Dendrimer-mediated transfer printing of DNA and RNA mircoarrays

This paper describes a new method to replicate DNA and RNA microarrays. The technique, which facilitates positioning of DNA and RNA with submicron edge resolution by microcontact printing (μCP), is based on the modification of poly(dimethylsiloxane) (PDMS) stamps with dendrimers (“dendri-stamps”). The modification of PDMS stamps with generation 5 poly(propylene imine) dendrimers (G5-PPI) gives a high density of positive charge on the stamp surface that can attract negatively charged oligonucleotides in a “layer-by-layer” arrangement. DNA as well as RNA is transfer printed from the stamp to a target surface. Imine chemistry is applied to immobilize amino-modified DNA and RNA molecules to an aldehyde-terminated substrate. The labile imine bond is reduced to a stable secondary amine bond, forming a robust connection between the polynucleotide strand and the solid support. Microcontact printed oligonucleotides are distributed homogeneously within the patterned area and available for hybridization. By using a robotic spotting system, an array of hundreds of oligonucleotide spots is deposited on the surface of a flat, dendrimer-modified stamp that is subsequently used for repeated replication of the entire microarray by microcontact printing. The printed microarrays are characterized by homogeneous probe density and regular spot morpholog

Religion, politics, and performance in the Congo - Gesture and power: Religion, nationalism, and everyday performance in Congo. By Yolanda Covington-Ward. Durham and London: Duke University Press, 2016

Chemical modification of the surface of a stamp used for microcontact printing (uCP) is interesting for controling the surface properties, such as the hydrophilicity. To print polar inks, plasma polymerization of allylamine (PPAA) was employed to render the surface of poly(dimethylsiloxane) (PDMS), polyolefin plastomers (POP), and Kraton elatomeric stamps hydrophilic for long periods of time. A thin PPAA film of about 5 nm was deposited on the stamps, which increased the hydrophilicity, and which remained stable for at least several months. These surface-modified stamps were used to transfer polar inks by .CP. The employed uCP schemes are as follows: (a) a second generation of dendritic ink having eight dialkyl sulfide end groups to fabricate patterns on gold substrates by positive uCP, (b) fluorescent guest molecules on B-cyclodextrin (B-CD) printboards on glass employing host-guest recognition, and (c) Lucifer Yellow ethylenediamine resulting in covalent patterning on an aldehyde-terminated glass surface. All experiments resulted in an excellent performance of all three PPAA-coated stamp materials to transfer the polar inks from the stamp surface to gold and glass substrates by uCP, even from aqueous solutions

Organic and Macromolecular Films and Assemblies as (Bio) reactive Platforms: From Model Studies on Structure-Reactivity Relationships to Submicrometer Patterning

In this contribution we review our recent progress in studies that aim at the understanding of the relationship between structure and surface reactivity of organic thin films on the one hand, and at the micro- and nanofabrication of bioreactive or biocompatible platforms on the other hand. Self-assembled monolayers (SAMs) of n,n′-dithiobis(N-hydroxysuccinimidyl-n-alkanoate) exposing NHS reactive ester groups were studied as model systems for immobilization reactions of DNA, proteins, and receptors. Reaction kinetics and activation energies were determined quantitatively at length scales ranging from millimeters down to nanometers using, for example, surface infrared spectroscopy and in situ inverted chemical force microscopy (iCFM), respectively. The increase in conformational order with increasing alkane segment length was found to result in reduced reactivity due to steric crowding. This drawback of highly organized monolayer architectures and the inherently limited loading can be circumvented by utilizing well-defined macromolecular thin films. Using amine-terminated polyamidoamine (PAMAM) dendrimers immobilized via soft lithography, as well as scanning probe lithography (SPL) approaches (dip-pen nanolithography, DPN) on NHS ester surfaces, robust micrometer and submicrometer patterned (bio)reactive surfaces, which allow one to achieve high molecular loading in coupling reactions for chip-based assays and sensor surfaces, were fabricated. Covalent coupling afforded the required robustness of the patterned assemblies. Finally, we address micro- and nanopatterned bilayer-based systems. SPL was applied in order to fabricate nanoscale biocompatible supramolecular architectures on solid supports. The adsorption of vesicles onto lipid bilayers was spatially controlled and directed in situ with nanometer-scale precision using SPL. This methodology, which provides a platform for research on proteins incorporated in the lipid bilayers comprising the vesicles, does not require that the vesicles are chemically labeled in order to guide their deposition