Yu Shen Lin

Multifunctional mesoporous silica nanoparticles for intracellular labeling and animal magnetic resonance imaging studies

The unique properties of mesoporous silica nanoparticles (MSNs), such as high surface areas, uniform pore size, easy modification, and biocompatibility, make them highly suitable for biological applications. In previous reports, MSNs have been demonstrated to function as cell markers and as gene transfection and drug delivery agents. Although these cell-level studies are attractive, some important issues, such as the cellular uptake efficiency, toxicity, and circulation behavior of MSNs in living animals, still have to be addressed for further practical animal-level applications. Superparamagnetic nanoparticles (i.e. , magnetite) with diameters of less than 20 nm exhibit effective magnetic resonance imaging (MRI) contrast enhancement behavior. Because MRI is a noninvasive imaging method, it is a powerful tool with which to track the migration of cells and to investigate the distribution of nanoparticles in the living body. The main drawbacks of the MRI technique, however, are low sensitivity and resolution, which make it unable to provide detailed biological information. In previous reports, magnetic–optical bifunctional nanoparticles have been fabricated for imaging applications. However, they are nonporous hybrid magnetic composites. To offset the shortcomings and to expand the bioimaging/delivery ACHTUNGTRENNUNGapplications, simultaneous attachment of a fluorescent probe (subcellular imaging) and a MRI probe (noninvasive imaging) to MSN is an important task. Recently, we adopted a strategy involving the simultaneous fusion of amorphous silica shells of Fe3O4@SiO2 nanoparticles with MSNs that are attached to fluorescein isothiocyanate (FITC). These nanoparticles with multifunctionalities—fluorescent, magnetic, and porous (MagDye@MSNs)—can simultaneously serve as bimodal imaging probes and drug reservoirs. Thus, we believe that MagDye@MSNs would be a suitable material with which to study the cellular uptake efficiency, toxicity, and accumulative behavior of MSNs in living animals. To the best of our knowledge, this is the first report of direct injection of mesoporous silica nanoparticles (MSNs) into mice and of in vivo visualization of the localization of MSNs by MRI. Mag-Dye@MSNs were synthesized according to the method we previously developed (the detailed synthetic method is described in the Experimental Section). A transmission electron microscopy (TEM) image of the Mag-Dye@MSNs (Figure 1)

Catalytic nano-rattle of Au@hollow silica: towards a poison-resistant nanocatalyst

In this work, size-controlled gold nanocatalysts (2.8 to 4.5 nm) inside monodisperse hollow silica nanospheres, Au@HSNs, have been prepared by using a water-in-oil microemulsion as a template. The size of gold nanocatalysts can be easily controlled based on the gold precursor and the chloroauric acid concentration used during synthesis. These Au@HSN nanocatalysts were characterized by transmission electron microscopy, scanning electron microscopy, N2 adsorption–desorption isotherms, powder X-ray diffraction, and UV-vis spectrometer. Furthermore, we demonstrate their catalytic capability with respect to the 4-nitrophenol reduction reaction in the absence and presence of a thiol compound, meso-2,3-dimercaptosuccinic acid. The results show that the Au@HSNs display highly catalytic activity and resistance to other strongly adsorbing molecules in reaction solutions.

Synthesis of hollow silica nanospheres with a microemulsion as the template

We demonstrate a sol-gel approach, using a water-in-oil microemulsion as the template, for the synthesis of hollow and yolk/shell silica nanospheres, which can encapsulate pre-formed hydrophobic nanoparticles, and we then explore these multifunctional hollow nanospheres in cell-labeling applications.

Mesoporous Silica Nanoparticles Improve Magnetic Labeling Efficiency in Human Stem Cells

Tumblerlike magnetic/fluorescein isothiocyanate (FITC)-labeled mesoporous silica nanoparticles, Mag-Dye@MSNs, have been developed, which are composed of silica-coated core-shell superparamagnetic iron oxide (SPIO@SiO(2)) nanoparticles co-condensed with FITC-incorporated mesoporous silica. Mag-Dye@MSNs can label human mesenchymal stem cells (hMSCs) through endocytosis efficiently for magnetic resonance imaging (MRI) in vitro and in vivo, as manifested by using a clinical 1.5-T MRI system with requirements of simultaneous low incubation dosage of iron, low detection cell numbers, and short incubation time. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes, which can still be readily detected by MRI. Moreover, a higher MRI signal intensity decrease is observed in Mag-Dye@MSN-treated cells than in SPIO@SiO(2)-treated cells. This is the first report that MCM-41-type MSNs are advantageous to cellular uptake, as manifested by a higher labeling efficiency of Mag-Dye@MSNs than SPIO@SiO(2).

High payload Gd(III) encapsulated in hollow silica nanospheres for high resolution magnetic resonance imaging

For clear MR imaging of blood vessels, a long blood circulation time of effective T1 contrast agents is necessary. Nanoparticulate MR contrast agents are much more effective owing to their enhanced relaxivity, a result of reduced tumbling rates, and large payloads of active magnetic species. PEGylated yolk-shell silica nanospheres containing high payloads of Gd(iii) with cross-linking ligands are synthesized and evaluated as a blood-pool magnetic resonance contrast agent. The hydrophilic PEG coating and the microporous silica shell allow water exchange while keeping the multi-nuclear Gd species from leaching out. These Gd(iii)-containing yolk-shell silica nanoparticles with PEGylated surfaces give excellent resolution and contrast in magnetic resonance angiography images of vasculature in rat brains.

Laser action in Tb(OH) 3 /SiO 2 photonic crystals

Photonic crystals of Tb(OH)(3)/SiO(2) core/shell nanospheres with different periodicities were used as a resonant cavity to explore laser action. By changing the particle size, the optical stop band of the photonic crystals can be tuned to coincide with the multiple emission bands of terbium ions. An overlap of the stop band on the multiple emissions of the active materials embedded inside the photonic crystals offered a good chance for resonance. Lasing emissions arising from terbium ions occurred near the band edge of the PCs were demonstrated.

Multifunctional mesoporous silica nanoparticles as dual-mode imaging probes

Abstract We develop a strategy for the synthesis of multifunctional nanoparticles of mesoporous silica (Mag-Dye@MSN) that simultaneously possesses magnetic, luminescent, and mesoporous properties. These nanoparticles exhibit high T2 relaxivity and visible light emission. We further explore the potential of utilizing these multiple functionalities as dual-imaging probes for the labeling of biological cells and evaluate the cytotoxicity of Mag-Dye@MSN. These preliminary results demonstrate the potential of using these multifunctional nanoparticles for cell-labeling and integrated diagnosis applications.

Integrated nanophotonic hubs based on ZnO-Tb(OH)3/SiO2 nanocomposites

Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH)3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH)3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH)3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH)3/SiO2 as well as SnO2-Tb(OH)3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.