Preparation of capsule-like particles containing single-core and their application to medical analysis

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Iodine compounds and gadolinium compounds have been used as contrast agents for X-ray CT and magnetic resonance imaging, respectively. These existing compounds may provoke adverse events as allergic reactions in patients, so that they can not be administered to such people. Core-shell nanoparticles are good candidates for prevention of allergic reactions because the shell materials can keep the contrast agents from living systems. In present works, several methods for silica-coating of contrast agent nanoparticles are proposed.Silica-coating of AgI nanoparticles with a Stober method was carried out to find out reaction conditions for control of the shell thickness. The AgI nanoparticles were prepared from AgCIO_4 and KI with the use of 3-mercaptopropyltrimethoxysilane (MPS) as a silane coupling agent and dimethylamine (DMA) catalyst for alkoxide hydrolysis. AgI-silica core-shell particles could be prepared with the use of 4.5×10^<-5> MMPS, 20M water, 0.01 MDMA and 1 mM AgI. Silica shell thickness could be varied from 15 to 28 nm with an increase in the TEOS concentration from 0.005 to 0.04M.A preparation method for multilayered silica-Gd-silica core-shell particles is proposes. Silica particles with an average size of 30.9 nm were prepared by the Stober method. Silica-Gd core-shell particles with a size of 57.4 nm were synthesized by a homogeneous precipitation method at 80℃ in water/propanol solution with 27.7 M H_2O, 0.001 M Gd (NO_3)_3, 0.5 M urea and 1 g/l polyvinylpyrrolidone in the presence of 0.001 vol% suspension of the silica particles. Succeeding silica-coating of the silica-Gd core-shell particles was performed with 0.0133 MTEOS and 0.002 M NaOH in the presence of a suspension of silica-Gd core-shell particles. Consequently, multilayered silica-Gd-silica core-shell particles with an average size of 71.2 nm could be obtained. These particles exhibited clear enhancement in magnetic resonance images.