Florian L. Geyer

Superhydrophobic–Superhydrophilic Micropatterning: Towards Genome‐on‐a‐Chip Cell Microarrays

Living cells are extremely complex biological systems, and a variety of cell assays have been developed to study these systems in vitro. Cell microarrays have emerged as a promising technique that enable cell assays in a highly parallel and miniaturized manner. However, owing to cross-contamination and cell migration problems, the density of most current cell microarrays is still limited. Herein, we describe a facile method for the fabrication of arrays of superhydrophilic microspots separated by superhydrophobic barriers. We show that such arrays provide a great opportunity to solve both the cross-contamination and cell-migration problems of living cell microarrays and to enable fabrication of ultrahighdensity cell microarrays that can be used for genome-wide cell screens using a single array. The method for the preparation of arrays presented herein is based on creating a grid-like superhydrophobic pattern by UV-initiated photografting on a glass plate coated with a thin layer of superhydrophilic, biocompatible, and transparent nanoporous poly(2-hydroxyethyl methacrylateco-ethylene dimethacrylate) (HEMA-EDMA). The geometry and size of the produced superhydrophilic spots and superhydrophobic barriers can be precisely controlled by a photomask. The extreme wettability of the microspots guarantees an easy and homogeneous adsorption of the spotting solutions, while narrow superhydrophobic barriers effectively prevent cross-contamination of the spotting solutions between adjacent microspots. Cell experiments carried out with several commonly used cell lines confirmed preferential adhesion and proliferation of cells on the superhydrophilic spots and virtually no cell growth on the superhydrophobic barriers. Finally, the narrow 60 mm superhydrophobic gaps between the spots proved to be highly efficient barriers against cell migration. The aims of main applications of cell microarrays are to screen chemical or genomic 5,9] libraries or to systematically investigate the local cellular microenvironment. 10,11] Application of this technique for functional characterization of the genome using the method of reverse cell transfection to perform genome-wide gainor loss-of-function experiments has attracted exceptional attention. 7,9, 12, 13] To produce a microarray for reverse cell transfection, solutions of transfection reagents containing gelatin are printed on a solid substrate in an array pattern and dried. Then, cells are seeded on the array and the uptake of nucleic acids by the cells growing on each spot results in an array of locally transfected cells within a lawn of non-transfected cells (Figure 1A).

DropletMicroarray: facile formation of arrays of microdroplets and hydrogel micropads for cell screening applications

We describe a one-step method for creating thousands of isolated pico- to microliter-sized droplets with defined geometry and volume. Arrays of droplets are instantly formed as liquid moves along a superhydrophilic-superhydrophobic patterned surface. Bioactive molecules, nonadherent cells, or microorganisms can be trapped in the fully isolated microdroplets for high-throughput screening, or in hydrogel micropads for screening in 3D microenvironments.

Porous Polymers Based on Aryleneethynylene Building Blocks

Porous conjugated polymers are synthesized by metal-catalyzed coupling reactions. The progress for porous polymers when planar or tetrahedral building blocks are connected by alkyne units into novel materials is highlighted. The most prominent reaction for the buildup of the microporous alkyne-bridged polymers is the Sonogashira reaction, connecting alkynes to aromatic iodides or bromides. The availability of the building blocks and the potency of the Sonogashira reaction allow preparing a large variety of intrinsically porous polymeric materials, in which rigid struts connect multipronged centers. The microporous polymers are used as catalysts and as storage materials for gases and sensors. Postfunctionalization schemes, understanding of structure-property relationships, and the quest for high porosity are pertinent.

Bent N-Heteroarenes

The syntheses and optical, electronic, and structural properties of a series of bent N-heteroarenes are described. The targets were obtained by condensation reactions of substituted aromatic o-diamines with 1,2-naphthoquinone and 1,2-anthraquinone in yields between 34 and 94%; naphthoquione-based products are generally formed in higher yields.

The Radical Anion and Dianion of Tetraazapentacene.

The mono- and bis-reduction of 6,13-bis((triisopropylsilyl)ethynyl)quinoxalino[2,3-b]phenazine (1) with potassium anthracenide in THF is reported. Both the radical anion 1(.-) and the dianion 1(2-) were isolated and characterized by optical and structural (single-crystal X-ray diffraction) methods. Solutions of the radical anion 1(.-) were stable in air for several hours and characterized by EPR spectroscopy. Dianion 1(2-) is highly fluorescent and photostable.

Preparation, Properties, and Structures of the Radical Anions and Dianions of Azapentacenes

A series of diazapentacenes (5,14-diethynyldibenzo[b,i]phenazine, 6,13-diethynylnaphtho[2,3-b]phenazine) and tetraazapentacenes (7,12-diethynylbenzo[g]quinoxalino[2,3-b]quinoxaline, 6,13-diethynylquinoxalino[2,3-b]phenazine) were reduced to their radical anions and dianions, employing either potassium anthracenide or lithium naphthalenide in THF. The anionic species formed were investigated by UV-vis-NIR, fluorescence and EPR spectroscopy, spectroelectrochemistry, and quantum chemical calculations. Single crystal X-ray structures of three of their radical anions and of three of their dianions were obtained. In contrast to the acenes, the anions of the azapentacenes are persistent and, in some cases, even moderately stable toward air, and were characterized.

Growth of rylene diimide crystalline layers on aminoalkyl triethoxysilane-monolayers for organic field effect transistor applications

Macroscopically aligned, crystalline layers are a key requirement for high-performance organic field effect transistors from small molecule organic semiconductors. We investigated the crystallization behavior of n-type semiconducting naphthalene and perylene diimides at the liquid/solid/air interface as a solvent meniscus – evaporation-induced – slowly moved along the surface of a monolayer functionalized Si/SiO2. Amine-terminated, triethoxysilane based functional polar monolayers enforce highly oriented crystallization of the respective rylene diimides at the three-phase border. The electron transporting properties of the resulting crystalline layers of rylene diimides were studied in bottom gate-top electrode field effect transistors, which were shown to be improved up to two orders of magnitude over those of solution casted films. Anisotropic effects expected for crystalline devices were also revealed, which corroborated with the macroscopically oriented crystalline planes observed by polarized optical microscopy.

Synthesis and structure of tetraethynylsilane and its silylated derivatives.

The known tetrakis((trimethylsilyl)ethynyl)silane was prepared and deprotected. By using trifluoromethanesulfonic acid, the smooth stepwise desilylation of the starting material was achieved, and all of the partially protected and the fully deprotected species were isolated by sublimation. Crystal structures of all of the partially and the fully deprotected species were obtained. None of the compounds is thermally sensitive. Attempts to explosively decompose these species upon heating failed.

Fourfold Diels–Alder Reaction of Tetraethynylsilane

A series of ethynylated silanes, including tetraethynylsilane, was treated with tetraphenylcyclopentadienone at 300 °C under microwave irradiation to give the aromatized Diels-Alder adducts as sterically encumbered mini-dendrimers with up to 20 benzene rings. The sterically most congested adducts display red-shifted emission through intramolecular π-π interactions in the excited state.