Up-conversion nanoparticle assembled mesoporous silica composites: synthesis, plasmon-enhanced luminescence, and near-infrared light triggered drug release.

A facile process for the preparation of multifunctional nanospheres combining several advantages of mesoporous channels, up-conversion (UC) luminescence, and photothermal responses into one single entity is reported. First, Gd2O3:Yb/Er assembled mesoporous silica with 2D hexagonal (MCM-41) and 3D cubic (MCM-48) network have been prepared via a one-step procedure. Then, gold nanocrystals with diameter of 5 nm are integrated with the amino group functionalized nanocomposites. Upon 980 nm near infrared (NIR) laser irradiation, a wavelength-dependent enhancement of the UC intensities is observed due to the surface plasmon resonance (SPR) effect of attached gold nanoparticles. These composites have good biocompatibility and sustained anticancer drug (doxorubicin, DOX) release properties, making it a promising candidate for drug delivery. Particularly, under 980 nm NIR laser irradiation, the green UC emission overlaps the SPR band of gold nanocrystals, which causes a photothermal effect of gold nanocrystals and induces a rapid DOX release from the Au hybrid materials. This DOX loaded multifunctional system has an obvious cytotoxic effect and photothermally killing enhanced effect on SKOV3 ovarian cancer cells. The endocytosis process was also demonstrated through confocal laser scanning microscope (CLSM) images. Such novel multifunctional anticancer drug delivery systems, which combine hyperthermia with the chemotherapeutic drugs by synergistic effect, should be of high potential in cancer therapy.