Controlling Geometry and Flow Through Bacterial Bridges on Patterned Lubricant‐Infused Surfaces (pLIS)

Spatial control of bacteria and biofilms on surfaces is necessary to understand the biofilm formation and the social interactions between bacterial communities, which could provide useful hints to study the biofilm‐involved diseases. Here patterned lubricant‐infused surfaces (pLIS) are utilized to fabricate connective structures named “bacterial bridges” between bacterial colonies of Pseudomonas aeruginosa by a simple dewetting method. It is demonstrated that the bacteria attached to hydrophilic areas and bacteria precipitated on lubricant infused borders both contribute to the formation of bacterial bridges. The geometry and distribution of bridges can be controlled using predesigned superhydrophobic–hydrophilic patterns. It is demonstrated that bacterial bridges connecting bacteria colonies act as bio‐microfluidic channels and can transport liquids, nutrients, and antibacterial substances between neighboring bacteria clusters. Thus, bacterial bridges can be used to study formation, spreading, and development of bacterial colonies, and communication within and between isolated biofilms

Elimination of Domain Boundaries Accelerates Diffusion in MOFs by an Order of Magnitude: Monolithic Metal‐Organic Framework Thin Films Epitaxially Grown on Si(111) Substrates

Many properties of the emerging class of metal-organic frameworks (MOFs) depend crucially on defect concentrations, as in case of other solids. In order to provide reference systems with nearly perfect structure and low defect density, a procedure to grow MOFs epitaxially on cm-sized Si(111) single crystals is developed. The crystalline metal-organic thin films are in high registry with the substrate\u27s crystal lattice, as demonstrated by synchrotron-based grazing incidence X-ray diffraction (GI-XRD) experiments. The corresponding reduction of MOF defect density is shown to have striking effects on the properties of these porous frameworks. The most pronounced difference concerns mass transport. An increase in the diffusion coefficient of guest molecules by one order of magnitude relative to the same MOF materials with normal defect densities is observed

Bacterial decontamination of process liquids and paints in E-coating lines by pulsed electric field treatment

Cultivation-based and DNA-based methods for determining the bacterial load and the composition of the bacterial spectrum have been successfully established for media in electrodip painting, and used for the detailed analysis of the contamination situation in an E-coating system of an automobile plant in Germany. Dominating representatives of the genus Microbacterium spp., the orders Burkholderiales and Pseudomonadales, the family Cytophagaceae and the genera Corynebacterium spp., Sphingomonas spp., and Stenotrophomonas spp. were used for inactivation experiments. Different pulsed electric field (PEF) parameters were studied for an effective and target-directed inactivation of defined bacterial suspensions containing mixtures of Gram-positive as well as Gram-negative bacteria, but also single species suspensions in adequate liquids. PEF treatment with pulse durations longer than 1.0 ls effectively killed bacteria even in low conductivity media, regardless of whether the pulses were unipolar or bipolar, indicating that the choice of pulse shape does not limit the design of the PEF system. Model calculations showed that for efficient treatment in bypass mode, a high treatment flow rate is required rather than a high inactivation efficiency of the PEF treatment. By using specific treatment parameters, such as bipolar pulses of 50 k Vcm1 and a treatment energy of 40 J mL1 , a significant reduction in both Gram-negative and Gram-positive bacteria (> 2 log 10 reduction) can be achieved while minimizing electrode corrosion and coating degradation. PEF treatment proves to be an effective alternative to the use of biocides in an E-coating system and can help maintain a bacteriostatic environment in the system by operating at different points, in transfer flow or bypass mode, ensuring biocide-free operation

Reactive block copolymers for patterned surface immobilization with sub-30 nm spacing

Phase-segregating block copolymers are powerful platforms for nanofabrication, particularly when employed as lithographic mask precursors. Surface-reactive polymeric films with distinct sub-30 nm domains are also proposed as covalent docking platforms for scalable, high-resolution molecular patterned immobilization. Here, the well-known self-assembling polystyrene-block-polyisoprene system is the starting point to produce a small library of derivatives with distinct reactive pendant groups (halide, azide, pentafluorophenylalkyl) by nitroxide-mediated radical polymerization. We find that controlling film thickness is crucial to obtain a perpendicular lamellar morphology and that the presence of the functional groups has a limited impact on self-assembly, yet may influence characteristic domain dimensions. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) are utilized in concert to assess the phase behavior of the polymers and the surface features of the nanostructures. As a proof-of-concept for the surface reactivity, click chemistry-driven immobilization of a model water-soluble polymer is evidenced by X-ray photoelectron spectroscopy (XPS) and preservation of the underlying morphology is investigated by AFM

Synthesis, Transfer, and Gas Separation Characteristics of MOF-Templated Polymer Membranes

This paper discusses the potential of polymer networks, templated by crystalline metal–organic framework (MOF), as novel selective layer material in thin film composite membranes. The ability to create mechanically stable membranes with an ultra-thin selective layer of advanced polymer materials is highly desirable in membrane technology. Here, we describe a novel polymeric membrane, which is synthesized via the conversion of a surface anchored metal–organic framework (SURMOF) into a surface anchored gel (SURGEL). The SURGEL membranes combine the high variability in the building blocks and the possibility to control the network topology and membrane thickness of the SURMOF synthesis with high mechanical and chemical stability of polymers. Next to the material design, the transfer of membranes to suitable supports is also usually a challenging task, due to the fragile nature of the ultra-thin films. To overcome this issue, we utilized a porous support on top of the membrane, which is mechanically stable enough to allow for the easy membrane transfer from the synthesis substrate to the final membrane support. To demonstrate the potential for gas separation of the synthesized SURGEL membranes, as well as the suitability of the transfer method, we determined the permeance for eight gases with different kinetic diameters

Photo‐Arbuzov Reactions as a Broadly Applicable Surface Modification Strategy

Chemical vapor deposition (CVD) polymerization is a commonly used approach in surface chemistry, providing a substrate-independent platform for bioactive surface functionalization strategies. This work investigates the Arbuzov reaction of halogenated polymer coatings readily available via CVD polymerization, using poly(4-chloro-para-xylylene) (Parylene C) as a model substance. Postpolymerization modification of these coatings via catalyst-free and UV-induced Arbuzov reaction using phosphites results in phosphonate-functionalized polymers. The combination of infrared reflection-absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) provides detailed insights into the reaction progress. Time-dependent studies suggest that the non-polar phosphites penetrate deep into the CVD films and react with the polymer film. In addition, ToF-SIMS, scanning electron microscopy (SEM), and atomic force microscopy (AFM) confirm spatial control of the reaction, resulting in localized chemical and topographical surface modification, recognizable by changes in interference color, fluorescence, and wettability. Preliminary 3D fluorescence spectroscopy investigations indicate tunable near-infrared emission of these polymer films. This work is the first step toward generating multifunctional polymer coatings based on chemically modifiable, CVD polymers with potential applications in biomaterials, sensors, or optoelectronics

Fast and efficient synthesis of microporous polymer nanomembranes via light-induced click reaction

Conjugated microporous polymers (CMPs) are materials of low density and high intrinsic porosity. This is due to the use of rigid building blocks consisting only of lightweight elements. These materials are usually stable up to temperatures of 400 °C and are chemically inert, since the networks are highly crosslinked via strong covalent bonds, making them ideal candidates for demanding applications in hostile environments. However, the high stability and chemical inertness pose problems in the processing of the CMP materials and their integration in functional devices. Especially the application of these materials for membrane separation has been limited due to their insoluble nature when synthesized as bulk material. To make full use of the beneficial properties of CMPs for membrane applications, their synthesis and functionalization on surfaces become increasingly important. In this respect, we recently introduced the solid liquid interfacial layer-by-layer (LbL) synthesis of CMP-nanomembranes via Cu catalyzed azide–alkyne cycloaddition (CuAAC). However, this process featured very long reaction times and limited scalability. Herein we present the synthesis of surface grown CMP thin films and nanomembranes via light induced thiol–yne click reaction. Using this reaction, we could greatly enhance the CMP nanomembrane synthesis and further broaden the variability of the LbL approach

How to Show the Real Microbial Biodiversity? A Comparison of Seven DNA Extraction Methods for Bacterial Population Analyses in Matrices Containing Highly Charged Natural Nanoparticles

A DNA extraction that comprises the DNA of all available taxa in an ecosystem is an essential step in population analysis, especially for next generation sequencing applications. Many nanoparticles as well as naturally occurring clay minerals contain charged surfaces or edges that capture negatively charged DNA molecules after cell lysis within DNA extraction. Depending on the methodology of DNA extraction, this phenomenon causes a shift in detection of microbial taxa in ecosystems and a possible misinterpretation of microbial interactions. With the aim to describe microbial interactions and the bio-geo-chemical reactions during a clay alteration experiment, several methods for the detection of a high number of microbial taxa were examined in this study. Altogether, 13 different methods of commercially available DNA extraction kits provided by seven companies as well as the classical phenol-chloroform DNA extraction were compared. The amount and the quality of nucleic acid extracts were determined and compared to the amplifiable amount of DNA. The 16S rRNA gene fragments of several taxa were separated using denaturing gradient gel electrophoresis (DGGE) to determine the number of different species and sequenced to get the information about what kind of species the microbial population consists of. A total number of 13 species was detected in the system. Up to nine taxa could be detected with commercially available DNA extraction kits while phenol-chloroform extraction lead to three detected species. In this paper, we describe how to combine several DNA extraction methods for the investigation of microbial community structures in clay.BIOTON, German Federal Ministry of Education and Researc

Single-chain folding of diblock copolymers driven by orthogonal H-donor and acceptor units

We report the precision single-chain folding of narrow dispersity diblock copolymers via pairwise orthogonal multiple hydrogen bonding motifs and single chain selected point folding. Well-defined linear polystyrene (PS) and poly(n-butyl acrylate) (PnBA) carrying complementary recognition units have been synthesized via activators regenerated by electron transfer/atom transfer radical polymerization (ARGET ATRP) utilizing functional initiators yielding molecular weights of Mn,SEC = 10900 Da, ł = 1.09 and Mn,SEC = 3900 Da, ł = 1.10, respectively. The orthogonal hydrogen bonding recognition motifs were incorporated into the polymer chain ends of the respective building blocks (to yield an eight shaped single chain folded polymers). Diblock copolymer formation was achieved via the Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction, while the single-chain folding of the prepared linear diblock copolymer-at low concentrations-was driven by orthogonal multiple hydrogen bonds via three-point thymine-diaminopyridine and six-point cyanuric acid-Hamilton wedge self-association. The self-folding process was followed by proton nuclear magnetic resonance (1H NMR) spectroscopy focused on the respective recognition pairs at low temperature. In addition, the single-chain folding of the diblock copolymer was analyzed by dynamic light scattering (DLS) and concentration dependent diffusion ordered NMR spectroscopy (DOSY) as well as atomic force microscopy (AFM), providing a limiting concentration for self-folding (in dichloromethane at ambient temperature) of close to 10 mg mL-1. © 2014 American Chemical Society