Siu-Fung Lee

Enhanced cellular uptake of aminosilane-coated superparamagnetic iron oxide nanoparticles in mammalian cell lines

Purpose To compare the cellular uptake efficiency and cytotoxicity of aminosilane (SiO2-NH2)-coated superparamagnetic iron oxide (SPIO@SiO2-NH2) nanoparticles with three other types of SPIO nanoparticles coated with SiO2 (SPIO@SiO2), dextran (SPIO@dextran), or bare SPIO in mammalian cell lines. Materials and methods Four types of monodispersed SPIO nanoparticles with a SPIO core size of 7 nm and an overall size in a range of 7–15 nm were synthesized. The mammalian cell lines of MCF-7, MDA-MB-231, HT-29, RAW264.7, L929, HepG2, PC-3, U-87 MG, and mouse mesenchymal stem cells (MSCs) were incubated with four types of SPIO nanoparticles for 24 hours in the serum-free culture medium Dulbecco’s modified Eagle’s medium (DMEM) with 4.5 μg/mL iron concentration. The cellular uptake efficiencies of SPIO nanoparticles were compared by Prussian blue staining and intracellular iron quantification. In vitro magnetic resonance imaging of MSC pellets after SPIO labeling was performed at 3 T. The effect of each SPIO nanoparticle on the cell viability of RAW 264.7 (mouse monocyte/macrophage) cells was also evaluated. Results Transmission electron microscopy demonstrated surface coating with SiO2-NH2, SiO2, and dextran prevented SPIO nanoparticle aggregation in DMEM culture medium. MCF-7, MDA-MB-231, and HT-29 cells failed to show notable iron uptake. For all the remaining six cell lines, Prussian blue staining and intracellular iron quantification demonstrated that SPIO@ SiO2-NH2 nanoparticles had the highest cellular uptake efficiency. SPIO@SiO2-NH2, bare SPIO, and SPIO@dextran nanoparticles did not affect RAW 264.7 cell viability up to 200 μg Fe/mL, while SPIO@SiO2 reduced RAW 264.7 cell viability from 10 to 200 μg Fe/mL in a dose-dependent manner. Conclusion Cellular uptake efficiency of SPIO nanoparticles depends on both the cell type and SPIO surface characteristics. Aminosilane surface coating enhanced the cellular uptake efficiency without inducing cytotoxicity in a number of cell lines.

Folate-conjugated Fe3O4@SiO2@gold nanorods@mesoporous SiO2 hybrid nanomaterial: a theranostic agent for magnetic resonance imaging and photothermal therapy

In this paper, we investigated the functional imaging and targeted therapeutic properties of core@multi-shell nanoparticles composed of a superparamagnetic iron oxide (SPIO) core and gold nanorods (GNRs) in the mesoporous silica shells functionalized with folic acid (Fe3O4@SiO2@GNRs@mSiO2-FA). The as-synthesized five-component hybrid nanocomposite was revealed to have insignificant cytotoxicity. Intracellular uptake of the nanoparticles was studied in the folate receptor over-expressing human epidermoid carcinoma of the nasopharynx (KB) cells. Due to their magnetic/optical properties as well as the folate targeting potential, compared with Fe3O4@SiO2@GNRs@mSiO2 nanoparticles, higher cellular uptake efficiency was observed for Fe3O4@SiO2@GNRs@mSiO2-FA nanoparticles in KB cells. Characterizations were achieved using both dark field and magnetic resonance (MR) imaging techniques. The hyperthermia induced by Fe3O4@SiO2@GNRs@mSiO2-FA nanoparticles resulted in a higher cytotoxicity in KB cells. Thus, the Fe3O4@SiO2@GNRs@mSiO2-FA hybrid nanomaterial is an effective and promising MR imaging and photothermal therapy agent for folate-receptor over-expressing cancer cells.

Hollow superparamagnetic iron oxide nanoshells as a hydrophobic anticancer drug carrier: intracelluar pH-dependent drug release and enhanced cytotoxicity

With curcumin and doxorubicin (DOX) base as model drugs, intracellular delivery of hydrophobic anticancer drugs by hollow structured superparamagnetic iron oxide (SPIO) nanoshells (hydrodynamic diameter: 191.9 ± 2.6 nm) was studied in glioblastoma U-87 MG cells. SPIO nanoshell-based encapsulation provided a stable aqueous dispersion of the curcumin. After the SPIO nanoshells were internalized by U-87 MG cells, they localized at the acidic compartments of endosomes and lysosomes. In endosome/lysosome-mimicking buffers with a pH of 4.5-5.5, pH-dependent drug release was observed from curcumin or DOX loaded SPIO nanoshells (curcumin/SPIO or DOX/SPIO). Compared with the free drug, the intracellular curcumin content delivered via curcumin/SPIO was 30 fold higher. Increased intracellular drug content for DOX base delivered via DOX/SPIO was also confirmed, along with a fast intracellular DOX release that was attributed to its protonation in the acidic environment. DOX/SPIO enhanced caspase-3 activity by twofold compared with free DOX base. The concentration that induced 50% cytotoxic effect (CC(50)) was 0.05 ± 0.03 μg ml(-1) for DOX/SPIO, while it was 0.13 ± 0.02 μg ml(-1) for free DOX base. These results suggested SPIO nanoshells might be a promising intracellular carrier for hydrophobic anticancer drugs.

Photocytotoxicity and magnetic relaxivity responses of dual-porous γ-Fe2O3@meso-SiO2 microspheres.

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.

Efficacy and Durability in Direct Labeling of Mesenchymal Stem Cells Using Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Organosilica, Dextran, and PEG Coatings

We herein report a comparative study of mesenchymal stem cell (MSC) labeling using spherical superparamagnetic iron oxide (SPIO) nanoparticles containing different coatings, namely, organosilica, dextran, and poly(ethylene glycol) (PEG). These nanomaterials possess a similar SPIO core size of 6–7 nm. Together with their coatings, the overall sizes are 10–15 nm for all SPIO@SiO2, SPIO@dextran, and SPIO@PEG nanoparticles. These nanoparticles were investigated for their efficacies to be uptaken by rabbit bone marrow-derived MSCs without any transfecting agent. Experimentally, both SPIO@SiO2 and SPIO@PEG nanoparticles could be successfully uptaken by MSCs while the SPIO@dextran nanoparticles demonstrated limited labeling efficiency. The labeling durability of SPIO@SiO2 and SPIO@PEG nanoparticles in MSCs after three weeks of culture were compared by Prussian blue staining tests. SPIO@SiO2 nanoparticles demonstrated more blue staining than SPIO@PEG nanoparticles, rendering them better materials for MSCs labeling by direct uptake when durable intracellullar retention of SPIO is desired.

Nanoparticle-encapsulated chlorhexidine against oral bacterial biofilms

Background Chlorhexidine (CHX) is a widely used antimicrobial agent in dentistry. Herein, we report the synthesis of a novel mesoporous silica nanoparticle-encapsulated pure CHX (Nano-CHX), and its mechanical profile and antimicrobial properties against oral biofilms. Methodology/Principal Findings The release of CHX from the Nano-CHX was characterized by UV/visible absorption spectroscopy. The antimicrobial properties of Nano-CHX were evaluated in both planktonic and biofilm modes of representative oral pathogenic bacteria. The Nano-CHX demonstrated potent antibacterial effects on planktonic bacteria and mono-species biofilms at the concentrations of 50–200 µg/mL against Streptococcus mutans, Streptococcus sobrinus, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Enterococccus faecalis. Moreover, Nano-CHX effectively suppressed multi-species biofilms such as S. mutans, F. nucleatum, A. actinomycetemcomitans and Porphyromonas gingivalis up to 72 h. Conclusions/Significance This pioneering study demonstrates the potent antibacterial effects of the Nano-CHX on oral biofilms, and it may be developed as a novel and promising anti-biofilm agent for clinical use.

Nanoparticle–DNA–polymer composites for hepatocellular carcinoma cell labeling, sensing, and magnetic resonance imaging

This paper describes comparative studies and protocols in (1) self-assembling of ultrasmall superparamagnetic iron oxide nanoparticle (NP), circular plasmid DNA, and branched polyethylenimine (PEI) composites; (2) magnetofection; (3) gene delivery, (4) magnetic resonance imaging (MRI), and (5) cytotoxicity of the composites toward hepatocellular carcinoma HepG2 cells.

Increased Efficacies in Magnetofection and Gene Delivery to Hepatocellular Carcinoma Cells with Ternary Organic–Inorganic Hybrid Nanocomposites

In recent years, liver cancer (hepatocellular carcinoma) has been ranked as the leading cancer in Asia together with lung and stomach cancers. Towards the treatment of human hepatocellular carcinoma, a novel theranostic nanomaterial has yet to be developed for potential simultaneous gene transfer, drug delivery, and magnetic resonance imaging (MRI) enhancement. Superparamagnetic iron oxide nano/microparticles such as ferumoxides and ferucarbotran have been used clinically as contrast agents for MRI in liver. In light of treating human hepatocellular carcinoma, we report herein the use of ternary organic–inorganic hybrid nanocomposites PEI/DNA/NP that contain deferoxamine-coated superparamagnetic iron oxide nanoparticles (NP), circular plasmid DNA (pEGFP-C1 and pRL-CMV), and branched polyethylenimine (PEI, 25 kDa, PDI =2.5), which are potentially suitable for the proposed applications together with transfection studies in HepG2 cells. Only a small amount of branched PEI is employed for forming the stable ternary complex to reduce its cytotoxicity. Plasmid pEGFP-C1 (~4.7 kb) encodes a red-shifted variant of wild-type green fluorescence protein (GFP) for expression in mammalian cells, while pRL-CMV (~4.0 kb) encodes Renilla luciferase (RLU) for expression in various cell types. These two DNAs are commonly used as markers for studying transfection efficacies. The fluorescence/luminescence intensity is directly proportional to the amount of GFP/ RLU, which can be easily detected owing to the strong and constitutive expression of the reporters. By using two signaldetection methods, any reduction of the enhancement of PEI/DNA/NP uptake by cells can be estimated. Deferoxamine is used clinically to treat iron poisoning, as it binds ferric ions in the blood stream and enhances its elimination in urine. Ultrasmall NPs of 8–10 nm in diameter (Figure 1) were attached to deferoxamine ligand at their peripheries in three synthetic steps; their hydroxy functional groups can interact with DNA and PEI, mainly through amide hydrogen bonds and electrostatic interactions. Stable ternary organic– inorganic hybrid nanocomposites of approximately 250 nm in diameter with different component ratios have been prepared in phosphate-buffered saline (PBS) and characterized by light scattering, zeta-potential analyses, mobility tests, etc. Typical Prussian blue staining images of HepG2 cells internalized with six ternary complexes that possess different ratios of components are shown in Figure 2. According to the visual assessment of these images, the cellular uptake efficacy increases as the amount of NPs was increased from 0.1 to 1.0 mg per well. By contrast, the PEI amount of 0.2 ng gives the best cellular uptake efficacy among other amounts [a] Prof. Dr. K. C.-F. Leung, Dr. X.-M. Zhu, C.-H. Wong Department of Chemistry The Hong Kong Baptist University Kowloon Tong, Kowloon, Hong Kong SAR (P. R. China) Fax: (+852) 3411-7348 E-mail : cfleung@hkbu.edu.hk [b] Dr. C.-P. Chak, S.-F. Lee Department of Chemistry The Chinese University of Hong Kong Shatin, NT, Hong Kong SAR (P. R. China) [c] J. M. Y. Lai, K. W. Y. Sham, Prof. Dr. C. H. K. Cheng School of Biomedical Sciences and Center of Novel Functional Molecules The Chinese University of Hong Kong Shatin, NT, Hong Kong SAR (P. R. China) [d] Dr. X.-M. Zhu, Prof. Dr. Y.-X. J. Wang Department of Imaging and Interventional Radiology Prince of Wales Hospital, The Chinese University of Hong Kong Shatin, NT, Hong Kong SAR (P. R. China) [e] Prof. Dr. K. C.-F. Leung Institute of Creativity The Hong Kong Baptist University Kowloon Tong, Kowloon, Hong Kong SAR (P. R. China) [f] Prof. Dr. K. C.-F. Leung Institute of Molecular Functional Materials Areas of Excellence, University Grants Committee Hong Kong SAR (P. R. China) Figure 1. Scheme of the synthetic route to obtain PEI/DNA/NP ternary organic–inorganic hybrid nanocomposites from deferoxamine-coated superparamagnetic iron oxide nanoparticles. Reagents and conditions: a) succinic anhydride, DMF, rt, 24 h; b) N,N’-dicyclohexylcarbodiimide, N-hydroxysuccinimide, THF, rt, 24 h; and c) deferoxamine, DMF, rt, 24 h.

Surface Molecular Tailoring Using pH-Switchable Supramolecular Dendron-Ligand Assemblies

The rational design of materials with tailored properties is of paramount importance for a wide variety of biological, medical, electronic and optical applications. Here we report molecular level control over the spatial distribution of functional groups on surfaces utilizing self-assembled monolayers (SAMs) of pH-switchable surface-appended pseudorotaxanes. The supramolecular systems were constructed from a poly(aryl ether) dendron-containing a dibenzo[24]crown-8 (DB24C8) macrocycle and a thiol ligand-containing a dibenzylammonium recognition site and a fluorine end group. The dendron establishes the space (dendritic effect) that each pseudorotaxane occupies on the SAM. Following SAM formation, the dendron is released from the surface by switching off the noncovalent interactions upon pH stimulation, generating surface materials with tailored physical and chemical properties.

Azobenzene dendronized carbon nanoparticles: the effect of light antenna

Fluorescent carbon nanoparticles are grafted with azobenzene dendrons, giving unique dendronized carbon nanoparticles that exhibit an increased quantum yield by as much as ∼74% at a low concentration. Such an improvement is attributed to the strong light harvesting capability of grafted azobenzene dendrons that act as “light antenna” to collect photons and the excitons generated then traverse to adjacent central carbon nanoparticles.