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The generation of chemically activated glass surfaces is of increasing interest for the production of microarrays containing DNA, proteins, and low-molecular-weight components. We here report on a novel surface chemistry for highly efficient activation of glass slides. Our method is based on the initial modification of glass with primary amino groups using a protocol, specifically optimized for high aminosilylation yields, and in particular, for homogeneous surface coverages. In a following step the surface amino groups are activated with a homobifunctional linker, such as disuccinimidylglutarate (DSG) or 1,4-phenylenediisothiocyanate (PDITC), and then allowed to react with a starburst dendrimer that contains 64 primary amino groups in its outer sphere. Subsequently, the dendritic monomers are activated and crosslinked with a homobifunctional spacer, either DSG or PDITC. This leads to the formation of a thin, chemically reactive polymer film, covalently affixed to the glass substrate, which can directly be used for the covalent attachment of amino-modified components, such as oligonucleotides. The resulting DNA microarrays were studied by means of nucleic acid hybridization experiments using fluorophor-labeled complementary oligonucleotide targets. The results indicate that the novel dendrimer-activated surfaces display a surface coverage with capture oligomers about twofold greater than that with conventional microarrays containing linear chemical linkers. In addition, the experiments suggest that the hybridization occurs with decreased steric hindrance, likely a consequence of the long, flexible linker chain between the surface and the DNA oligomer. The surfaces were found to be resistant against repeated alkaline regeneration procedures, which is likely a consequence of the crosslinked polymeric structure of the dendrimer film. The high stability allows multiple hybridization experiments without significant loss of signal intensity. The versatility of the dendrimer surfaces is also demonstrated by the covalent immobilization of streptavidin as a model protein.

Biological compartmentalization is a fundamental principle of life that allows cells to metabolize, propagate, or communicate with their environment. Much research is devoted to understanding this basic principle and to harness biomimetic compartments and catalytic cascades as tools for technological processes. This Review summarizes the current state-of-the-art of these developments, with a special emphasis on length scales, mass transport phenomena, and molecular scaffolding approaches, ranging from small cross-linkers over proteins and nucleic acids to colloids and patterned surfaces. We conclude that the future exploration and exploitation of these complex systems will largely benefit from technical solutions for the integrated, machine-assisted development and maintenance of a next generation of biotechnological processes. These goals should be achievable by implementing microfluidics, robotics, and added manufacturing techniques supplemented by theoretical simulations as well as computer-aided process modeling based on big data obtained from multiscale experimental analyses.

Spatially controlled assembly of enzyme conjugates can be applied to signal amplification systems for biosensors, or synthesis of novel catalysts for enzyme process technology. Artificial bienzymic systems comprised of two enzymes, NAD(P)H‐FMN oxidoreductase and luciferase (represented as blue and orange spheres, respectively, in the schematic representation) were assembled by means of DNA hybridization and streptavidin–biotin interaction.

Supramolecular aggregates of DNA, RNA, streptavidin, immunoglobulin, and nanocrystalline metal clusters can be generated by self-assembly on the basis of oligonucleotide hybridization (shown schematically). Following selective immunosorption on surface-immobilized antigen, the biometallic hybrid is detectable by electron microscopy.

Structural DNA nanotechnology [1,2] and the technique of DNA origami [3] enable the rapid generation of a plethora of complex self-assembled nanostructures. [4][5][6] Since DNA molecules themselves display limited chemical, optical, and electronic functionality, it is of utmost importance to devise methods to decorate DNA scaffolds with functional moieties to realize applications in sensing, catalysis, and device fabrication. Protein functionalization is particulary desirable because it allows exploitation of an almost unlimited variety of functional elements which nature has evolved over billions of years.[7] The delicate architecture of proteins has resulted in no generally applicable method being currently available to selectively couple these components on DNA scaffolds, and thus approaches used so far are based on reversible antibodyantigen interactions, [8,9] aptamer binding, [10,11] nucleic acid hybridization of DNA-tagged proteins, [12,13] or predominantly biotin-streptavidin (STV) interactions. [14][15][16][17][18][19] We demonstrate here that DNA nanostructures can be site-specifically decorated with several different proteins by using coupling systems orthogonal to the biotin-STV system. In particular, benzylguanine (BG) and chlorohexane (CH) groups incorporated in DNA origami have been used as suicide ligands for the site-specific coupling of fusion proteins containing the self-labeling protein tags O 6 -alkylguanine-DNA-alkyltransferase (hAGT), which is often referred to as "Snap-tag", [20] or haloalkane dehalogenase, which is also known as "HaloTag".[21] By using various model proteins we demonstrate the general applicability of this approach for the generation of DNA superstructures that are selectively decorated with multiple different proteins.To realize orthogonal protein immobilization on DNA origami using self-ligating protein tags, we chose the Snap-tag, developed by Johnsson and co-workers, [20] and the commercially available HaloTag [21] system. The respective smallmolecule suicide tags (O 6 -benzylguanine (BG) and 5-chlorohexane (CH)) for both self-labeling protein tags are readily available as amino-reactive N-hydroxysuccinimide (NHS) derivatives (BG-NHS and CH-NHS; Figure 1 a). Complete derivatization of alkylamino-modified oligonucleotides was achieved by coupling with 30 molar equivalents of BG-NHS or CH-NHS, as indicated by electrophoretic analysis (Figure 1 b). To gain access to fusion proteins bearing the complementary Snap-and Halo-protein tags, we constructed expression plasmids by genetic fusion of the genes encoding the protein of interest (POI) and Snap-tag or HaloTag (see the Supporting Information). As model POIs we chose the fluorescent proteins enhanced yellow fluorescent protein (EYFP) [22] and mKate, [23] the enzymes cytochrome C peroxidase (CCP) [24] and esterase 2 from Alicyclobacillus acidocaldarius thermos (EST2), [25] to which the self-labeling tags were fused at the C terminus (POI-Snap or POI-Halo, respectively). In addition, the bispecific Halo-Snap fusion protein...

Rothemund's "scaffolded DNA origami" technique [6] dramatically simplified the fabrication of finite DNA nanostructures. In a simple and fast "one-pot" reaction, hundreds of short oligonucleotides, referred to as "staple strands," are used to direct the folding path of a kilobase long circular single-stranded DNA (ssDNA) "scaffold" into an arbitrary shape held together