Sudeok Kim

Delivery of shRNA using gold nanoparticle-DNA oligonucleotide conjugates as a universal carrier.

The efficient delivery of nucleic acids into mammalian cells is a central aspect of research involving cell biology and medical applications, including the clinical treatment of genetic disorders. We report an efficient small hairpin RNA (shRNA) delivery system that utilizes a single species of gold nanoparticle-DNA oligonucleotide conjugate (AuNP-DNA oligo) as a universal carrier. In vitro synthesized shRNA that is specific to the p53 gene was efficiently delivered into HEK293 and HeLa human cell lines using an AuNP-DNA oligo. The delivery resulted in an 80-90% knockdown of p53 expression. The same AuNP-DNA oligo was also efficient for the delivery of another shRNA, which is specific to the Mcl-1 gene, as well as the repression of MCL-1 expression. The knockdown efficiency of shRNA that was delivered using an AuNP-DNA oligo was comparable with that of a liposome-based shRNA delivery method. Our results offer an alternate delivery system for shRNA that can be used on any gene of interest.

Modulation of biological processes in the nucleus by delivery of DNA oligonucleotides conjugated with gold nanoparticles.

The development of a method that can efficiently deliver nucleic acids into the nucleus of living systems remains one of the key challenges for experimental and therapeutic use of nonbiological gene delivery agents. In the current study, we demonstrate a functionalized gold nanoparticle (AuNP) that can serve as a universal carrier for the delivery of DNA oligonucleotides (oligos) into the nucleus. We designed various types of DNA oligos to redirect alternative splicing of pre-mRNAs, such as MCL-1 and BCL-6, and to sequester transcriptional factors, including estrogen receptor α and p53. We successfully delivered the oligos into the nucleus, resulting in the targeted effects. In addition, injection of the antisense DNAs into a xenograft tumor in a mouse model system resulted in inhibited development of the tumor by redirecting the alternative splicing of the pre-mRNA. Our findings show that these nanoconjugates efficiently load and deliver antisense DNAs to redirect gene splicing or double-stranded DNAs to decoy gene transcription by transcriptional factors into mammalian cells and in vivo animals. Therefore, our lego-like AuNP gene delivery system can be used universally to control different biological processes by modulating nuclear gene expression events in living systems.

Gold nanoparticle-based colorimetric chiral discrimination of histidine: application to determining the enantiomeric excess of histidine

The proposed colorimetric assay system consisting of L-Pro group-functionalized gold nanoparticles (L-Pro–AuNPs) and Cu2+ ions can discriminate the absolute configuration of His and determine the enantiomeric excess of His.

Selective Colorimetric Sensor for Hg2+ Ions Using a Mixture of Thiourea Derivatives and Gold Nanoparticles Stabilized with Adenosine Triphosphate

The detection of Hg ions has attracted considerable attention in recent years because it is one of the most toxic elements on the planet and is a known environmental pollutant routinely released from coal-burning power plants, oceanic and volcanic emissions, gold mining, and solid-waste incineration. As a result, numerous optical detection methods for Hg ions have been developed based upon several strategies, including fluorogenic and chromogenic organic dyes, functional polymers, oligonucleotides, and proteins. In addition, nanomaterials, including carbon nanotubes, silica nanoparticles, quantum dots, and gold nanoparticles, have been recently studied as alternative detection methods for Hg ions. In particular, colorimetric chemosensors are attractive because they can be understood with the naked eye, in some cases at the point of use. Therefore, a lot of colorimetric sensors for Hg ions have been developed based upon chromogenic organic dyes and gold nanoparticles. Gold nanoparticles (AuNPs) are attractive scaffolds for the creation of a colorimetric sensing system of Hg ions owing to their optical properties. Gold nanoparticles are good chromophores because their extinction coefficients are 3–5 orders of magnitude higher than those of organic dye molecules. Gold nanoparticles also have unique distance-dependent optical properties that can be chemically programmed through the use of specific host compounds; DNA, etc. can induce a dramatic red-to-blue color change in the AuNPs. So far, several strategies for the detection of Hg ions have been developed, including chemically modified AuNPs, DNA functionalized AuNPs, and a mixture of oligonucleotide and unmodified AuNPs. Chemical modification methods utilize the interconnection of chemically modified AuNPs induced by the interaction between Hg ions and ligands on the AuNPs. The DNA-functionalized AuNP method and the mixture of oligonucleotides and AuNPs utilize thymine–Hg–thymine interactions; Hg ions can selectively bind in between two mismatched oligonucleotide thymines, and a measurable signal is transduced by the interaction. Unmodified AuNP-based colorimetric chemosensor methods are the simplest of these methods and can detect Hg ions in aqueous media with high sensitivity and selectivity. Most of unmodified AuNPbased colorimetric chemosensors have been utilized with the mixture of oligonucleotides and AuNPs and the high specificity of oligonucleotide interactions with Hg ions. Therefore, it is desirable to develop another approach for unmodified AuNP-based chemosensors for Hg ions. Herein, we describe a new type of unmodified AuNPbased chemosensor for Hg ions in aqueous media with high sensitivity and selectivity using a Hg-promoted desulfurization reaction of a thiourea derivative and the reactivity of thiourea with gold nanoparticles. Thiourea is readily transformed into urea by a Hg-promoted desulfurization reaction owing to the strong thiophilic affinity of Hg ions which, unlike urea, can bind readily with gold nanoparticles. In addition, many thiourea derivatives have been developed as optical chemodosimeters for Hg ions by utilizing optical changes associated with this reaction. To develop an unmodified AuNP-based chemosensor, we used adenosine-triphosphate (ATP)-stabilized AuNPs (sAuNPs) prepared by mixing citric-acid-stabilized AuNPs and ATP. The sAuNPs are more stable than citric-acid-stabilized AuNPs over a wider pH range even in high salt concentrations. Typically, sAuNPs can aggregate immediately when exposed to metal ligands, such as thiourea. Therefore, we expected thiourea derivatives to react with the sAuNPs and cause them to aggregate owing to surface changes in the sAuNPs that transform them from being hydrophilic (ATP) into being hydrophobic (thiourea derivative). This reaction results in a visible color change in the sAuNP solu[a] S. Kim, N. H. Lee, S. H. Seo, M. S. Eom, Prof. Dr. S. Ahn, Prof. Dr. M. S. Han Department of Chemistry, Chung-Ang University Seoul 156-756 (Republic of Korea) Fax: (+82) 2-825-4736 E-mail : mshan@cau.ac.kr Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000483.

Gold nanoparticle-assisted delivery of small, highly structured RNA into the nuclei of human cells.

Previous studies have shown that functionalized gold nanoparticles (AuNPs) can be used as a general platform for loading and delivering DNA oligonucleotides and short hairpin RNA to living systems. Here, we report the ability of functionalized AuNP to deliver RNA aptamers into the nuclei of human cells. An in vitro-synthesized RNA aptamer specific to the β-catenin protein was delivered into the HepG2 human cell line more efficiently via functionalized AuNP than liposome-based delivery, and resulted in nearly complete inhibition of β-catenin binding to the p50 subunit of NF-κB in the nucleus. This inhibition led to repression of NF-κB p50-dependent transcription of CRP. Also, the β-catenin aptamer in the nucleus led to down-regulation of β-catenin-mediated transcriptional activity through the TCF complex and resulted in decrease in the levels of cyclin D, and c-myc mRNA by ~47% and ~57%, respectively. In addition, we used functionalized AuNP to deliver another RNA aptamer targeted to the p50 subunit of NF-κB into the A549 human cell line, and this was sufficient to induce apoptosis of the cells. Our findings demonstrate that AuNP GDS can be used to deliver small, highly structured RNA aptamers into the nucleus of human cells where they modulate the activity of transactivators by interacting with target proteins.

Inhibition of xenograft tumor growth in mice by gold nanoparticle-assisted delivery of short hairpin RNAs against Mcl-1L

A prerequisite for the therapeutic use of small RNAs is the development of a method that can deliver them into animals. Previous studies have shown the capability of functionalized gold nanoparticles to serve as a general platform for loading and delivering DNA oligonucleotides and short hairpin RNAs (shRNAs) into cultured human cells. Here, we report the ability of the gold nanoparticle-assisted gene delivery system (AuNP-GDS) to deliver shRNA to a xenograft tumor in a mouse model. AuNP-GDS delivery of in vitro synthesized shRNA targeted to the Mcl-1L gene knocked down levels of Mcl-1L mRNA and protein by ~36% and ~26%, respectively, which were sufficient to induce apoptosis of the xenograft tumor cells and consequently inhibited the development of the tumor. We demonstrated that our lego-like AuNP-GDS, which can easily load and deliver shRNAs targeted to any gene of interest into living systems, can deliver shRNAs into xenograft tumors, leading to antitumor activity in an animal model.

Enhanced protein-mediated binding between oligonucleotide–gold nanoparticle composites and cell surfaces: co-transport of proteins and composites

The measurement of the binding force between a cell membrane and an oligonucleotide-functionalized, gold-coated tip using atomic force microscope force spectroscopy showed enhanced binding forces due to the presence of proteins in the buffer. The cellular uptake of oligonucleotide–gold nanoparticle composites was also enhanced when the composites were coated with serum proteins. Confocal microscopy image analysis of fluorescently labeled serum proteins and the oligonucleotides of the composites revealed co-transport of proteins and the composites.

Efficacy and safety of non-invasive body tightening with high-intensity focused ultrasound (HIFU)

Noninvasive skin‐tightening devices have become increasingly popular in response to increasing demand for improvements in skin laxity and tightening with minimal risk and recovery time.

Tightening effects of high-intensity focused ultrasound on body skin and subdermal tissue: a pilot study

High‐intensity focused ultrasound (HIFU) has been introduced as a new treatment modality for skin tightening through application mainly to the face and neck.