Core@shell nanoparticles with superparamagnetic iron oxide core, mesoporous silica shell, and crown ether periphery were fabricated toward drug delivery and tumor cell imaging. By the concept of nanovalve based on supramolecular gatekeeper, stimuli-responsive drug delivery nanosystems Fe3O4@SiO2@meso-SiO2@crown ethers were synthesized by (i) modified solvothermal reaction; (ii) sol-gel reaction; and (iii) amide coupling reaction. The successful coupling of the dibenzo-crown ethers onto the mesoporous silica shell was confirmed by thermogravimetric analysis and Infrared spectroscopy. In this system, the "ON/OFF" switching of the gatekeeper supramolecules can be controlled by pH-sensitive intramolecular hydrogen bonding or electrostatic interaction (such as metal chelating). Biological evaluation of the nanoparticles renders them noncytotoxic and can be uptaken by L929 cells. In this work, the antitumor drug (doxorubicin) loading and release profiles which were studied by the UV/visible absorption spectroscopy. The mechanism involves the best-fit binding of crown ethers with cesium or sodium ions at different pH values with ultrasonic wave in phosphate buffered saline (PBS). Magnetic resonance imaging analysis of the particles reveals a high relaxivity, rendering them potentially useful theranostic agents.

To increase the monodispersity of magnetic hybrid nanocomposites, a novel ultrasonic method was introduced to synthesize uniform Fe3O4@SiO2-Ag nanospheres. The immobilized Ag nanocrystals were tunable by varying the experimental conditions. An antibacterial assay indicated that the Fe3O4@SiO2-Ag nanospheres exhibited excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, in which the minimum inhibition concentrations (MIC) were 40 μg mL(-1) and 20 μg mL(-1), respectively. The live/dead bacterial cell fluorescence stain assay agreed well with the antibacterial assay. The CCK-8 results indicated these nanospheres were bio-compatible for human normal cells and presented relative cytotoxicity against HepG2 tumor cells. These nanospheres could be easily uptaken by the cells and they could affect bacterial cells both inside and outside the cell membrane, which enable them to be promisingly applied in future biomedical areas.

Novel high magnetization microspheres with porous γ-Fe(2)O(3) core and porous SiO(2) shell were synthesized using a templating method, whereas the size of the magnetic core and the thickness of the porous shell can be controlled by tuning the experimental parameters. By way of an example, as-prepared γ-Fe(2)O(3)@meso-SiO(2) microspheres (170 nm) display excellent water-dispersity and show photonic characteristics under externally applied a magnetic field. The magnetic property of the γ-Fe(2)O(3) porous core enables the microspheres to be used as a contrast agent in magnetic resonance imaging with a high r(2) (76.5 s(-1) mM(-1) Fe) relaxivity. The biocompatible composites possess a large BET surface area (222.3 m(2)/g), demonstrating that they can be used as a bifunctional agent for both MRI and drug carrier. Because of the high substrate loading of the magnetic, dual-porous materials, only a low dosage of the substrate will be acquired for potential practical applications. Hydrophobic zinc(II) phthalocyanine (ZnPC) photosensitizing molecules have been encapsulated into the dual-porous microspheres to form γ-Fe(2)O(3)@meso-SiO(2)-ZnPC microspheres. Biosafety, cellular uptake in HT29 cells, and in vitro MRI of these nanoparticles have been demonstrated. Photocytotoxicity (λ > 610 nm) of the HT29 cells uptaken with γ-Fe(2)O(3)@meso-SiO(2)-ZnPC microspheres has been demonstrated for 20 min illumination.