A simple strategy based on photobiotin irradiation for the photoelectrochemical immobilization of proteins on electrode surfaces

A photoactivable organic polymer was prepared first by electrogeneration of a conductive biotinylated polypyrrole film in acetonitrile electrolyte. The successive anchoring of avidin and photobiotin led to a multilayer configuration. The latter was illuminated with light (wavelength 370–400 nm) in the presence of proteins adsorbed onto its surface. The irradiation allowed the covalent linking of the proteins to the modified electrode. As a result of the photochemical reaction, a monolayer of enzyme (glucose oxidase, GOX or alkaline phosphatase, AP) was covalently bound to the photobiotin-modified surface with retention of their catalytic activities. The surfacic activities were 34 and 1.69 mU cm^− 2 for GOX and AP photobiotin electrodes, respectively. These enzyme electrodes were compared to similar configurations obtained through the immobilization of biotinylated glucose oxidase or avidin-conjugated alkaline phosphatase on biotinylated polypyrrole film. Our results suggest that both procedures led to the immobilization of the same enzyme amount, namely a protein monolayer. This novel photo-immobilization methodology was also successfully applied to the anchoring of an anti-cholera toxin antibody which was then detected by a secondary antibody labelled with a peroxidase.     

CE-Bézier曲面光滑拼接的研究与实现

针对CE-Bézier曲面造型中复杂曲面难以用单一曲面来表示的问题,通过分析CE-Bézier曲线的唯一性,提出了一种新的CE-Bézier曲面的光滑拼接技术。首先,在分析第1类CE-Bézier曲线基函数及其端点性质的基础上,对第1类CE-Bézier曲线的唯一性进行了研究,得出了对于同一条第1类CE-Bézier曲线可以有很多组不相同的控制顶点和形状参数与之对应的结论;其次,利用该结论进一步给出了两相邻第1类CE-Bézier曲面片间G1光滑拼接的一般几何条件,并通过合理地选取形状参数,进一步简化了该曲面的G1拼接条件;最后,给出了第1类CE-Bézier曲面光滑拼接的几何造型实例。实例结果表明,该方法简单、直观、易实现,有效地增强了CE-Bézier方法表达复杂曲线曲面的能力,可广泛地应用于工程复杂曲面的造型系统中。     

Absorption mapping for characterization of glass surfaces

The surface quality of bare substrates and preparation procedures take on an important role in optical coating performances. The most commonly used techniques of characterization generally give information about roughness and local defects. A photothermal deflection technique is used for mapping surface absorption of fused-silica and glass substrates. We show that absorption mapping gives specific information on surface contamination of bare substrates. We present experimental results concerning substrates prepared by different cleaning and polishing techniques. We show that highly polished surfaces lead to the lowest values of residual surface absorption. Moreover the cleaning behavior of surfaces of multicomponent glasses and their optical performance in terms of absorption are proved to be different from those of fused silica.     

A factorial analysis of automatic transfer line systems

A 2³ factorial experiment was conducted based on a discrete-time computer model to elucidate the effects of system configuration, relative stage position and buffer capacity allocation in automatic transfer line systems under steady-state conditions. A total of 96 simulated experiments were conducted. It was found that second and third-order interaction effects could be statistically significant, a potentially useful result being the possibility of increasing production rate and decreasing average in-process stock simultaneously     

Probabilistic failure analysis for real glass components under general loading conditions

In this paper, the generalized local model (GLM) is applied to derive the primary failure cumulative distribution function (PFCDF) of annealed glass in order to achieve the failure prediction of structural glass. The uniqueness of the glass characterization is demonstrated irrespective of the test, specimen size, and geometry used. Consequently, the strength of glass is unequivocally derived in a probabilistic way as a material property, so that the definition of normalized testing specimens in international standards might be put under question. Furthermore, the application of the GLM to the results assessment allows to ensure a correct transferability of the laboratory data from simple specimens to the practical design of real glass components and vice versa. The feasibility of the GLM to characterize the strength of annealed glass from different test types is illustrated by means of an extensive experimental program.     

Enhanced processing of coatings on glass surfaces

In this contribution, basic technically usable interactions of atmospheric pressure plasmas (APP), laser irradiation and solids as well as a technique which combines such plasmas and laser irradiation are introduced. Two examples for plasma‐enhanced laser processing of coatings on glass surfaces are presented in more detail. First, APP‐assisted annealing of amorphous silicon layers is discussed. It is shown that the crystallised area is notably increased by assisting plasmas where the particular improvement factor depends on the particularly applied type of plasma. Second, the impact of assisting plasmas on laser removal of lacquers and varnishes from glass surfaces is presented. By introducing a plasma jet to the laser removal process, the laser energy required for cleaning or delamination is notably reduced.     

Morphological relaxation of glass surfaces

A model for calculating the morphological relaxation of two-dimensional glass profiles for arbitrary temperature-time schedules is described. The model is based on a Fourier expansion of the surface profile for which the decay with time can easily be calculated for each of the separate terms. The effect of the variable temperature with time was accounted for by discretization of the temperature-time profile. Necessary input data are the viscosity and surface tension of the glass. The sensitivity to various geometrical details is limited, but heating/cooling effects appeared to be important. The predictions of the model are verified by measurements on glass samples with various profiles and relaxed according to a certain temperature-time schedule. Using a surface tension value of 0.19 N m^–1, as determined with recent fibre-on-plate experiments, excellent agreement between theory and experiment was obtained. Possible options for extension to threedimensional profiles are indicated.     

Controlling binding site densities on glass surfaces

The density of surface-immobilized ligands or binding sites is an important issue for the development of sensors, array- or chip-based assays, and single-molecule detection methods. The goal of this research is to control the binding site density of reactive ligands on surfaces by diluting surface amine groups in self-assembled and cross-linked monolayers on glass prepared from solutions containing very low concentrations of (3-aminopropyl)triethoxysilane (APTES) and much higher concentrations of (2-cyanoethyl)triethoxysilane. The surface amine sites are suitable for attaching labels and ligands by reaction with succinimidyl ester reagents. Labeling the amine sites with fluorescent molecules and imaging the single molecules with fluorescence microscopy provides a means of determining the density of amine sites on the surface, which were incorporated into the self-assembled monolayer with micrometer spacings in proportion to the concentration of APTES in the synthesis. Biotin ligands were also bound to these surface amine sites using a succinimidyl ester linker, and the immobilized biotin was then reacted with either streptavidin-conjugated gold colloid particles or fluorescently labeled neutravidin. Imaging of these samples yields consistent amine and biotin site coverages, indicating that quantitative control and chemical conversion of binding sites can be achieved at very low (<10(-7)) fractions of a monolayer.     

Radiation effects on lead silicate glass surfaces

Radiation-induced changes in the microstructure of lead silicate glass were investigated in situ under Mg K irradiation in an ultra-high vacuum (UHV) environment by X-ray photoelectron spectroscopy (XPS). Lead-oxygen bond breaking resulting in the formation of pure lead was observed. The segregation, growth kinetics and the structural relaxation of the lead, with corresponding changes in the oxygen and silicon on the glass surfaces were studied by measuring the time-dependent changes in concentration, binding energy shifts, and the full width at half maximum. A bimodal distribution of the oxygen XPS signal, caused by bridging and non-bridging oxygens, was found during the relaxation process. All experimental data indicate a reduction of the oxygen concentration, a phase separation of the lead from the glass matrix, and the metallization of the lead occurred during and after the X-ray irradiation.     

Impact of small steel spheres on glass surfaces

A high speed photographic study has been made as part of a detailed investigation of the impact of small steel spheres ( 800 and 1000 m diameter) on to Pyrex and soda-lime glasses. The velocity of the spheres was varied from 20 to 300 m sec^–1 and the fracturing process during the complete impact cycle was followed. Observations revealed substantial differences in the behaviour of the two glasses, particularly at higher velocities; Pyrex behaved as though indented by a sphere, whereas soda lime glass behaved as though indented with a pointed indenter. As with quasi-static pointed indentations, cracking was observed during the unloading cycle. It was also found that the angle of the Hertzian cone crack in Pyrex glass varied in a systematic manner with velocity. Rebound velocity, time of contact and extent of flattening of the steel spheres were also recorded. The relevance of these observations to impact erosion and strength degradation of brittle materials is pointed out.     

Investigation of surface roughness on etched glass surfaces

Roughening the surface of solar cells is a common practice within the photovoltaic industry as it reduces reflectance, and thus enhances the performance of devices. In this work the relationship between reflectance characterized by the haze parameter, surface roughness and optical properties was investigated. To achieve this goal, model samples were prepared by hydrofluoric acid etching of glass for various times and measured by optical microscopy, spectroscopic ellipsometry, scanning electron microscopy, and atomic force microscopy. Our investigation showed that the surface reflectance was decreased not only by the roughening of the surface but also by the modification of the depth profile and lowering of the refractive index of the surface domain of the samples.     

Silver nanoparticles preferentially reduced on PEG-grafted glass surfaces for SERS applications

Silver nanomaterials have been extensively investigated due to their unique optical and biological properties. Surface plasmons and scattering phenomena occurring on silver nanostructures can provide useful analytical or sensor platform. Here, we present silver nanoparticles preferentially reduced on polyethylene glycol (PEG)-grafted glass surfaces for application to surface-enhanced Raman scattering (SERS). Uniform silver nanoparticles of ∼50 nm size were easily generated by dipping the PEG-grafted glass surfaces in silver salt solution at room temperature without any additional reducing agent. The silver nanoparticles generated on the PEG-grafted surfaces were confirmed by AFM and FE-SEM analysis.     

Argon plasma treatment of glass surfaces

The effect of argon plasma treatment of glass surfaces is studied by FTIR and SEM. The argon plasma on cleaned glass surfaces resulted in increased surface area due to microetching and surface rearrangement of the silicate network as indicated by the observed changes in the Si-O stretching infrared absorption. The result was a relative increase in surface hydrophilicity which could be optimized by the plasma reaction conditions. The etching action of the argon plasma on the substrate surfaces facilitated the removal of the micrometre thick sizing from the commercial fibres accompanied by little loss in tensile strength. Plasma was also used to graft selected monomers to the surface of glass fibres for enhancement of bond compatibility in a composite system. This grafting treatment was followed by an argon etching step. The argon plasma action on the coated surfaces improved the wettability further and increased the sur face area. Changes in surface chemistry that accompanied the argon etching treatment were very subtle in the case of the plasma polymer of allylamine, but proved significant in the case of the plasma polymer of hexamethyldisiloxane. On the latter surfaces, rearrangement of the siloxane (Si-O-Si) bonds to silylmethylene (Si-(CH₂) _n -Si) groups is suggested.     

A perturbation analysis on solid polymer surfaces

A linear stability model was formulated to analyze the perturbation of solid polymer surfaces. Surface energy and thermal stress were considered as the main variables. The surface tends to more unstable as the temperature increase. This is interpreted as the dominancy of the lattice vacancy diffusion over surface mass diffusion and the increase in thermal stress.     

Dextran‐based coating system for the immobilization of cell adhesion promoting molecules on titanium surfaces

Immobilization of adhesive peptides interacting with cellular integrin receptors onto metallic implant surfaces represents a promising approach to improve osseointegration of implants into the surrounding tissue. In the present study, a functional dextran‐based coating system consisting of an amino titanate adhesion promoter with dendritic structure and a carboxymethyl dextran was established to bind an RGD‐containing adhesive peptide via a selective coupling methodology onto titanium surfaces. The three‐step reaction procedure was characterized by X‐ray photoelectron spectroscopy. In cell adhesion experiments it could be demonstrated that dextran coatings containing immobilized RGD promote attachment and spreading of fibroblast and pre‐osteoblastic cells compared to native as well as CMD‐coated titanium surfaces without RGD. The direct attachment of the RGD sequence to the metal surface via the amino titanate adhesion promoter did not increase pre‐osteoblastic cell spreading, whereas coupling of RGD to the polymeric carboxy­methyl dextran layer slightly enhanced spreading of the cells.     

Orientation-defined alignment and immobilization of DNA between specific surfaces

DNA-based single-molecule studies, nanoelectronics and nanocargos require a precise placement of DNA in an orientation-defined manner. Until now, there is a lack of orientation-defined alignment and immobilization of DNA over distances smaller than several micrometers. However, this can be realized by designing bifunctionalized DNA with thiol at one end and (3-aminopropyl) tri-ethoxy silane at the other end, which specifically binds to a gold and SiO? layer after and during alignment, respectively. The electrode assembly consists of platinum as the electrode material for applying the AC voltage and islands of gold and silicon dioxide fabricated at a distance of about 500-800 nm by electron-beam lithography. The orientation-defined alignment and covalent binding of pUC19 DNA to specific surfaces are carried out in frequency ranges of 50 Hz-1 kHz and 100 kHz-1 MHz and observed after metallization of DNA by palladium ions by field emission scanning electron microscopy (FESEM). The bifunctionalized 890 nm long DNA was effectively aligned and immobilized between a gap of 500 to 600 nm width.     

Electrochemical control of bacterial cell accumulation on submerged glass surfaces

 Accumulation of bacterial cells on a transparent electrode was controlled by applying an alternating potential. Live and dead cells on a transparent electrode can be distinguished as blue and red cells, by staining with two fluorescent dyes, propidium iodide (PI) and 4′, 6-diamidino-   2-phenylindole dihydrochloride (DAPI) and propidium iodide (PI), respectively. Cells of the gram-negative marine bacterium, Vibrio alginolyticus attached to an indium/tin oxide (ITO) electrode were killed by applying a potential of 1.1 V versus saturated calomel electrode in seawater. By applying –0.4 V, 73% of the cells on the ITO electrode were desorbed in 10 min. Changes in pH and generation of chlorine were not observed after applying potentials in the range of –0.4∼1.2 V. After 21 h of immersion in V. alginolyticus cell suspension with the application of an alternating potential of 1.1 and –0.4 V, cells on the electrode were completely killed and the cell number decreased to 20% of that of no potential. Elution of indium and tin was not observed after 10 days application of alternating potential. Received: 11 August 1998 / Accepted: 30 September 1998     

Stepwise functionalization of SiNx surfaces for covalent immobilization of antibodies

A stepwise functionalization of silicon nitride surfaces is followed by X-ray photoelectron spectroscopy (XPS). The first step involves a silanization reaction leading to the formation of a silane film with a thickness estimated by XPS of one or two molecular layers. A monoprotected homobifunctionalized linker is then used to avoid the formation of bridge structures on the surface. The linker reacts quantitatively with the amino groups of the surface as outlined by the absence of residual unreacted CNH₂/CNH₃⁺ groups in XPS analyses. Deprotection of the ester groups of the immobilized linker and subsequent reaction with N-hydroxysuccinimid lead to N-hydroxysuccinimid activated surfaces able to react with biological species. These surfaces were then incubated with anti-transferrin antibodies. As seen by XPS and atomic force microscopy analyses, the concentration and incubation conditions of antibodies are important to obtain a compact layer of antibodies on the surface. All chemical steps of the procedure are compatible with microelectronic process on silicon. Moreover, antibodies introduced under native conditions at physiological pH, in the last step of the immobilization process, recognized specifically antigens, as shown by fluorescence competitive assay.     

Selection of drilling conditions for glass fibre reinforced plastics

An experimental investigation has been carried out into the drilling of glass fibre reinforced plastics using HSS twist drills. A test series was conducted using a wide range of cutting conditions and drill geometry, namely cutting speed, feed rate, point angle and helix angle. Decisions relating to the ‘optimum’ drilling conditions were based on the geometrical accuracy and appearance of the produced holes. Drill wear was measured during the test trials and used as a further constraint in ‘optimum’ cutting conditions selection. Speed, feed rate and drill point angle were found statistically to be the most significant parameters influencing hole quality. Drill wear can be successfully correlated to the level of the thrust force. A simple nomogram is included to predict drill wear level from the thrust level or the amount of material removed.