP). Transmission electron microscopy images confirmed the successful formation of Bi2O3 shells around the Au nanoparticles at various Au concentrations. The PVP-mediated stabilization effectively prevented nanoparticle aggregation, ensuring uniform Bi2O3 coating (Au/PVP/Bi2O3). Ultraviolet-visible extinction spectra and visual observations indicated that the Bi2O3 coating did not significantly alter the inherent properties of the Au/PVP nanoparticles. The resulting Au/PVP/Bi2O3 colloidal solution exhibited stability under the examined conditions, demonstrating its potential as an X-ray contrast agent with improved biocompatibility and imaging efficacy compared with conventional iodine-based agents. The combination of the high X-ray absorption and low toxicity of Au NPs with the inert characteristics and minimal toxicity of Bi2O3 presents a promising approach for developing advanced X-ray contrast agents with extended vascular retention and enhanced diagnostic capabilities.