Photolithographische Immobilisierung von Biopolymeren auf festen Trägern

Electroless Deposition of Nickel on Photografted Polymeric Microscale Patterns

This report demonstrates the electroless deposition of Ni onto micropatterns of poly (acrylic acid) (PAA) photografted to phthalimide-terminated self-assembled monolayers (SAMs). PAA is spin-coated onto phthalimide SAMs and covered with a photomask. UV irradiation selectively binds PAA to exposed regions of the surface, allowing PAA on unexposed regions to be rinsed off. A Pd catalyst is then selectively adsorbed to regions of the surface where PAA is bound. The adsorbed catalyst selectively initiates Ni plating upon immersion of the substrate into a Ni(SO₄ ) bath.

Chemical strategies for generating protein biochips

Protein biochips are at the heart of many medical and bioanalytical applications. Increasing interest has been focused on surface activation and subsequent functionalization strategies for immobilizing these biomolecules. Different approaches using covalent and noncovalent chemistry are reviewed; particular emphasis is placed on the chemical specificity of protein attachment and on retention of protein function. Strategies for creating protein patterns (as opposed to protein arrays) are also outlined. An outlook on promising and challenging future directions for protein biochip research and applications is also offered.

Synthesis, Characterization, and X-ray Structure Determination of [Au18(P)2(PPh)4(PHPh)(dppm)6]Cl3

The reaction of [(AuCl)2dppm] (dppm=Ph2PCH2PPh2) with PhP(SiMe3)2 and P(SiMe3)3 leads to the formation of the gold cluster compound [Au18(P)2(PPh)4(PHPh)(dppm)6]Cl3 (1). The crystal structure investigation shows a central Au7P2 unit formed by two P centered gold tetrahedra sharing the central gold corner. This central unit is surrounded by a 10-membered Au5P5 ring which, together with the remaining six gold atoms, builds two Au4P rectangular and two Au3P trigonal pyramids. The different structure motifs are connected by the phosphine ligands. The compound has been characterized using microanalysis, IR spectroscopy, ESI-MS, and 31P NMR techniques. Luminescence measurements have also been carried out.

Photons to illuminate the universe of sugar diversity through bioarrays

In this mini-review, we summarize the photochemical approaches for developing high-throughput carbohydrate microarray technologies. Newly established methods for photo-immobilizing unmodified monosaccharides, oligosaccharides and polysaccharides onto photoactive surfaces and coupling of photoactive carbohydrates onto polymer surfaces are reviewed.

Enzyme−Nanoparticle Functionalization of Three-Dimensional Protein Scaffolds

Various surface modification techniques have been developed for patterning functional biomolecules in two dimensions, allowing enzymes, antibodies, and other compounds to be localized for applications in bioanalysis and bioengineering. Here, we report a strategy for extending high-resolution patterning of biomolecules to three dimensions. In this approach, three-dimensional protein scaffolds are created by a direct-write process in which multiphoton excitation promotes photochemical cross-linking of protein molecules from aqueous solution within specified volume elements. After scaffold fabrication, protein microstructures are functionalized with enzyme-gold nanoparticle conjugates via a targeting process based in part on electrostatic attraction between the low-isoelectric-point enzyme and the microstructure, fabricated from high-isoelectric-point proteins. High signal-to-background ratios (approximately 20:1) are demonstrated for fluorescent product streams created by dephosphorylation of the fluorogenic compound, fluorescein diphosphate, at microstructures decorated with alkaline phosphatase-gold nanoparticle conjugates. We also demonstrate feasibility for using such structures to quantify substrate concentrations in flowing streams with low-micromolar detection limits and to create sensor suites based on both enzyme-nanoparticle functionalization and intrinsic enzymatic activity of protein scaffolds. These topographically complex sensors and dosing sources have potential applications in microfluidics, sensor array fabrication, and real-time chemical modification of cell culture environments.

Photochemical micropatterning of carbohydrates on a surface

In this report, we demonstrate a versatile method for the immobilization and patterning of unmodified carbohydrates onto glass substrates. The method employs a novel self-assembled monolayer to present photoactive phthalimide chromophores at the air-monolayer interface. Upon exposure to UV radiation, the phthalimide end-groups graft to surface-adsorbed carbohydrates, presumably by a hydrogen abstraction mechanism followed by radical recombination to form a covalent bond. Immobilized carbohydrate thin films are evidenced by fluorescence, ellipsometry and contact-angle measurements. Surface micropatterns of mono-, oligo-, and polysaccharides are generated by exposure through a contact photomask and are visualized by condensing water onto the surface. The efficiency of covalent coupling is dependent on the thermodynamic state of the surface. The amount of surface-grafted carbohydrate is enhanced when carbohydrate surface interactions are increased by the incorporation of amine-terminated molecules into the monolayer. Glass substrates modified with mixed monolayers of this nature are used to construct carbohydrate microarrays by spotting the carbohydrates with a robot and subsequently illuminating them with UV light to covalently link the carbohydrates. Surface-immobilized polysaccharides display well-defined antigenic determinants for antibody recognition. We demonstrate, therefore, that this novel technology combines the ability to create carbohydrate microarrays using the current state-of-the-art technology of robotic microspotting and the ability to control the shape of immobilized carbohydrate patterns with a spatial resolution defined by the UV wavelength and a shape defined by a photomask.

Bioorganic applications of semisynthetic DNA-protein conjugates

Semisynthetic DNA-protein conjugates are versatile molecular tools useful, for instance, in the self-assembly of high-affinity reagents for immunological detection assays, the fabrication of highly functionalized laterally microstructured biochips, and the biomimetic "bottom-up" synthesis of nanostructured supramolecular devices. This concept paper summarizes the current state-of-the-art concerning the synthesis, characterization, and applications of such hybrid molecules, and also draws perspectives on future developments.