Using Microfluidic Set-Up to Determine the Adsorption Rate of Sporosarcina pasteurii Bacteria on Sandstone

Transport in Porous Media - Microbial-induced carbonate precipitation (MICP) in porous media is a two-step procedure: First, the suspension of bacteria is injected and some of the bacteria get...     

The effect of external noise in the Lorenz model of the Bénard problem

The effect of external random forces on the static and dynamic behavior of the Lorenz model is investigated. Results of a numerical calculation in the conductive, convective, and turbulent regimes are reported. The properties of static and time-dependent correlation functions of the three degrees of freedom of the model are analyzed for varying strength of the external noise level and compared with the behavior of the unforced system.     

Mixed system of Eudragit s-100 with a designed amphipathic peptide: control of interfacial elasticity by solution composition

We report an interfacially active system based on an informational peptide surfactant mixed with an oppositely charged polyelectrolyte. The 21-residue cationic peptide, AM1, has previously been shown to respond reversibly to pH and metal ions at fluid interfaces, forming elastic films that can be rapidly switched to collapse foams or emulsions on demand. Here we report the reversible association of AM1 with the methacrylate-based anionic polymer Eudragit S-100. The strength of the association, in bulk aqueous solution, is modulated by added metal ions and by ionic strength. Addition of zinc ions to the peptide-polymer system promotes complex formation and phase separation, while addition of a chelating agent reverses the association. The addition of salt weakens peptide-polymer interactions in the presence or absence of zinc. At the air-water interface, Eudragit S-100 forms an elastic mixed film with AM1 in the absence of metal, under conditions where the peptide alone does not show interfacial elasticity. When zinc is present, the elasticity of the mixed film is increased, but the rate of interfacial adsorption slows due to formation of peptide-polymer complexes in bulk solution. An understanding of these interactions can be used to identify favorable foam-forming conditions in the mixed system.     

An overview of drug screening using primary and embryonic stem cells

Cellular technologies are widely used in drug discovery to treat human diseases. Most studies involve the expression of recombinant targets in immortalized cells and measure drug interactions using simple, quantifiable responses. Such cells are also amenable to high throughput screening (HTS) methods. However, the cell phenotype employed in HTS is often determined by the assay technology available, rather than the physiological relevance of the cell background. They are, therefore, suboptimal surrogates for cells that accurately reflect human diseases. Consequently, there is growing interest in adopting primary and embryonic stem cells in drug discovery. Primary cells are already used in secondary screening assays in conjunction with confocal imaging techniques, as well as in target validation studies employing, for example, gene silencing approaches. Stem cells can be grown in unlimited quantities and can be derived from transgenic animals engineered to express disease causing proteins better coupling the molecular target with function in vivo. Human stem cells also offer unique opportunities for drug discovery in that they can be directed to specific phenotypes thus providing a framework to identify tissue-selective agents. Organizing stem cells into networks resembling those in native tissues, potentially returns drug discovery back to the highly successful pharmacological methods of the past, in which organ and tissue based systems were used, but with the advantage that they can be utilized using modern HTS technologies. This emerging area will lead to discovery of compounds whose effect in vivo is more predictable thereby increasing the efficiency of drugs that ameliorate human disease.     

Helical nanofibers of self-assembled bipolar phospholipids as template for gold nanoparticles

Bipolar phospholipids (bolalipids) represent an exciting class of amphiphilic molecules as they self-assemble in water to distinct structures of nanoscopic dimensions. Reported here are structural details of helical nanofibers, composed of achiral, symmetrical single-chain bolalipids with phosphocholine headgroups. These nanofibers are used as template for the fixation of gold nanoparticles (AuNPs) without prior functionalization. This realization of a metal array on bolalipid nanofibers is one of the rare examples of one-dimensional AuNP arrangements in solution. The loading and the heat of binding of AuNPs are determined applying transmission electron microscopy and isothermal titration calorimetry.     

Laser Writing of Block-Copolymer Images into Mesopores Using SBDC-Initiated Visible-Light-Induced Polymerization

For miniaturization, as well as for improving artificial nanopore performance, precise local polymer functionalization and the combination of different functionalities are required. Imagining data driven nanopore design automated nanopore functionalization would be beneficial. Using direct laser writing as one option of automated nanopore polymer functionalization visible light induced polymerizations are beneficial. Here, we demonstrate the functionalization of mesoporous silicafilms with two different polymers using automated laser writing. For this we developed a visible light (400–700 nm and 405 nm) N,N(diethylamino)dithiocarbamoylbenzyl(trimethoxy)silane (SBDC) inifierter initiated polymerization. While transferring this visible light induced polymerization using SBDC to a commercially available microscope, direct, automated laser writing, as well as polymer re-initiation was demonstrated. Thereby, polymer spots of 37 and 40 μm in diameter were achieved using 1–5 seconds for each irradiated spot.     

Structure-property relationship in stimulus-responsive bolaamphiphile hydrogels

The formation of temperature-, concentration-, and pH-responsive hydrogels composed of the symmetric long-chain bolaamphiphile dotriacontane-1,1'-diyl bis[[2-(dimethylammonio)ethyl]phosphate] (Me(2)PE-C32-Me(2)PE) was investigated by rheological, scattering, and spectroscopic techniques. At pH 5, this bolaamphiphile is known to form a dense network of helically structured nanofibers (K?hler et al. Soft Matter 2006, 2, 77-86). Rheological measurements and dynamic light scattering were used to describe the macroscopic behavior of the hydrogels. Small-angle neutron scattering (SANS) and time-resolved static light scattering were applied to get information about the morphology of the self-assembled aggregates. Finally, solid-state 31P NMR spectroscopy was used to gain insight into the mobility of the bolaamphiphile molecules within the fiber aggregates. In comparison with the previously examined trimethylammonio analogue PC-C32-PC, which forms temperature-dependent hydrogels, Me(2)PE-C32-Me(2)PE exhibits additional concentration- and pH-dependent gelling properties. The significantly higher stability of the Me(2)PE-C32-Me(2)PE hydrogel is supported by the SANS data, which indicate the presence of fiber aggregates up to 50 degrees C.     

General synthesis and aggregation behaviour of a series of single-chain 1,omega-bis(phosphocholines)

The synthesis and physicochemical characterisation of a series of polymethylene-1,omega-bis(phosphocholines) with even-numbered chain lengths between 22 and 32 carbon atoms is described. Two new synthetic strategies for the preparation of long-chain 1,omega-diols as hydrocarbon building blocks are presented. The temperature-dependent self-assembly of the single-chain bolaamphiphiles was investigated by cryo transmission electron microscopy (cryo-TEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR).