Hee-Kyung Na

Facile Synthesis of Monodispersed Mesoporous Silica Nanoparticles with Ultralarge Pores and Their Application in Gene Delivery

Among various nanoparticles, the silica nanoparticle (SiNP) is an attractive candidate as a gene delivery carrier due to advantages such as availability in porous forms for encapsulation of drugs and genes, large surface area to load biomacromolecules, biocompatibility, storage stability, and easy preparation in large quantity with low cost. Here, we report on a facile synthesis of monodispersed mesoporous silica nanoparticles (MMSN) possessing very large pores (>15 nm) and application of the nanoparticles to plasmid DNA delivery to human cells. The aminated MMSN with large pores provided a higher loading capacity for plasmids than those with small pores (∼2 nm), and the complex of MMSN with plasmid DNA readily entered into cells without supplementary polymers such as cationic dendrimers. Furthermore, MMSN with large pores could efficiently protect plasmids from nuclease-mediated degradation and showed much higher transfection efficiency of the plasmids encoding luciferase and green fluorescent protein (pLuc, pGFP) compared to MMSN with small pores (∼2 nm).

Quantitative and Multiplexed MicroRNA Sensing in Living Cells Based on Peptide Nucleic Acid and Nano Graphene Oxide (PANGO)

MicroRNA (miRNA) is an important small RNA which regulates diverse gene expression at the post-transcriptional level. miRNAs are considered as important biomarkers since abnormal expression of specific miRNAs is associated with many diseases including cancer and diabetes. Therefore, it is important to develop biosensors to quantitatively detect miRNA expression levels. Here, we develop a nanosized graphene oxide (NGO) based miRNA sensor, which allows quantitative monitoring of target miRNA expression levels in living cells. The strategy is based on tight binding of NGO with peptide nucleic acid (PNA) probes, resulting in fluorescence quenching of the dye that is conjugated to the PNA, and subsequent recovery of the fluorescence upon addition of target miRNA. PNA as a probe for miRNA sensing offers many advantages including high sequence specificity, high loading capacity on the NGO surface compared to DNA and resistance against nuclease-mediated degradation. The present miRNA sensor allowed the detection of specific target miRNAs with the detection limit as low as ~1 pM and the simultaneous monitoring of three different miRNAs in a living cell.

Synergistic Effect of Graphene Oxide/MWCNT Films in Laser Desorption/Ionization Mass Spectrometry of Small Molecules and Tissue Imaging

Matrix-assisted laser desorption/ionization mass spectrometry has been considered an important tool for various biochemical analyses and proteomics research. Although addition of conventional matrix efficiently supports laser desorption/ionization of analytes with minimal fragmentation, it often results in high background interference and misinterpretation of the spatial distribution of biomolecules especially in low-mass regions. Here, we show design, systematic characterization, and application of graphene oxide/multiwalled carbon nanotube-based films fabricated on solid substrates as a new matrix-free laser desorption/ionization platform. We demonstrate that the graphene oxide/multiwalled carbon nanotube double layer provides many advantages as a laser desorption/ionization substrate, such as efficient desorption/ionization of analytes with minimum fragmentation, high salt tolerance, no sweet-spots for mass signal, excellent durability against mechanical and photoagitation and prolonged exposure to ambient conditions, and applicability to tissue imaging mass spectrometry. This platform will be widely used as an important tool for mass spectrometry-based biochemical analyses because of its outstanding performance, long-term stability, and cost effectiveness.

Efficient functional delivery of siRNA using mesoporous silica nanoparticles with ultralarge pores.

Among various nanoparticles, mesoporous silica nanoparticles (MSNs) have attracted extensive attention for developing efficient drug-delivery systems, mostly due to their high porosity and biocompatibility. However, due to the small pore size, generally below 5 nm in diameter, potential drugs that are loaded into the pore have been limited to small molecules. Herein, a small interfering RNA (siRNA) delivery strategy based on MSNs possessing pores with an average diameter of 23 nm is presented. The siRNA is regarded as a powerful gene therapeutic agent for treatment of a wide range of diseases by enabling post-transcriptional gene silencing, so-called RNA interference. Highly efficient, sequence-specific, and technically very simple target gene knockdown is demonstrated using MSNs with ultralarge pores of size 23 nm in vitro and in vivo without notable cytotoxicity.

Influence of Surface Functionalization on the Growth of Gold Nanostructures on Graphene Thin Films

We developed a surface-chemistry-based approach to investigating the influence of surface functionalization on the growth of gold nanostructures on graphene thin films by utilizing various pyrene derivatives presenting different functional groups. Among the surface-modifying molecules, decylpyrene (DP) yielded the highest content of gold rods (average 22 +/- 4%) among gold nanostructures on graphene films when a graphene surface was pretreated with DP prior to gold nanostructure growth. The improved yield of gold rods on graphene thin films enhanced several physical properties of graphene such as the electrical conductivity and Raman signals by 6.3- and 14.7-fold, respectively.

One‐Pot Synthesis of Multifunctional Au@Graphene Oxide Nanocolloid Core@Shell Nanoparticles for Raman Bioimaging, Photothermal, and Photodynamic Therapy

The paper reports a facile one-pot synthesis of core@shell nanoparticles (NPs) composed of Au core and graphene oxide nanocolloid (GON) shell. Unique properties of Au NPs and GON can be incorporated into a single nanohybrid structure to provide desirable functions for theranosis such as localized surface plasmon resonance, Raman scattering, amphiphilic surface, and photothermal conversion. Synthesis of Au@GON NPs is achieved by simple one-pot reaction in aqueous phase utilizing GON as a reducing and stabilizing agent without any additional reducing agent. The zinc phthalocyanine, a photosensitizer, loaded Au@GON NPs show excellent multifunctional properties for combinational treatment of photothermal and photodynamic therapy in addition to Raman bioimaging with low cytotoxicity.

Direct cellular delivery of human proteasomes to delay tau aggregation

The 26S proteasome is the primary machinery that degrades ubiquitin (Ub)-conjugated proteins, including many proteotoxic proteins implicated in neurodegeneraton. It has been suggested that the elevation of proteasomal activity is tolerable to cells and may be beneficial to prevent the accumulation of protein aggregates. Here we show that purified proteasomes can be directly transported into cells through mesoporous silica nanoparticle-mediated endocytosis. Proteasomes that are loaded onto nanoparticles through non-covalent interactions between polyhistidine tags and nickel ions fully retain their proteolytic activity. Cells treated with exogenous proteasomes are more efficient in degrading overexpressed human tau than endogenous proteasomal substrates, resulting in decreased levels of tau aggregates. Moreover, exogenous proteasome delivery significantly promotes cell survival against proteotoxic stress caused by tau and reactive oxygen species. These data demonstrate that increasing cellular proteasome activity through the direct delivery of purified proteasomes may be an effective strategy for reducing cellular levels of proteotoxic proteins.

Deoxyribozyme-loaded nano-graphene oxide for simultaneous sensing and silencing of the hepatitis C virus gene in liver cells

The multifunctional DNAzyme (Dz) delivery system is developed based on nano-sized graphene oxide (nGO) for simultaneous detection and knockdown of the target gene. The Dz/nGO complex system allowed convenient monitoring of HCV mRNA in living cells and silencing of the HCV gene expression by Dz-mediated catalytic cleavage concurrently.

Cytoprotective effects of graphene oxide for mammalian cells against internalization of exogenous materials

To date, graphene oxide (GO), an oxidized version of graphene, has been utilized in many research areas including bioapplications such as drug delivery and bioanalysis. Unlike other spherical or polygonal nanomaterials, GO exhibits a sheet-like structure, which in itself suggests interesting applications based on its shape. Here we show that GO can protect cells from internalization of toxic hydrophobic molecules, nanoparticles, and nucleic acids such as siRNA and plasmid DNA by interacting with cell surface lipid bilayers without noticeably reducing cell viability. Furthermore, the cytoprotective effect of GO against the internalization of extracellular materials enabled spatial control over gene transfection through region-selective gene delivery only into GO-untreated cells, and not into the GO-treated cells.

MicroRNA‐Responsive Drug Release System for Selective Fluorescence Imaging and Photodynamic Therapy In Vivo

Photodynamic therapy (PDT) is a noninvasive strategy to treat diseases by light-triggered activation of a photosensitizer (PS). One aim of the recent researches on PDT is to overcome the limitation of conventional PDT by improving selective activation of PS on targeted region. Here, a microRNA (miRNA)-responsive drug activation system is developed which focuses on the role of endogenous miRNA as an internal cancer specific stimulus for initiating drug release in cancer treatment. The present system consists of PS chlorin e6 (Ce6) conjugated to peptide nucleic acid (PNA) having complementary sequence to cancer specific miRNA and dextran coated reduced graphene oxide nanocolloid (Dex-RGON). In the presence of oncogenic miR-21 in cancer cells, Ce6-PNA drug gets hybridized with miR-21, resulting in the release of Ce6-PNA from Dex-RGON and subsequent recovery of Ce6 fluorescence and activation of Ce6 as a photosensitizer under near IR irradiation. It is demonstrated that the Ce6-PNA/Dex-RGON complex shows sequence-specific fluorescence in response to miR-21 and selective cytotoxic effect for tumor growth inhibition. The present study will pave a new way for utilizing PDT in cancer treatment with tightly regulated activation of a photosensitizer by oncogenic miRNA as an internal stimulus to reduce potential risk associated with conventional PDT.