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ABSTRACT: Here, we review the use of actin-based motors, (myosins; e.g., the molecular motor of muscle) in nanotechnology. The review starts from the viewpoints of the molecular motors as being important devices responsible of cargo transportation in the cell and end in discussions about their employment in nanotechnological applications. First, we describe basic biophysics of the myosin motors with focus on their involvement in cargo transportation in the living cell, leading us over into a discussion about in vitro motility assays. These are biological test systems where the myosin-induced translocation of actin filaments is studied on an artificial surface outside the cell. Then follows a review about modified motility assays for production of ordered motion. Here, we discuss ours and others' work with regards to making micro- and nanostructured surfaces and channels where the position and direction of movement produced by molecular motors is controlled. In this section, we consider the role of the channel size in promoting unidirectional myosin-induced motion of actin filaments. Furthermore, we consider the usefulness of surface modifications, e.g., various silanization procedures in order to promote and hinder molecular motility, respectively. Particularly, we describe our latest test system being both morphologically and chemically nanostructured giving us unsurpassed possibilities to perform functional studies as well as extremely good spatio-temporal control. Then follows a section about nanotechnological cargo transportation systems based on the actomyosin motor system. For instance, we present results of attaching fluorescent quantum dots as cargoes to the actin filaments. In this section, we also discuss the possibilities of having cargo attachment and detachment being performed on demand. Finally, we consider the usefulness of molecular motors for lab-on-a-chip applications and the requirements for incorporating these motors in commercially viable devices. In this context, the significant potential of the actomyosin motor system to overcome traditional limitations of micro- and nanofluidics is stressed.
IEEE Transactions on Advanced Packaging 12/2005; · 1.12 Impact Factor
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ABSTRACT: The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF--fibronectin, vitronectin, and fibrinogen--are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined.
The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts.
Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.
Journal of Neurosurgery 02/1999; 90(1):101-8. · 2.96 Impact Factor
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ABSTRACT: Quantitation of microbes adhering to a surface is commonly used in studies of microbial adhesion to different surfaces. We have quantified different staphylococcal strains adhering to polymer surfaces by measuring bacterial ATP (adenosine triphosphate) by bioluminescence. The method is sensitive, having a detection limit of 10(4) bacterial cells. Viable counting of bacterial cells may yield falsely low results due to the presence of "dormant" and adherent bacteria. By using bioluminescence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantly in their basal ATP content (8.7 x 10(-13) - 5.2 x 10(-22) MATP). The size of adherent and planktonic bacteria decreased with time (0.7 micron-->0.3 micron, 20 days). During incubation in nutrient-poor buffer ("starvation"), the ATP content of adherent bacteria decreased after 24-96 h whereas that of planktonic bacteria was stable over 20 days. The presence of human serum or plasma did not interfere significantly with the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth conditions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the same culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.
Zentralblatt für Bakteriologie: international journal of medical microbiology 01/1998; 287(1-2):7-18.
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ABSTRACT: Biomaterials are commonly used in modern medicine. Proteins are adsorbed to the surface of the biomaterial immediately after insertion. This report demonstrates the presence of adsorbed proteins in one infected cerebrospinal shunt from a child with hydrocephalus and on fifteen temporary ventricular catheters from adult patients with spontaneous or traumatic brain injuries. Depositions of vitronectin, fibrinogen and thrombospondin-fibronectin to some extent--on the shunt surface was imaged by field-emission scanning electron microscopy. Vitronectin, fibronectin, fibrinogen, and thrombospondin on the ventricular catheters were shown with radio-actively labelled antibodies. Furthermore, protein adsorption from human cerebrospinal fluid to heparinized and unheparinized polymers was studied under flowing conditions in vitro. On heparinized polymer, significantly reduced levels of vitronectin, fibronectin, and thrombospondin were exposed, as measured after 4 hours in vitro perfusion. After 24 hours perfusion, the differences in protein exposition between heparinized and unheparinized polymers were substantially reduced.
Acta Neurochirurgica 02/1997; 139(8):734-42. · 1.52 Impact Factor
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ABSTRACT: It is a well‐known fact in scanning probe microscopy that the tip geometry will be convoluted with the shape of the sample. In this study we report on a clear‐cut in situ direct observation of the real shape of the atomic force microscopy (AFM) tip using the AFM technique itself, utilizing a specially designed sample. The sample was an array of columns fabricated using aerosol deposition of metal particles and subsequent plasma etching. In this article we report on the so‐called inverse AFM mode in which the tip is actually used as the sample and vice versa. We will present results using ordinary AFM tips and ‘‘tapping‐mode’’ tips as well as high‐aspect‐ratio supertips (Nanoprobe). We propose how this method can, with a very high accuracy, be used for studying objects, e.g., biomolecules, that are deliberately attached to the usual AFM cantilever tip. Finally, we discuss how this method can significantly increase the reliability of the obtained AFM images.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 06/1994; · 1.34 Impact Factor
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ABSTRACT: In this study we report on the first direct observation of the real shape of the atomic force microscopy (AFM) tip using the AFM technique itself, utilizing a specially designed sample geometry. This is the first report of the so‐called inverse AFM mode in which the tip is actually used as the sample and vice versa. We propose how this method can, with a very high accuracy, be used for studying objects, e.g., biomolecules, that are attached to the usual AFM cantilever tip. Finally, we discuss how this method can significantly increase the reliability of the obtained AFM images.
Applied Physics Letters 06/1993; · 3.84 Impact Factor
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ABSTRACT: The interest in miniaturization of modern chemical and medical sensors is steadily increasing. However, when employing methods and fabrication procedures especially developed for microelectronics, one may encounter new and unpredictable problems for applications in aqueous media. For instance, in microelectronics often a dual metal layer system is employed for making electrical contacts. In a solution such a contact may result in galvanic reactions and/or may dissolve in the cleaning agents used for sterilization of medical devices. To address such issues the authors have employed an all-silicon based process technology for fabrication of sturdy and reliable devices with integrated poly-Silicon electrodes that tolerate most chemical environments. In this presentation the authors report on the first results using such electrodes. A comparative study between identical poly-Si and Aluminium electrodes was made in order to investigate the usefulness of poly-Si electrodes. The authors also demonstrate the nice possibility to use well-documented methods for surface modifications using silane coupling chemistry. The authors believe this added benefit for the silicon based electrodes of easy surface modification processes, as compared with metal electrodes, to be extremely valuable for the development of accurate and tailored sensor structures for specific applications
Engineering in Medicine and Biology Society, 1996. Bridging Disciplines for Biomedicine. Proceedings of the 18th Annual International Conference of the IEEE;
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ABSTRACT: In the microelectronics industry, gold electrodes on silicon dioxide are produced using an adhesive layer of chromium or titanium. This method is applicable whenever a dry environment is present. However, when such an electrode is exposed to an electrolyte a galvanic cell is formed and the less noble metal will dissolve and eventually destroy the electrode. We describe here how a monolayer of mercaptopropyl-trimethoxysilane (MPTS) can be used as an adhesive. The layer can be structured lithographically making gold electrodes in the micro- and nano-range applicable for use in electrochemistry. The properties of the MPTS layer were investigated with photoelectron microscopy, atomic force microscopy and the electrochemical performance of the gold electrodes was determined by cyclic voltammetry.
Microelectronic Engineering · 1.56 Impact Factor
