Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications
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This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol–gel process. The sol–gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2–NH2). Surface modification of the Au/SiO2–NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2–NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.
KeywordsAu Silica Core–shell Hydrogen storage Poly(ethylene glycol) X-ray contrast agent
We express our thanks to Prof. T. Noguchi at the College of Science of Ibaraki University, Japan for his support in TEM observations. This work was supported by a Grant-in-Aid for Scientific Research on Innovative Areas ‘‘Nanomedicine Molecular Science’’ (No. 2306) from Ministry of Education, Culture, Sports, Science, and Technology of Japan.
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