| 1. |
- Deschout, Hendrik, et al.
(författare)
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Straightforward FRAP for quantitative diffusion measurements with a laser scanning microscope
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:22, s. 22886-22905
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Tidskriftsartikel (refereegranskat)abstract
- Confocal or multi-photon laser scanning microscopes are convenient tools to perform FRAP diffusion measurements. Despite its popularity, accurate FRAP remains often challenging since current methods are either limited to relatively large bleach regions or can be complicated for non-specialists. In order to bring reliable quantitative FRAP measurements to the broad community of laser scanning microscopy users, here we have revised FRAP theory and present a new pixel based FRAP method relying on the photo bleaching of rectangular regions of any size and aspect ratio. The method allows for fast and straightforward quantitative diffusion measurements due to a closed–form expression for the recovery process utilizing all available spatial and temporal data. After a detailed validation, its versatility is demonstrated by diffusion studies in heterogeneous biopolymer mixtures.
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| 2. |
- Henfridsson, Ola, 1970, et al.
(författare)
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User Involvement In Developing Mobile and Temporarily Interconnected Systems.
- 2010
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Ingår i: Information Systems Journal. - : Wiley-Blackwell Publishing Ltd.. - 1350-1917 .- 1365-2575. ; 20:2, s. 119-135
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Tidskriftsartikel (refereegranskat)abstract
- Information systems (IS) research on user involvement has primarily theorized relationships between developers, managers and users in systems development. However, so far, marginal attention has been paid to differences in user involvement practices between information systems. This paper explores user involvement in developing mobile and temporarily interconnected systems (MTIS). We refer to MTIS as heterogeneous systems that rely on network technologies for increasing the ubiquity of information services for users on the move. Such systems are becoming increasingly important in leveraging, e.g. car infotainment, supply chain management and wireless e-commerce. With particular emphasis on the nature of MTIS and its implications for user involvement, the paper analyses the systems development process of an action research project. The findings suggest that user involvement practices need to be adapted to accommodate features of this class of systems. Being an early attempt to trace the implications of technology features such as use context switches and temporary system relationships, the paper contributes to the development of an updated theory of the user role in an era of increased system complexity and stakeholder ambiguity.
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| 3. |
- Jonasson, Jenny, 1976, et al.
(författare)
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Pixel-based analysis of FRAP data with a general initial bleaching profile
- 2010
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 239:2, s. 142-153
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Tidskriftsartikel (refereegranskat)abstract
- Jonasson et al. (2008), we presented a new pixel-based maximum likelihood framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM). The main method there, called the Gaussian profile method below, is based on the assumption that the initial intensity profile after photobleaching is approximately Gaussian. In the present paper, we introduce a method, called the Monotone profile method, where the maximum likelihood framework is extended to a general initial bleaching profile only assuming that the profile is a non-decreasing function of the distance to the bleaching centre. The statistical distribution of the image noise is further assumed to be Poisson instead of normal, which should be a more realistic description of the noise in the detector. The new Monotone profile method and the Gaussian profile method are applied to FRAP data on swelling of super absorbent polymers (SAP) in water with a Fluorescein probe. The initial bleaching profile is close to a step function at low degrees of swelling and close to a Gaussian profile at high degrees of swelling. The results obtained from the analysis of the FRAP data are corroborated with NMR diffusometry analysis of SAP with a polyethylene glycol probe having size similar to the Fluorescein. The comparison of the Gaussian and Monotone profile methods is also performed by use of simulated data. It is found that the new Monotone profile method is accurate for all types of initial profiles studied, but it suffers from being computationally slow. The fast Gaussian profile method is sufficiently accurate for most of the profiles studied, but underestimates the diffusion coefficient for profiles close to a step function. We also provide a diagnostic plot, which indicates whether the Gaussian profile method is acceptable or not.
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| 4. |
- Linderbäck, Paula, et al.
(författare)
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The effect of heat- or ultra violet ozone-treatment of titanium on complement deposition from human blood plasma.
- 2010
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 31:18, s. 4795-801
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Tidskriftsartikel (refereegranskat)abstract
- Titanium (Ti) is a well known metallic biomaterial extensively used in dental, orthopaedic-, and occasionally also in blood contacting applications. It integrates well to bone and soft tissues, and is shown upon blood plasma contact to activate the intrinsic pathway of coagulation and bind complement factor 3b. The material properties depend largely on those of the nm-thick dense layer of TiO(2) that becomes rapidly formed upon contact with air and water. The spontaneously formed amorphous Ti-oxide has a pzc approximately 5-6 and its water solubility is at the order of 1-2 micromolar. It is often subjected to chemical- and heat treatments in order to increase the anatase- and rutile crystallinity, to modify the surface topography and to decrease the water solubility. In this work, we prepared sol-gel derived titanium and smooth PVD titanium surfaces, and analysed their oxide and protein deposition properties in human blood plasma before and after annealing at 100-500 degrees C or upon UVO-treatment for up to 96 hours. The blood plasma results show that complement deposition vanished irreversibly after heat treatment at 250-300 degrees C for 30 minutes or after UVO exposure for 24 hours or longer. XPS and infrared spectroscopy indicated change of surface water/hydroxyl binding upon the heat- and UVO treatments, and increased Ti oxidation. XRD analysis confirmed an increased crystallinity and both control (untreated) and annealed smooth titanium displayed low XRD-signals indicating some nanocrystallinity, with predominantly anatase phase. The current results show that the behaviour of titanium dioxide in blood contact can be controlled through relatively simple means, such as mild heating and illumination in UV-light, which both likely irreversibly change the stoichiometry and structure of the outmost layers of titanium dioxide and its OH/H(2)O binding characteristics.
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| 5. |
- Palmquist, Anders, 1977, et al.
(författare)
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Titanium oral implants - surface characteristics, interface biology and clinical outcome
- 2010
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 7:S.5, s. S515-27
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Tidskriftsartikel (refereegranskat)abstract
- Bone-anchored titanium implants have revolutionized oral healthcare. Surface properties of oral titanium implants play decisive roles for molecular interactions, cellular response and bone regeneration. Nevertheless, the role of specific surface properties, such as chemical and phase composition and nanoscale features, for the biological in vivo performance remains to be established. Partly, this is due to limited transfer of state-of-the-art preparation techniques to complex three-dimensional geometries, analytical tools and access to minute, intact interfacial layers. As judged by the available results of a few randomized clinical trials, there is no evidence that any particular type of oral implant has superior long-term success. Important insights into the recruitment of mesenchymal stem cells, cell-cell communication at the interface and high-resolution imaging of the interface between the surface oxide and the biological host are prerequisites for the understanding of the mechanisms of osseointegration. Strategies for development of the next generation of material surface modifications for compromised tissue are likely to include time and functionally programmed properties, pharmacological modulation and incorporation of cellular components.
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| 6. |
- Tobias, Joshua, 1969, et al.
(författare)
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Over-expression of major colonization factors of enterotoxigenic Escherichia coli, alone or together, on non-toxigenic E. coli bacteria
- 2010
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Ingår i: Vaccine. - : Elsevier BV. - 0264-410X .- 1873-2518. ; 28:43, s. 6977-6984
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Tidskriftsartikel (refereegranskat)abstract
- Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and deaths among children in developing countries and the major cause of traveller's diarrhea. Since surface protein colonization factors (CFs) of ETEC are important for pathogenicity and immune protection is mainly mediated by locally produced IgA antibodies in the gut, much effort has focused on the development of an oral CF-based vaccine. We have recently described the development of recombinant strains over-expressing CFA/I; the most prevalent CF among human clinical ETEC isolates. Here, non-toxigenic recombinant E. coli strains over-expressing Coli surface antigen 2 (CS2), CS4, CS5, and CS6, either alone, or each in combination with CFA/I were constructed by cloning the genes required for expression and assembly of each CF into expression vectors harboring a strong promoter. Immunological assays showed that recombinant strains expressing single CFs produced those in significantly larger amounts than did corresponding naturally high producing reference strains. Recombinant strains co-expressing CFA/I together with another CF also expressed significantly larger amounts of both CFs compared with the corresponding references strains. Further, when tested in mice, oral immunization with formalin-killed recombinant bacteria co-expressing one such double-expression CF pair, CFA/I. +. CS2, induced specific serum IgG. +. IgM and fecal IgA antibody responses against both CFs exceeding the responses induced by immunizations with natural reference strains expressing CFA/I and CS2, respectively. We conclude that the described type of recombinant bacteria over-expressing major CFs of ETEC, alone or in combination, may be useful as candidate strains for use in an oral whole-cell CF-ETEC vaccine.
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| 7. |
- Xia, Wei, et al.
(författare)
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Biomineralized strontium-substituted apatite/titanium dioxide coating on titanium surfaces.
- 2010
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Ingår i: Acta biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 6:4, s. 1591-600
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Tidskriftsartikel (refereegranskat)abstract
- Bone mineral is a multi-substituted calcium phosphate. One of these ion substitutions, strontium, has been proven to increase bone strength and decrease bone resorption. Biomimetics is a potential way to prepare surfaces that provide a favorable bone tissue response, thus enhancing the fixation between bone and implants. Here we prepared double-layered strontium-substituted apatite and titanium dioxide coatings on titanium substrates via mimicking bone mineralization. Morphology, crystallinity, surface chemistry and composition of Sr-substituted coatings formed via biomimetic coating deposition on crystalline titanium oxide substrates were studied as functions of soaking temperature and time in phosphate buffer solutions with different Sr ion concentration. The morphology of the biomimetic apatite changed from plate-like for the pure HA to sphere-like for the Sr ion substituted. Surface analysis results showed that 10-33% of Ca ions in the apatite have been substituted by Sr ions, and that the Sr ions were chemically bonded with apatite and successfully incorporated into the structure of apatite.
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| 8. |
- Xia, Wei, et al.
(författare)
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Changes of Surface Composition and Morphology after Incorporation of Ions into Biomimetic Apatite Coating
- 2010
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Ingår i: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 1:1, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- Incorporating trace elements into apatite coatings may permit the combination of several pharmaceutical effects due to the different ions. In this study, strontium, silicon, and fluoride ions have been incorporated into apatite coatings through a biomineralization method, which mimics an in vitro mineralization process. The surface composition was tested with X-ray diffraction and X-ray photoelectron spectroscopy, and the surface morphology was characterized with scanning electron microscopy. Compared with pure hydroxyapatite coating, the strontium, silicon, and fluoride substi-tuted apatite coatings showed different morphologies, such as spherical, needle-like, and nano-flake-like, respectively. The crystal size of these biomimetic hydroxyapatite coatings decreased after ion substitution. The results of the analysis of surface composition showed an increased amount of the ion substitutions with an increase of ion concentrations in the soaking solution. That means the ion incorporation into the apatite structure based on the biomineralization method could not only vary the ion content but also change the morphology of the apatite coatings. Herein, the role of ion sub-stitution is considered from the point of view of materials science at the micro structural and surface chemistry levels.
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