Fabrication of quantum dot/silica core-shell particles immobilizing Au nanoparticles and their dual imaging functions

The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core-shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core-shell particles with an average size of 47.0 +/- 6.1 nm was prepared by a sol-gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 +/- 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 +/- 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 degrees C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/ SiO2/Au particle colloid solution were 2.23 x 10(-7) (p/s/cm(2) /sr)/(lW/cm(2)) at a QD concentration of 8 x 10(-7) M and 1180 +/- 314 Hounsfield units and an Au concentration of 5.4 x 10(-2) M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes.