| 1. |
- Lundberg, Fredrik, et al.
(författare)
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Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters
- 1999
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Ingår i: Journal of Neurosurgery. - : Journal of Neurosurgery Publishing Group (JNSPG). - 0022-3085. ; 90:1, s. 101-108
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Tidskriftsartikel (refereegranskat)abstract
- Object. 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. Methods. 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. Conclusions. Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.
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| 2. |
- Montelius, Lars, et al.
(författare)
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Fabrication and characterization of a nanosensor for admittance spectroscopy of biomolecules
- 1995
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Ingår i: Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 13:3, s. 1755-1760
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated nanometer-sized interdigitated electrode patterns using electron beam lithography and liftoff techniques. The aim of the investigation was to find out whether the dimensions (i.e., the electrode separations) of the pattern would affect the admittance signal of the biomolecules in between the electrodes. Since the admittance signal scales with the geometrical factor A/d, where A is the electrode area and d is the separation, we chose to keep A/d constant when changing the electrode separation in order to eliminate this trivial effect on the admittance signal. An interdigitated electrode structure having an interelectrode spacing in the nanometer regime makes it possible to reach high nonstationary as well as stationary electric field strengths while having a low applied voltage level. Hence, electrode reactions will be as small as possible, while a high signal to noise ratio is obtained. We have been able to experimentally study the response of the impedance behavior to high electric fields exhibiting either a positive or a negative shift of the permittivity as a function of the field being a high alternating-current or a direct-current field, respectively.
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| 3. |
- Stollenwerk, Maria, et al.
(författare)
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Quantitation of bacterial adhesion to polymer surfaces by bioluminescence
- 1998
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Ingår i: Zentralblatt fur Bakteriologie. - 0934-8840. ; 287:1-2, s. 7-18
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Tidskriftsartikel (refereegranskat)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 104 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 μm → 0.3 μm, 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.
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| 4. |
- Tegenfeldt, Jonas, et al.
(författare)
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A Nanosensor for Admittance Spectroscopy
- 1995
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Ingår i: Ultimate Limits of Fabrication and Measurements. - 9789401100410 ; , s. 115-122
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Bokkapitel (refereegranskat)
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| 5. |
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| 6. |
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| 7. |
- Tegenfeldt, Jonas O., et al.
(författare)
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Image widening not only a question of tip sample convolution
- 1995
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Ingår i: Applied Physics Letters. - 0003-6951.
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Tidskriftsartikel (refereegranskat)abstract
- As the tip in the atomic force microscope is scanned over the sample surface an image results which contains information from the sample as well as from the tip. This mainly results in an increase of the apparent size of the sample. If the tip is reasonably sharp the contribution from the tip is small. In some cases the widening still persists in spite of a very sharp tip. In this letter, a model is presented which ascribes this to the lateral forces twisting the cantilever giving an offset between the apparent point of contact and the real point of contact. This results in a shift between forward and reverse scan of the sample position in the imaging window and, if the lateral forces due to the sample and substrate are different, a change in the apparent width of the sample.
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