X-ray imaging technique using colloid solution of Au/silica/poly(ethylene glycol) nanoparticles

This work describes X-ray imaging of mouse using colloid solution of silica coated Au (Au/SiO₂) nanoparticles surface modified with poly(ethylene glycol) (PEG) (Au/SiO₂/PEG). A colloid solution of Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate. Au/SiO₂ nanoparticles were fabricated by a sol-gel method using tetraethylorthosilicate, water and sodium hydroxide in ethanol in the presence of Au nanoparticles surface modified with (3-aminopropyl)- trimethoxysilane. A computed tomography value of the Au/SiO₂ colloid solution with an Au concentration of 0.083M was as high as 1421.2 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Surface modification of the Au/SiO₂ particles with PEG, or PEGylation of the particle surface, was performed using (3- aminopropyl)trimethoxysilane and PEG for the Au/SiO₂ particles. Tissues of mouse could be imaged by injecting the colloid solutions of Au/SiO₂ particles or Au/SiO₂/PEG particles into it. The PEGylation provided an increase in residence time of particles in the mouse.