Yann Hung

Size Effect on Cell Uptake in Well‐Suspended, Uniform Mesoporous Silica Nanoparticles

because itdetermines the mechanism and rate of cell uptake of ananoparticle and its ability to permeate through tissue. Theinvestigation of particle size effects will impact on allapplications of nanoparticles in biomedicine. It has beenfoundthatparticlesizecanaffecttheefficiencyandpathwayofcellularuptakebyinfluencingtheadhesionoftheparticlesandtheir interaction with cells.

Highly efficient cellular labeling of mesoporous nanoparticles in human mesenchymal stem cells: implication for stem cell tracking

Tracking the distribution of stem cells is crucial to their therapeutic use. However, the usage of current vectors in cellular labeling is restricted by their low internalizing efficiency. Here, we reported a cellular labeling approach with a novel vector composed of mesoporous silica nanoparticles (MSNs) conjugated with fluorescein isothiocyanate in human bone marrow mesenchymal stem cells and 3T3‐L1 cells, and the mechanism about fluorescein isothiocyanate‐conjugated MSNs (FITC‐MSNs) internalization was studied. FITC‐MSNs were efficiently internalized into mesenchymal stem cells and 3T3‐L1 cells even in short‐term incubation. The process displayed a time‐ and concentration‐dependent manner and was dependent on clathrin‐mediated endocytosis. In addition, clathrin‐dependent endocytosis seemed to play a decisive role on more internalization and longer stay of FITC‐MSNs in mesenchymal stem cells than in 3T3‐L1 cells. The internalization of FITC‐MSNs did not affect the cell viability, proliferation, immunophenotype, and differentiation potential of mesenchymal stem cells, and 3T3‐L1 cells. Finally, FITC‐MSNs could escape from endolysosomal vesicles and were retained the architectonic integrity after internalization. We conclude that the advantages of biocompatibility, durability, and higher efficiency in internalization suit MSNs to be a better vector for stem cell tracking than others currently used.

Mesoporous silica nanoparticles as nanocarriers

Modern nanomedicine aims at delivering drugs or cells specifically to defective cells; therefore, this calls for developing multifunctional nanocarriers for drug delivery and cell-tracking. Mesoporous silica nanoparticles (MSNs) are well suited for this task. In this feature article, we highlight the strategies in the synthesis and functionalization of small, uniform and colloidal stable MSNs. We then discuss cell uptake of MSNs and tracking cells, as both aspects are closely related to the efficacy of drug delivery and theranostics. Some examples of stimulated drug delivery are described. For application considerations, toxicity and pharmacokinetics are critical issues and in vivo studies are summarized.

Mesoporous Silica Nanoparticles as a Delivery System of Gadolinium for Effective Human Stem Cell Tracking

The progress of using gadolinium (Gd)-based nanoparticles in cellular tracking lags behind that of superparamagnetic iron oxide (SPIO) nanoparticles in magnetic resonance imaging (MRI). Here, dual functional Gd-fluorescein isothiocyanate mesoporous silica nanoparticles (Gd-Dye@MSN) that possess green fluorescence and paramagnetism are developed in order to evaluate their potential as effective T1-enhancing trackers for human mesenchymal stem cells (hMSCs). hMSCs are labeled efficiently with Gd-Dye@MSN via endocytosis. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes, osteocytes, and chondrocytes, which can still be readily MRI detected. Imaging, with a clinical 1.5-T MRI system and a low incubation dosage of Gd, low detection cell numbers, and short incubation times is demonstrated on both loaded cells and hMSC-injected mouse brains. This study shows that the advantages of biocompatibility, durability, high internalizing efficiency, and pore architecture make MSNs an ideal vector of T1-agent for stem-cell tracking with MRI.

Monoclonal antibody-functionalized mesoporous silica nanoparticles (MSN) for selective targeting breast cancer cells

In this work, we conjugate anti-HER2/neu mAb (monoclonal antibody) to green fluorescent dye loaded mesoporous silica nanoparticles (Her-Dye@MSN) through a polyethylene glycol (MW = 5000) spacer. We examine their targeting properties toward HER2/neu over-expressing breast cancer cells and their internalization into the cells. Her-Dye@MSN nanoparticles exhibit a high targeting efficiency and the specific targeting capability is strongly affected by the mAb density on the Her-Dye@MSN. The time-course of competitive experiments with free antibody indicates that Her-Dye@MSN serves as a multivalent ligand. Moreover, Her-Dye@MSNs are internalized into cells through a receptor-mediated endocytosis and may escape from endosome to cytosol. The results reported here further support the potential of MSNs as a multifunctional smart nanocarriers for cell imaging and drug delivery.

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).

A New Strategy for Intracellular Delivery of Enzyme Using Mesoporous Silica Nanoparticles: Superoxide Dismutase

We developed mesoporous silica nanoparticle (MSN) as a multifunctional vehicle for enzyme delivery. Enhanced transmembrane delivery of a superoxide dismutase (SOD) enzyme embedded in MSN was demonstrated. Conjugation of the cell-penetrating peptide derived from the human immunodeficiency virus 1 (HIV) transactivator protein (TAT) to mesoporous silica nanoparticle is shown to be an effective way to enhance transmembrane delivery of nanoparticles for intracellular and molecular therapy. Cu,Zn-superoxide dismutase (SOD) is a key antioxidant enzyme that detoxifies intracellular reactive oxygen species, ROS, thereby protecting cells from oxidative damage. In this study, we fused a human Cu,Zn-SOD gene with TAT in a bacterial expression vector to produce a genetic in-frame His-tagged TAT-SOD fusion protein. The His-tagged TAT-SOD fusion protein was expressed in E. coli using IPTG induction and purified using FMSN-Ni-NTA. The purified TAT-SOD was conjugated to FITC-MSN forming FMSN-TAT-SOD. The effectiveness of FMSN-TAT-SOD as an agent against ROS was investigated, which included the level of ROS and apoptosis after free radicals induction and functional recovery after ROS damage. Confocal microscopy on live unfixed cells and flow cytometry analysis showed characteristic nonendosomal distribution of FMSN-TAT-SOD. Results suggested that FMSN-TAT-SOD may provide a strategy for the therapeutic delivery of antioxidant enzymes that protect cells from ROS damage.