A luminescent and mesoporous core-shell structured Gd₂O ₃:Eu³⁺@nSiO₂@mSiO₂ nanocomposite as a drug carrier

In this paper, Gd₂O₃:Eu³⁺ nanospheres have been encapsulated with nonporous silica and further layer of ordered mesoporous silica through a simple sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption/desorption, photoluminescence (PL) spectra, and kinetic decay were used to characterize the sample. The results indicate that the nanocomposite with general 50 nm shell thickness and 270 nm core size shows typical ordered mesoporous characteristics (2.4 nm) and has spherical morphology with a smooth surface and narrow size distribution. Additionally, the obtained inorganic nanocomposite shows the characteristic emission of Eu³⁺ ( ⁵D₀ → ⁷F_1-4) even after the loading of drug molecules. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. Most importantly, the nanocomposite can be used as an effective drug delivery carrier. A typical anticancer drug, doxorubicin hydrochloride (DOX), was used for drug loading, and the DOX release, cytotoxicity, uptake behavior and therapeutic effects were examined. It was found that DOX is shuttled into the cell by the nanocomposite and released inside cells after endocytosis and that the DOX-loaded nanocomposite exhibited greater cytotoxicity than free DOX. These results indicate that core-shell structured Gd₂O₃:Eu ³⁺@nSiO₂@mSiO₂ nanocomposite has potential for drug loading and delivery into cancer cells to induce cell death.