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Nanobiotechnology, IEE Proceedings -

Issue 3 • Date 4 June 2004

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Displaying Results 1 - 10 of 10
  • Functionalisation of surfaces with S-layers

    Page(s): 83 - 86
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (487 KB)  

    Two-dimensional bacterial surface layer protein crystals (S-layers) are the most commonly observed cell surface structures in prokaryotic organisms (bacteria and archaea). Isolated S-layer proteins have the intrinsic tendency to self-assemble into two-dimensional arrays in suspension and at various interfaces. Basic research on the structure, genetics, chemistry, morphogenesis and function of S-layers has led to a broad spectrum of applications in molecular nanotechnology and biomimetics. The possibility to change the natural properties of S-layer proteins by genetic manipulation opens new ways for the tuning of their structural and functional features. Functionalised S-layer proteins that maintain their propensity for self-assembly have led to new affinity matrices, diagnostic tools, vaccines or biocompatible surfaces, as well as to biological templating or specific biomineralisation strategies at surfaces. View full abstract»

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  • Ellipsometric microscopy: developments towards biophysics

    Page(s): 95 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    Ellipsometric microscopy is a novel technique that combines the merits of ellipsometry and light microscopy, i.e. it allows noninvasive, label-free measurements of thin film thickness and refractive index at high lateral resolution. Ellipsometric microscopy has been successfully applied to silicon-air interfaces. However, typical biological systems require immersion in an aqueous buffer. Thus the authors have adapted the instrument for the observation of the interface between glass and water. In particular, the comparatively small differences in refractive indices between substrate and ambient media proved to be a challenge for instrument design. The first experiments with this new instrument are presented. View full abstract»

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  • Patterning to enhance activity of cultured neuronal networks

    Page(s): 109 - 115
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1793 KB)  

    Embryonic rat hippocampal neurons were cultured in order to gain insights into how small networks of neurons interact. The principal observations are the electrical activities recorded with the electrode arrays, primarily action potentials both spontaneous and evoked. Several lithographic techniques were developed for controlling with micrometer precision the patterns of surface molecules in order to control neuronal attachment and growth. Cytophilic polylysine against protein repellent and hence cytophobic polyethylene glycol were used. By combining the cellular lithography with the microelectrode arrays it was possible to guide neurons preferentially to electrodes and to begin to investigate the question as to whether the geometric pattern of a neuronal network influences the patterns of its neuroelectric activity. It is clear that the techniques are adequate to ensure contact of neurons to electrodes but not to ensure the recording of signals, even when neurons lie directly on top of electrodes. The maturation of neuroelectric activity depends on the growth of glia within the culture, such that spontaneous activity appears to become robust when the number of glia is roughly the same as the number of neurons. View full abstract»

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  • Analysis of electrotonic coupling in patterned neuronal networks

    Page(s): 122 - 127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    Microcontact printing of laminin is known as an efficient approach for guiding neuronal cell migration and neurite outgrowth on artificial surfaces. In the present study, ultrathin (∼250 μm) brain stem slices of Sprague-Dawley rats (E15-E18) were cultured on laminin-patterned substrates such that neuronal cells migrating out of the slices formed grid-shaped neuronal networks along the geometry defined by the pattern. The interconnections between neighbouring pairs of neurons within these artificial networks were assessed electrophysiologically by double patch-clamp recordings and optically by microinjection of fluorescent dyes. Both functional and electrotonic synapses were detected. Based on the recorded data and simulations in PSpice, an electrical model for electrotonically coupled cells was derived. In this model the neuritic pathway is described as a cylindric cable and gap junctions are represented by an ohmic resistor. Applying this model in the data analysis the average inner radius of neurites could be determined to be ∼0.1 μm. In addition, evidence was found for a correlation between the pathwidth of the applied pattern and the diameter of neurites growing along these paths. View full abstract»

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  • Osteoblast cell membrane hybrid bilayers for studying cell-cell interactions

    Page(s): 75 - 81
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (903 KB)  

    Osteoblast-like cells were grown on a surface that presents cell membrane components to the cells in culture. The culture surface was a bimolecular layer formed by the interaction of osteoblast plasma membrane vesicles with an alkanethiol monolayer. The potential of these osteoblast-membrane hybrid bilayers for promoting osteoblast adhesion, growth and differentiation was examined. UMR-106 osteoblast-like cells cultured on these surfaces are normal in appearance, and in the presence of serum, proliferate as well or better than on control surfaces. The level of alkaline phosphatase production in the presence and absence of serum suggests that the osteoblast-like cells retain their differentiated phenotype, and appear to respond to the cell surface ligands presented by the osteoblast-membrane biomimetic surface. These observations suggest that biomimetic membrane films prepared from osteoblast cell membranes support osteoblast cell growth, allow the cells to maintain their differentiation state and may be suitable as a model system to probe cell-cell interactions. View full abstract»

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  • Biomolecule-compatible support structures for biomolecule coupling to physical measuring principle surfaces

    Page(s): 87 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    As part of studies on biomolecule-compatible interfacial structures for practice-relevant biosensor and biochip developments, new film-forming aminocelluloses of the 'P-CH2-NH-(X)-NH2' type (P=cellulose) with spacer structures (X=special oligoamine residues) at C6 and solubilising groups (S=tosylate or carbanilate) at C2/C3 of the anhydroglucose unit (AGU) were synthesised and their film properties and covalent coupling with enzyme protein examined. Depending on the nature and degree of substitution (DS(S)) of the ester groups (S) at C2/C3, the new aminocellulose derivatives are soluble either in DMA and DMSO (with S=carbanilate) or in water (with S=tosylate). The aminocellulose derivatives form transparent films from their solutions. AFM investigations of the film surfaces have either shown very flat (topography <1 nm) films or tubular topographies of nanostructure size, depending on structural and environment-induced factors of influence. Especially in the case of films from water-soluble aminocelluloses with oligoamine residues at C6, inter alia, enzyme-specific pH values and different positive charge distributions can be adjusted by partial protonation of the NH2 end groups. By means of the covalent coupling of the new aminocelluloses with glucose oxidase (GOD) it was shown that the enzyme coupling efficiency can be decisively optimised by the interplay of aminocellulose structure, coupling structure and enzyme protein. View full abstract»

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  • Pattern modification of a neuronal network for individual-cell-based electrophysiological measurement using photothermal etching of an agarose architecture with a multielectrode array

    Page(s): 116 - 121
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (599 KB)  

    A new type of individual-cell-based on-chip multielectrode array (MEA) cell-cultivation system with an agarose microchamber (AMC) array for topographical control of the network patterns of a living neuronal network has been developed. The advantages of this system are that it allows control of the cell positions and numbers for cultivation using AMCs, as well as easy and flexible control of the pattern of connections between the AMCs through photothermal etching where a portion of the agarose layer is melted with a 1480 nm infrared laser beam. With adequate laser power, narrow micrometer-order grooves (microchannels) can easily be fabricated that can be used to combine neighbouring AMCs to enable topographical control of the neural network pattern. Using this system, an individual-cell-based neural network pattern was formed of rat hippocampal cells within the AMC array without cells escaping from the electrode positions in the microchamber during an eight-day cultivation, and could record cell firing in response to 1.5 V, 500 kHz stimulation through an electrode. This demonstrated the potential of the on-chip AMC/MEA cell cultivation system for long-term single-cell-based electrophysiological measurement of a neural network system. View full abstract»

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  • Self-assembling of proteins and enzymes at nanoscale for biodevice applications

    Page(s): 101 - 108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (901 KB)  

    Different nanotechnological strategies have been selected to implement biomolecular devices following a bottom-up or top-down approach depending on the biomolecule and on its functionality. Biomolecules have particular functionality and self-assembling capabilities that can be exploited for the implementation of both bioelectronic devices and multipurpose engineered biosurfaces. Surface preparation with supramolecular methods and microcontact printing have been developed and optimised to realise suitable functionalised surfaces. These surfaces can be used to link metalloproteins and enzymes for the implementation of nanobioelectronic devices and planar biosensors or to bind cells in order to promote their growth along predefined tracks and grooves. Some possible applications of these biosurfaces are shown and discussed. Results are presented for the realisation of a biomolecular nanodevice working in air based on the metalloprotein azurin immobilised in the solid state, the formation and characterisation of functional glutamate Dehydrogenase monolayers for nanobiosensing applications, the results of soft lithography processes on azurin for biosensor implementation, and the development of physiological self-assembled patterns of laminin-1 for cell culture applications and hybrid devices. View full abstract»

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  • Molecular resolution of cell adhesion forces

    Page(s): 128 - 132
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (659 KB)  

    Recently, AFM-based force spectroscopy has been used to quantify single-molecule adhesion forces on living ameboid cells. Force spectroscopy was used to measure the rupture forces of single receptor-ligand bonds which can occur rapidly between the cell types used, a metastasising B16 melanoma cell and a vascular bEnd.3 endothelial cell. Parameters which influence the critical experimental conditions are discussed to discriminate between multiple bond ruptures and single bonds. Under physiological conditions of temperature and pH the force measurements show an average rupture force of 33 pN (SD=12 pN) for single bonds. Single-molecule force spectroscopy will be very useful to study the regulation of cell adhesion on a molecular level in normal processes, such as leukocyte homing, and in major human disorders, including tumor metastasis, autoimmune diseases and atherosclerosis. View full abstract»

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