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Tethered bilayer lipid membranes (tBLMs) have been known as stable and versatile experimental platforms for protein-membrane interaction studies. In this work, the assembly of functional tBLMs on silver substrates and the effect of the molecular chain-length of backfiller molecules on their properties were investigated. The following backfillers 3-mercapto-1-propanol (3M1P), 4-mercapto-1-butanol (4M1B), 6-mercapto-1-hexanol (6M1H), and 9-mercapto-1-nonanol (9M1N) mixed with the molecular anchor WC14 (20-tetradecyloxy-3,6,9,12,15,18,22 heptaoxahexatricontane-1-thiol) were used to form self-assembled monolayers (SAMs) on silver, which influenced a fusion of multilamellar vesicles and the formation of tBLMs. Spectroscopic analysis by SERS and RAIRS has shown that by using different-length backfiller molecules, it is possible to control WC14 anchor molecules orientation on the surface. An introduction of increasingly longer surface backfillers in the mixed SAM may be related to the increasing SAMs molecular order and more vertical orientation of WC14 at both the hydrophilic ethylenoxide segment and the hydrophobic lipid bilayer anchoring alkane chains. Since no clustering of WC14 alkane chains, which is deleterious for tBLM integrity, was observed on dry samples, the suitability of mixed-component SAMs for subsequent tBLM formation was further interrogated by electrochemical impedance spectroscopy (EIS). EIS showed the arrangement of well-insulating tBLMs if 3M1P was used as a backfiller. An increase in the length of the backfiller led to increased defectiveness of tBLMs. Despite variable defectiveness, all tBLMs responded to the pore-forming cholesterol-dependent cytolysin, vaginolysin in a manner consistent with the functional reconstitution of the toxin into phospholipid bilayer. This experiment demonstrates the biological relevance of tBLMs assembled on silver surfaces and indicates their utility as biosensing elements for the detection of pore-forming toxins in liquid samples.

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A simple approach for synthesis of palladium and silver nanostructures with readily adjustable morphologies was developed using galvanic electrochemical deposition, for application to surface-assisted laser desorption/ionization (SALDI) of small biological molecules. A range of fatty acids, triglycerides, carbohydrates, and antibiotics were investigated to assess the performance of the new materials. Intense analyte cations were generated from the galvanic surfaces upon UV laser irradiation such as potassium adducts for a film thickness <100 nm (originating from impurities of the electrolyte solution) and Pd and Ag cluster ions for films with a thickness >120 nm. Possible laser desorption/ionization mechanisms of these galvanic structures are discussed. The films exhibited self-organizing abilities and adjustable morphologies by changing electrochemical parameters. They did not require any stabilizing agents and were inexpensive and very easy to produce. SALDI analysis showed that the materials were stable under ambient conditions and analytical results with excellent measurement reproducibility and detection sensitivity similar to MALDI were obtained. Finally, we applied the galvanic surfaces to fast screening of natural oils with minimum sample preparation. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel continuum model for the impact of the sintered mesostructures on the macroscopic stress state and yield locus was found. • The specific pore surface area and fractional density are sufficient to predict the macroscopic stress state and yield locus. • Coincidence of the stress state and 43 % better prediction accuracy compared to literature is achieved. • The number of parameters is equal or smaller compared to present modelling approaches. The impact of real sintering structures on the macroscopic stress state and yield locus of sintered silver was investigated and a novel continuum modelling approach that predicts the macroscopic properties in an accurate, simple and efficient way was derived. Focused-Ion-Beam (FIB) tomography was utilized to study silver films, which were sintered under a wide range of processing conditions. With reconstructed three-dimensional representative volume elements (RVE), linear elastic and linear elastic–perfect plastic Finite-Element-Analyses were performed for a variety of loading states. The stress state ratios and the plastic yielding were investigated with respect to the mesostructural quantities obtained from the FIB tomography. The specific pore surface area and the fractional density were found to represent characteristic scalar measures for the sintering structure, which were further used to formulate a thermodynamic consistent continuum model for the macroscopic stress state and yield locus. An assessment of the modelling approach showed good coincidence of the macroscopic stress state with experiments and simulations from literature and a 43 % better prediction accuracy for the yield locus compared to established modelling approaches. The transferability of the model parameters to different silver sintering raw materials was partially proved by literature results and promises reduced parameterization effort. [ABSTRACT FROM AUTHOR]

Abstract: A mono-6-thio-β-cyclodextrin-modified silver film was synthesized via galvanic displacement on copper foil. The prepared silver films could enrich non-polar polychlorinated biphenyls (PCBs) molecules from hydrophilic phase using thiolate β-cyclodextrins (SH-β-CDs) as receptors. The components of as-prepared Ag-coated-Cu (Ag–Cu) film were confirmed by powder X-ray diffraction (XRD). Both surface-enhanced Raman spectroscopy (SERS) and energy dispersive X-ray spectroscopy (EDS) measurements gave strong evidences that the thiolated β-cyclodextrins (SH-β-CDs) had been immobilized on the surface of silver film. Compared to the substrates prepared in the absence of SH-β-CD, the surface morphology of the CD-modified Ag films was obviously changed. The interfacial enrichment and the capability of substrates to form inclusion complexes with PCBs molecules were tested by using PCB-15 (4,4′-dichlorobiphenyl) as the probe molecules via SERS technique. The measured SERS spectra could distinguish the PCB-15 molecules at micro-molar level according to the most intense CCC bending in-plane mode of PCBs. The enhancement factor (EF) of the SERS substrates for PCB-15 was 1.2×105, which was comparable with a number of previous reports. [Copyright &y& Elsevier]

We report the use of surface plasmon-coupled emission (SPCE) as an analytical tool to study the photophysics of surface-adsorbed fluorescently labeled proteins. The study uses plasma etching of PMMA surface followed by deposition of poly(diallyldimethylammonium chloride) (PDDA) for surface protein detection. PDDA increases the overall amount of the captured protein and also promotes dye aggregation. The photon-sorting properties of the SPCE process allows for wavelength separation of the individual components from the protein-dye aggregates. This has been exploited to study the fluorescence emissions from casein labeled with fluorescein isothiocyanate and concanavalin A labeled with tetramethylrhodamine. Based on the current findings, the proteins can be used to measure background fluorescence or to monitor the microenvironments in fluoroimmunoassays on SPCE substrates. [ABSTRACT FROM AUTHOR]

Metal-enhanced fluorescence (MEF) from lanthanide chelates in close proximity to silver films was studied. Different thicknesses of silver films (20 and 50 nm) were deposited onto quartz substrates using magnetron sputtering, while silver island films were prepared using a previously published procedure. Obviously enhanced emissions from the lanthanide chelates were observed on the silver films. The effect of using different concentrations of aqueous solutions polyvinyl alcohol (PVA) on MEF was also investigated. Fluorescence close to a 20-nm-thick silver film showed that the enhancement of emission is a function of the thickness of the PVA film, reaching a maximum (~2.5-fold increase in intensity) at 83 nm. In conclusion, the MEF induced by the silver films is caused by an electric field effect arising from surface plasmon resonance. [ABSTRACT FROM AUTHOR]

Abstract: Growth of silver films was studied by supercritical fluid deposition (SCFD) using H2 and acetone as reducing agents for (1,5-cyclooctadiene)(hexafluoroacetylacetonato)silver(I) in supercritical CO2 (scCO2). H2 reduction did not yield continuous Ag films, whereas continuous films were deposited on Ru substrates by acetone-assisted reduction of 0.006–0.03mol% precursor in the temperature range of 150–250°C. Surface qualities of the Ag films were effectively improved by decreasing water content in acetone reagent, as well as reducing acetone and precursor concentrations in scCO2. Ultimately, a 50nm-thick film with shiny surface was obtained in optimized conditions. A possible mechanism for acetone reduction of Ag precursor on Ru surface was also proposed. [Copyright &y& Elsevier]

Silver fluorocarboxylate tertiary phosphine complexes [Ag(O2CR)(PR'3)] (where R = CF3, C2F5, Me3SiCH2; R' = Me, Et) have been used as precursors in the hot-wall Chemical Vapour Deposition (CVD) of silver films. The pyrolysis of Ag(I) compounds and the thermal stability of metallic species transported in the gas phase were characterized by temperature variable IR (VT-IR) and MS (MS-EI) methods. Metallic films were produced between 403 and 423 K under the deposition pressure of 0.8-2.0 mbar, under an Ar atmosphere and on Si(111) substrates. They were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) integrated with EDX equipment. [ABSTRACT FROM AUTHOR]

Silver thin films (1–10 nm thick) were deposited on titanium by magnetron sputtering. We study the effect of the current (20–65 mA) and the argon pressure (5–20 mtorr) on the films morphology. Their structure is characterized by electron spectroscopy for chemical analysis (ESCA) and atomic force microscopy (AFM). The ESCA data are analysed by means of the quases™ code. The data are fitted by means of a model in which the surface is assumed to be composed of two kinds of features: islands and a thin layer. It is shown that the islands coverage coefficient may attain 95%. The films are also characterized by AFM. It appears that the surface roughness is important, due to the roughness of the initial Ti film. A comparison of the AFM and quases™ results shows that the structure is such that clusters of Ti are covered by a thin layer of Ag. The space between Ti clusters is filled with clusters of Ag. The coverage and the thickness of the films depend on the deposition rate and the total argon pressure. [Copyright &y& Elsevier]

In this work, the assembly of functional tethered bilayer membranes (tBLMs) on silver surface was demonstrated for the first time. To avoid degradation of thin silver films the non-corrosive mixture of thiols composed of WC14 molecular anchor and 3-mercapto-1-propanol (3M1P) serving as a backfiller was used to self-assemble monolayers which allowed fusion of multilamellar vesicles and tBLM formation. tBLMs on silver films exhibited high stability and low residual defect densities as measured by the electrochemical impedance spectroscopy (EIS). Silver supported tBLMs demonstrated all features typical for interactions of pore-forming proteins and bilayer membranes. Specifically, the EIS spectral response was typical for the formation of water filled defects when tBLMs were exposed to the solution of vaginolysin (VLY), the cholesterol dependent cytolysin. Increase of defect density was observed only in case tBLMs contained significant amount, e.g., 50 %, of cholesterol, thus confirming functional reconstitution of vaginolysin into tBLMs. This observation is consistent with the biological nature of interaction between the bilayer and the cholesterol dependent cytolysins. The reconstitution of VLY was confirmed by the direct imaging of the protein entities in tBLMs by the atomic force microscopy (AFM). Notably, the quantitative estimate of the functional protein-pores in tBLMs measured by EIS, was found to be close to the number of VLY entities in tBLMs measured by the AFM. Our work demonstrates that silver can serve as less expensive alternative to gold in designing tBLM based devices, for example phospholipid biosensors, as well as the experimental platform for studying membrane protein interactions by electrochemical, and microscopy techniques. [ABSTRACT FROM AUTHOR]