Min Sik Eom

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.

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.

High-Throughput Screening Protocol for the Coupling Reactions of Aryl Halides Using a Colorimetric Chemosensor for Halide Ions

Mercury complex of 4-(2-pyridylazo)resorcinol (PAR-2Hg(2+)), a halide-ion chemosensor, was prepared and its efficiency as a tool for high-throughput screening (HTS) of transition-metal-catalyzed coupling reactions was investigated. It showed a high selectivity for halide ions. When the PAR-2Hg(2+) complex was used in the Suzuki coupling reaction and C-H activated coupling reaction with aryl bromides, the quantitative and qualitative conversions of aryl halides were obtained from the reaction mixture color change.

Paper-Based Colorimetric Sensor System for High-Throughput Screening of C−H Borylation

A paper-based colorimetric sensor system (PBCSS) was developed to detect the amount of bis(pinacolato)diboron (B2 Pin2 ) and applied as a high-throughput screening protocol in Ir-catalyzed C-H borylation. First, 96 ligands were screened for the borylation of benzene, and then 12 of them were selected and tested for five substrates. These reaction mixtures were spotted in the PBCSS, showing a blue-violet color. The value of the gray scale of each reaction was obtained from these colored spots and converted to the extent of conversion of B2 Pin2 . The extents of conversion of B2 Pin2 obtained from the PBCSS showed good correlation with those obtained from gas chromatography analysis. In addition, the modified conversion using blank data showed good correlation with the yield of products.