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Document Server@UHasselt (59.068 recursos)

Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.


Mostrando recursos 1 - 20 de 48

  1. Exploring the rhizospheric and endophytic bacterial communities of Acer pseudoplatanus growing on a TNT-contaminated soil: towards the development of a rhizocompetent TNT-detoxifying plant growth promoting consortium

    THIJS, Sofie; Van Dillewijn, Pieter; SILLEN, Wouter; TRUYENS, Sascha; HOLTAPPELS, Michelle; D'HAEN, Jan; CARLEER, Robert; WEYENS, Nele; AMELOOT, Marcel; Ramos, Juan-Luis; VANGRONSVELD, Jaco
    Background and aims Numerous microorganisms have been isolated from trinitrotoluene (TNT)-contaminated soils, however TNT tends to persist, indicating that the microbial biomass or activity is insufficient for degradation. Deep-rooting trees at military sites have been found to take-up contaminants from groundwater, and the extensive root and endosphere provide ideal niches for microbial TNT-transformations. Methods We characterised the rhizosphere, root endosphere and endo-phyllosphere bacteria of Acer pseudoplatanus growing at a historically TNT-contaminated location, using 16S rRNA gene fingerprinting, bacteria isolation, oxidoreductase gene-cloning, in planta growth-promotion (PGP) tests, inoculation, plant physiology measurements and microscopy. Results Based on terminal-restriction-fragment-length-polymorphism analysis, bulk soil and...

  2. Photonic detection and characterization of DNA using sapphire microspheres

    MURIB, Mohammed Sharif; YEAP, Weng Siang; Martens, Daan; Bienstman, Peter; DE CEUNINCK, Ward; VAN GRINSVEN, Bart; Schoening, Michael J.; MICHIELS, Luc; HAENEN, Ken; AMELOOT, Marcel; Serpenguzel, Ali; WAGNER, Patrick
    A microcavity-based deoxyribonucleic acid (DNA) optical biosensor is demonstrated for the first time using synthetic sapphire for the optical cavity. Transmitted and elastic scattering intensity at 1510 nm are analyzed from a sapphire microsphere (radius 500 mu m, refractive index 1.77) on an optical fiber half coupler. The 0.43 nm angular mode spacing of the resonances correlates well with the optical size of the sapphire sphere. Probe DNA consisting of a 36-mer fragment was covalently immobilized on a sapphire microsphere and hybridized with a 29-mer target DNA. Whispering gallery modes (WGMs) were monitored before the sapphire was functionalized with DNA...

  3. Boron-Doped Diamond Functionalization by an Electrografting/Alkyne-Azide Click Chemistry Sequence

    YEAP, Weng Siang; MURIB, Mohammed Sharif; Cuypers, Wim; Liu, Xianjie; VAN GRINSVEN, Bart; AMELOOT, Marcel; Fahlman, Mats; WAGNER, Patrick; MAES, Wouter; HAENEN, Ken
    A straightforward protocol for the covalent functionalization of boron-doped diamond electrodes with either ferrocene or single-stranded deoxyribonucleic acid (DNA) is reported. The functionalization method is based on a combination of diazonium salt electrografting and click chemistry. An azide-terminated organic layer is first electrografted onto the diamond surface by electrochemical reduction of 4-azidophenyldiazonium chloride. The azidophenyl-modified surface then reacts rapidly and efficiently with molecules bearing a terminal alkyne moiety by means of Cu-1-catalyzed alkyne-azide cycloaddition. Covalent attachment of ferrocene moieties was analyzed by X-ray photoelectron spectroscopy and cyclic voltammetry, whereas impedance spectroscopy was applied for the characterization of the immobilized DNA.

  4. Nonlinear Superchiral Meta-Surfaces: Tuning Chirality and Disentangling Non-Reciprocity at the Nanoscale

    Valev, V. K.; Baumberg, J.J.; DE CLERCQ, Ben; Braz, N.; Zheng, X.; Osley, E. J.; Vandendriessche, S.; Hojeij, M.; Blejean, C.; Mertens, Johan; Biris, C. G.; Volskiy, V.; AMELOOT, Marcel; Ekinci, Y.; Vandenbosch, G. A. E.; Warburton, P. A.; Moshchalkov, V. V.; Panoiu, N. C.; Verbiest, T.
    We are grateful to W. Libaers, D. Denkova and Y. Jeyaram (Leuven) for taking linear spectra of the meta-surfaces. We acknowledge financial support from the EPSRC grant EP/G060649/1, ERC LINASS grant 320503, the KU Leuven (CREA, GOA), Methusalem Funding by the Flemish government and the Belgian Inter-University Attraction Poles IAP Programmes. S. V. thanks the FWO-Vlanderen for financial support. B. DC. is thankful to the IWT. JM acknowledges support from the Winton Programme of the Physics of Sustainability.

  5. Impact of differently modified nanocrystalline diamond on the growth of neuroblastoma cells.

    Vaitkuviene, A.; MCDONALD, Matthew; VAHIDPOUR, Farnoosh; NOBEN, Jean-Paul; SANEN, Kathleen; AMELOOT, Marcel; Ratautaite, V.; Kaseta, V.; Biziuleviciene, G.; Ramanaviciene, A.; NESLADEK, Milos; Ramanavicius, A.
    The aim of this study was to assess the impact of nanocrystalline diamond (NCD) thin coatings on neural cell adhesion and proliferation. NCD was fabricated on fused silica substrates by microwave plasma chemical vapor deposition (MPCVD) method. Different surface terminations were performed through exposure to reactive hydrogen and by UV induced oxidation during ozone treatment. Boron doped NCD coatings were also prepared and investigated. NCD surface wettability was determined by contact angle measurement. To assess biocompatibility of the NCD coatings, the neuroblastoma SH-SY5Y cell line was used. Cells were plated directly onto diamond surfaces and cultured in medium with or...

  6. Membrane distribution of the glycine receptor alpha 3 studied by optical super-resolution microscopy

    NOTELAERS, Kristof; Rocha, Susana; PAESEN, Rik; SWINNEN, Nina; Vangindertael, Jeroen; Meier, Jochen C.; RIGO, Jean-Michel; AMELOOT, Marcel; Hofkens, Johan
    In this study, the effect of glycine receptor (GlyR) alpha 3 alternative RNA splicing on the distribution of receptors in the membrane of human embryonic kidney 293 cells is investigated using optical super-resolution microscopy. Direct stochastic optical reconstruction microscopy is used to image both alpha 3K and alpha 3L splice variants individually and together using single-and dual-color imaging. Pair correlation analysis is used to extract quantitative measures from the resulting images. Autocorrelation analysis of the individually expressed variants reveals clustering of both variants, yet with differing properties. The cluster size is increased for alpha 3L compared to alpha 3K (mean...

  7. Syntenin-1 and Ezrin Proteins Link Activated Leukocyte Cell Adhesion Molecule to the Actin Cytoskeleton

    Tudor, Cicerone; te Riet, Joost; Eich, Christina; Harkes, Rolf; SMISDOM, Nick; Wenger, Jessica Bouhuijzen; AMELOOT, Marcel; Holt, Matthew; Kanger, Johannes S.; Figdor, Carl G.; Cambi, Alessandra; Subramaniam, Vinod
    Activated leukocyte cell adhesion molecule (ALCAM) is a type I transmembrane protein member of the immunoglobulin superfamily of cell adhesion molecules. Involved in important pathophysiological processes such as the immune response, cancer metastasis, and neuronal development, ALCAM undergoes both homotypic interactions with other ALCAM molecules and heterotypic interactions with the surface receptor CD6 expressed at the T cell surface. Despite biochemical and biophysical evidence of a dynamic association between ALCAM and the actin cytoskeleton, no detailed information is available about how this association occurs at the molecular level. Here, we exploit a combination of complementary microscopy techniques, including FRET detected...

  8. Human dental pulp stem cells can differentiate into Schwann cells and promote and guide neurite outgrowth in an aligned tissue-engineered collagen construct in vitro

    MARTENS, Wendy; SANEN, Kathleen; Georgiou, Melanie; STRUYS, Tom; BRONCKAERS, Annelies; AMELOOT, Marcel; Phillips, James; LAMBRICHTS, Ivo
    In the present study, we evaluated the differentiation potential of human dental pulp stem cells (hDPSCs) toward Schwann cells, together with their functional capacity with regard to myelination and support of neurite outgrowth in vitro. Successful Schwann cell differentiation was confirmed at the morphological and ultrastructural level by transmission electron microscopy. Furthermore, compared to undifferentiated hDPSCs, immunocytochemistry and ELISA tests revealed increased glial marker expression and neurotrophic factor secretion of differentiated hDPSCs (d-hDPSCs), which promoted survival and neurite outgrowth in 2-dimensional dorsal root ganglia cultures. In addition, neurites were myelinated by d-hDPSCs in a 3-dimensional collagen type I hydrogel neural...

  9. Transport and accumulation of PVP-Hypericin in cancer and normal cells characterized by image correlation spectroscopy techniques

    PENJWEINI, Rozhin; SMISDOM, Nick; DEVILLE, Sarah; AMELOOT, Marcel
    PVP-Hypericin (PVP: polyvinylpyrrolidone) is a potent anti-cancer photosensitizer for photodynamic diagnosis (PDD) and therapy (PDT). However, cellular targets and mechanisms involved in the cancer-selectivity of the photosensitizer are not yet fully understood. This paper gives new insights into the differential transport and localization of PVP-Hypericin in cancer and normal cellswhich are essential to unravel the mechanisms of action and cancer-selectivity. Temporal (TICS) and spatiotemporal (STICS) image correlation spectroscopy are used for the assessment of PVP-Hypericin diffusion and/or velocity in the case of concerted flowin human cervical epithelial HeLa and human lung carcinoma A549 cells, as well as in human primary dendritic...

  10. Cardiac Atrial Appendage Stem Cells Preserve Cardiac Function in a Minipig Acute Myocardial Infarction Model

    FANTON, Yanick; ROBIC, Boris; Daniels, Annick; WINDMOLDERS, Severina; WILLEMS, Leen; Jamaer, Luc; Dubois, Jasperina; Bijnens, Eric; Heuts, Nic; NOTELAERS, Kristof; PAESEN, Rik; AMELOOT, Marcel; Mees, Urbain; RUMMENS, Jean-Luc; HENDRIKX, Marc; HENSEN, Karen; KONINCKX, Remco
    ventricular function; myocardial infarction; magnetic resonance imaging; stem cells

  11. Heat-transfer-based detection of SNPs in the PAH gene of PKU patients

    VANDEN BON, Natalie; VAN GRINSVEN, Bart; MURIB, Mohammed Sharif; YEAP, Weng Siang; HAENEN, Ken; DE CEUNINCK, Ward; WAGNER, Patrick; AMELOOT, Marcel; VERMEEREN, Veronique; MICHIELS, Luc
    Conventional neonatal diagnosis of phenylketonuria is based on the presence of abnormal levels of phenylalanine in the blood. However, for carrier detection and prenatal diagnosis, direct detection of disease-correlated mutations is needed. To speed up and simplify mutation screening in genes, new technologies are developed. In this study, a heat-transfer method is evaluated as a mutation-detection technology in entire exons of the phenylalanine hydroxylase (PAH) gene. This method is based on the change in heat-transfer resistance (Rth) upon thermal denaturation of dsDNA (double-stranded DNA) on nanocrystalline diamond. First, ssDNA (single-stranded DNA) fragments that span the size range of the PAH exons...

  12. Analysis of alpha 3 GlyR single particle tracking in the cell membrane

    NOTELAERS, Kristof; Rocha, Susana; PAESEN, Rik; SMISDOM, Nick; DE CLERCQ, Ben; Meier, Jochen C.; RIGO, Jean-Michel; Hofkens, Johan; AMELOOT, Marcel
    Single particle tracking (SPT) of transmembrane receptors in the plasma membrane often reveals heterogeneous diffusion. A thorough interpretation of the displacements requires an extensive analysis suited for discrimination of differentmotion types present in the data. Here the diffusion pattern of the homomeric ??3-containing glycine receptor (GlyR) is analyzed in themembrane of HEK 293 cells. More specifically, the influence of the ??3 RNA splice variants ??3K and ??3L on lateralmembrane diffusion of the receptor is revealed in detail. Using a combination of ensemble and local SPT analysis, free and anomalous diffusion parameters are determined. The GlyR ??3 free diffusion coefficient is...

  13. Correlating laurdan fluorescence lifetime and generalized polarization in lipid membranes

    Bacalum, Mihaela; Smisdom, Nick; Popescu, A.; Radu, Mihai; Ameloot, Marcel

  14. Ultrafine biofunctionalized SHG-active BaTiO3 towards biomedical applications


  15. Polarization second harmonic generation by image correlation spectroscopy on collagen type I hydrogels

    PAESEN, Rik; SANEN, Kathleen; SMISDOM, Nick; AMELOOT, Marcel; MICHIELS, Luc
    Successful engineering of biomimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from...

  16. Optimizing the antitumor selectivity of PVP-Hypericin re A549 cancer cells and HLF normal cells through pulsed blue light

    PENJWEINI, Rozhin; Loew, Hans G.; Breit, Paul; Kratkya, Karl W.
    Photodynamic therapy (PDT) is based on the preferential accumulation of photosensitizer in cancer cells with subsequent cytotoxicity mediated by singlet oxygen production after light excitation. As photosensitizers accumulate also in the surrounding non-cancer cells, the risk of damaging them by photosensitization is a limitation of PDT. Thus, minimizing the side-effects of PDT on normal cells is one of the challenging problems in medical practice. This paper studies the PDT side-effects of PVP-Hypericin (PVP: polyvinylpyrrolidone) photosensitizer excited with continuous or pulsed irradiation, on combined cell lines of human lung carcinoma epithelial cells (A549) and normal primary human lung fibroblast cells (HLF)....

  17. Measuring the intravitreal mobility of nanomedicines with single-particle tracking microscopy

    Martens, Thomas F.; Vercauteren, Dries; Forier, Katrien; Deschout, Hendrik; Remaut, Katrien; PAESEN, Rik; AMELOOT, Marcel; Engbersen, Johan F. J.; Demeester, Jo; De Smedt, Stefaan C.; Braeckmans, Kevin
    Aim: To develop a robust assay to evaluate and compare the intravitreal mobility of nanoparticles in the intact vitreous body. Materials & methods: Excised bovine eyes were prepared to preserve the fragile structure of the vitreous humor, while permitting high-resolution fluorescence microscopy and single-particle tracking analysis of intravitreally injected nanoparticles. This assay was validated by analyzing polystyrene beads and further employed to evaluate gene nanomedicines composed of poly(amido amine)s and plasmid DNA. Results: The assay was able to distinguish immobilized cationic nanoparticles from mobile PEGylated nanoparticles. PEGylation of the polyplexes resulted in a drastic improvement of their mobility. Conclusion: An...

  18. Automatic Particle Detection in Microscopy Using Temporal Correlations

    Roding, Magnus; Deschout, Hendrik; Martens, Thomas; NOTELAERS, Kristof; Hofkens, Johan; AMELOOT, Marcel; Braeckmans, Kevin; Sarkka, Aila; Rudemo, Mats
    One of the fundamental problems in the analysis of single particle tracking data is the detection of individual particle positions from microscopy images. Distinguishing true particles from noise with a minimum of false positives and false negatives is an important step that will have substantial impact on all further analysis of the data. A common approach is to obtain a plausible set of particles from a larger set of candidate particles by filtering using manually selected threshold values for intensity, size, shape, and other parameters describing a particle. This introduces subjectivity into the analysis and hinders reproducibility. In this paper,...

  19. Implementing heat transfer resistivity as a key element in a nanocrystalline diamond based single nucleotide polymorphism detection array

    Bers, Karolien; VAN GRINSVEN, Bart; VANDENRYT, Thijs; MURIB, Mohammed Sharif; JANSSENS, Wim; Geerets, B.; AMELOOT, Marcel; HAENEN, Ken; MICHIELS, Anneleen; DE CEUNINCK, Ward; WAGNER, Patrick
    In this article, we report on the label-free real-time thermal monitoring of the denaturation of specific DNA fragments and its potential to detect and quantify single nucleotide polymorphisms (SNPs). Probe DNA, consisting of a 36-mer fragment was covalently immobilized on nanocrystalline chemical vapour deposition (CVD) diamond platforms and hybridized with a 29-mer target DNA fragment (full matching and/or with a point mutation). It was observed that the change in heat transfer resistance upon denaturation is dependent on the amount of DNA hybridized to the nanocrystalline diamond (NCD) surface. Furthermore the possibility to distinguish between a full matching sequence and its...

  20. Distinguishing free and anomalous diffusion by rectangular fluorescence recovery after photobleaching: a Monte Carlo study

    De Clercq, Ben; Cleuren, Bart; Deschout, Hendrik; Braeckmans, Kevin; Ameloot, Marcel
    Fluorescence recovery after photobleaching (FRAP) is a common technique to probe mobility of fluorescently labeled proteins in biological membranes by monitoring the time-dependence of the spatially integrated fluorescence signals after a bleaching pulse. Discrimination by FRAP between free diffusion with an immobile fraction (FDIM) and the phenomenological model for anomalous diffusion based on the time-dependent diffusion coefficient (TDDC) is a challenging problem, requiring extremely long observation times for differentiation. Recently, rectangular FRAP (rFRAP) has been introduced for normal diffusion by considering not only the temporal but also spatial information, taking the effective point spread function of the optical system into...

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