Core–shell monodisperse spherical mSiO2/Gd2O3:Eu3+@mSiO2 particles as potential multifunctional theranostic agents

Core–shell nanoparticles with diameters in the range 100–500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5–100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g−1) and pore volume (0.3 cm3 g−1), and are bright solid phosphor with superior stability in aqueous media. The core–shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.