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221 results on '"Stokke, Bjørn T."'

2. Buckling initiation in layered hydrogels during transient swelling

Author

Ilseng, Arne, Prot, Victorien, Stokke, Bjørn T., and Skallerud, Bjørn H.

Subjects
Condensed Matter - Soft Condensed Matter, Computer Science - Computational Engineering, Finance, and Science
Abstract

Subjected to compressive stresses, soft polymers with stiffness gradients can display various buckling patterns. These compressive stresses can have different origins, like mechanical forces, temperature changes, or, for hydrogel materials, osmotic swelling. Here, we focus on the influence of the transient nature of osmotic swelling on the initiation of buckling in confined layered hydrogel structures. A constitutive model for transient hydrogel swelling is outlined and implemented as a user-subroutine for the commercial finite element software Abaqus. The finite element procedure is benchmarked against linear perturbation analysis results for equilibrium swelling showing excellent correspondence. Based on the finite element results we conclude that the initiation of buckling in a two-layered hydrogel structure is highly affected by transient swelling effects, with instability emerging at lower swelling ratios and later in time with a lower diffusion coefficient. In addition, for hard-on-soft systems the wavelength of the buckling pattern is found to decrease as the diffusivity of the material is reduced for gels with a relatively low stiffness gradient between the substrate and the upper film. This study highlights the difference between equilibrium and transient swelling when it comes to the onset of instability in hydrogels, which is believed to be of importance as a fundamental aspect of swelling as well as providing input to guiding principles in the design of specific hydrogel systems.

Published
2019
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3. Plasma Treatment of PDMS for Microcontact Printing (μCP) of Lectins Decreases Silicone Transfer and Increases the Adhesion of Bladder Cancer Cells

Author

Zemła, Joanna, primary, Szydlak, Renata, additional, Gajos, Katarzyna, additional, Kozłowski, Łukasz, additional, Zieliński, Tomasz, additional, Luty, Marcin, additional, Øvreeide, Ingrid H., additional, Prot, Victorien E., additional, Stokke, Bjørn T., additional, and Lekka, Małgorzata, additional

Published
2023
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17. List of Contributors

Author

Al-Maharik, Nawaf, primary, Annuk, Heidi, additional, Apicella, Michael A., additional, Appelmelk, Ben J., additional, Boneca, Ivo G., additional, Born, Petra, additional, Brandenburg, Klaus, additional, Brennan, Patrick J., additional, Briken, Volker, additional, Brown, Eric D., additional, Carrington, Stephen D., additional, Cescutti, Paola, additional, Chatterjee, Delphi, additional, Clyne, Marguerite, additional, Cooper, Richard M., additional, Corfield, Anthony P., additional, Cunneen, Monica M., additional, de Groot, Piet W.J., additional, De Libero, Gennaro, additional, de los Reyes-Gavilán, Clara G., additional, Doering, Tamara L., additional, Dow, Max, additional, Driessen, Nicole N., additional, Dyason, Jeffrey C., additional, Egelseer, Eva Maria, additional, Elbein, Alan D., additional, Feldman, Mario F., additional, Fitz Patrick, Eamonn, additional, Fujimoto, Yukari, additional, Fukase, Koichi, additional, Garidel, Patrick, additional, Geurtsen, Jeroen, additional, Gonzalez, Marlyn, additional, Grice, I. Darren, additional, Guerry, Patricia, additional, Gutsmann, Thomas, additional, Heine, Holger, additional, Heng, Joanne, additional, Holst, Otto, additional, Jennings, Harold. J, additional, Jennings, Michael P., additional, Kanipes, Margaret I., additional, Kasper, Dennis L., additional, Khamri, Wafa, additional, Kiefel, Milton J., additional, Klein, Dionne C.G., additional, Klis, Frans M., additional, Knirel, Yuriy A., additional, Kohler, Thomas, additional, Kosma, Paul, additional, Kulauzovic, Emir, additional, Kusumoto, Shoichi, additional, Lawrence, John R., additional, Lingwood, Clifford A., additional, Lipke, Peter N., additional, Logan, Susan M., additional, Mahfoud, Radia, additional, McConville, Malcolm J., additional, McLoughlin, Rachel M., additional, Messner, Paul, additional, Molinaro, Antonio, additional, Moran, Anthony P., additional, Naderer, Thomas, additional, Neu, Thomas R., additional, Newman, Mari-Anne, additional, Nikolaev, Andrei V., additional, Pedersen, Christian M., additional, Pereira, Mark P., additional, Peschel, Andreas, additional, Pöhlmann, Stefan, additional, Pon, Robert A., additional, Ralph, Stuart A., additional, Reeves, Peter R., additional, Reid, Anne N., additional, Reid, Colm J., additional, Reilly, Morgann C., additional, Riekenberg, Sabine, additional, Ruas-Madiedo, Patricia, additional, Salazar, Nuria, additional, Schäffer, Christina, additional, Schmidt, Richard R., additional, Schoenhofen, Ian C., additional, Sletmoen, Marit, additional, Sleytr, Uwe B., additional, Soo, Evelyn C., additional, Steffen, Imke, additional, Stein, Daniel C., additional, Stokke, Bjørn T., additional, Szymanski, Christine M., additional, Tiralongo, Joe, additional, Tee, Jennifer A., additional, Thursz, Mark R., additional, Trent, M. Stephen, additional, Tsegaye, Theodros S., additional, Heijenoort, Jean van, additional, Vollmer, Waldemar, additional, Itzstein, Mark von, additional, Wilson, Jennifer C., additional, and Xia, Guoqing, additional

Published
2010
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28. Small angle x-ray scattering study of local structure and collapse transition of (1,3)-β-D-glucan-chitosan gels.

Author

Sletmoen, Marit, Stokke, Bjørn T., and Geissler, Erik

Subjects
*X-ray scattering, *POLYMERS, *ORGANIC compounds, *COLLOIDS, *GELATION, *POLYSACCHARIDES
Abstract

Scleroglucan is a (1,3)-β-D-glucan polysaccharide produced by the fungus Sclerotium. Dissolved in water at room temperature it adopts a linear, rigid, triple helical structure. Gelation of scleroglucan can be obtained by Schiff-base formation between partly periodate oxidized scleroglucan and the primary amine groups of chitosan. The scleraldehyde-chitosan gels exhibit a collapse transition when exposed to volume fractions of isopropanol, Wp, larger than 65%. The aim of the present study is to provide structural information concerning the local polymer distribution and the collapse transition in (1,3)-β-D-glucan-chitosan gels. Small angle x-ray scattering was used to investigate solutions and gels of scleroglucan in water, as well as in an aqueous mixture containing 65% isopropanol. The results reveal that in aqueous solution, the polysaccharide scleroglucan chains have an approximately cylindrical cross section of external diameter close to 17 Å. The gels display the same local structure, but form clusters on a longer distance scale. For the collapsed gels in the water-isopropanol mixture, partial phase separation occurs in which ordered domains of approximate size of 110 Å develop. This study indicates that local ordering in liquid-crystalline-type domains is a possible molecular mechanism contributing to the collapse of gels composed of semiflexible polymers. The triple helical structure of the molecule appears not to be conserved in the majority phase in this solvent, but it is conserved in the liquid crystalline domains. [ABSTRACT FROM AUTHOR]

Published
2006
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30. Novel imaging technologies for characterization of microbial extracellular polysaccharides

Author

Lilledahl, Magnus B. and Stokke, Bjørn T.

Subjects
superresolution optical microscopy, lcsh:QR1-502, high resolution AFM, dynamics, Review, AFM, Microbiology, SHG, lcsh:Microbiology
Abstract

Understanding of biology is underpinned by the ability to observe structures at various length scales. This is so in a historical context and is also valid today. Evolution of novel insight often emerges from technological advancement. Recent developments in imaging technologies that is relevant for characterization of extraceullar microbiological polysaccharides are summarized. Emphasis is on scanning probe and optical based techniques since these tools offers imaging capabilities under aqueous conditions more closely resembling the physiological state than other ultramicroscopy imaging techniques. Following the demonstration of the scanning probe microscopy principle, novel operation modes to increase data capture speed toward video rate, exploitation of several cantilever frequencies, and advancement of utilization of specimen mechanical properties as contrast, also including their mode of operation in liquid, have been developed on this platform. Combined with steps in advancing light microscopy with resolution beyond the far field diffraction limit, non-linear methods, and combinations of the various imaging modalities, the potential ultramicroscopy toolbox available for characterization of exopolysaccharides (EPS) are richer than ever. Examples of application of such ultramicroscopy strategies range from imaging of isolated microbial polysaccharides, structures being observed when they are involved in polyelectrolyte complexes, aspects of their enzymatic degradation, and cell surface localization of secreted polysaccharides. These, and other examples, illustrate that the advancement in imaging technologies relevant for EPS characterization supports characterization of structural aspects. © 2015 Lilledahl and Stokke. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Published
2015

34. Tubulin-Targeted Therapy in Melanoma Increases the Cell Migration Potential by Activation of the Actomyosin Cytoskeleton─An In Vitro Study

Author

Luty, Marcin, Szydlak, Renata, Pabijan, Joanna, Zemła, Joanna, Oevreeide, Ingrid H., Prot, Victorien E., Stokke, Bjørn T., Lekka, Malgorzata, and Zapotoczny, Bartlomiej

Abstract

One of the most dangerous aspects of cancers is their ability to metastasize, which is the leading cause of death. Hence, it holds significance to develop therapies targeting the eradication of cancer cells in parallel, inhibiting metastases in cells surviving the applied therapy. Here, we focused on two melanoma cell lines─WM35 and WM266-4─representing the less and more invasive melanomas. We investigated the mechanisms of cellular processes regulating the activation of actomyosin as an effect of colchicine treatment. Additionally, we investigated the biophysical aspects of supplement therapy using Rho-associated protein kinase (ROCK) inhibitor (Y-27632) and myosin II inhibitor ((−)-blebbistatin), focusing on the microtubules and actin filaments. We analyzed their effect on the proliferation, migration, and invasiveness of melanoma cells, supported by studies on cytoskeletal architecture using confocal fluorescence microscopy and nanomechanics using atomic force microscopy (AFM) and microconstriction channels. Our results showed that colchicine inhibits the migration of most melanoma cells, while for a small cell population, it paradoxically increases their migration and invasiveness. These changes are also accompanied by the formation of stress fibers, compensating for the loss of microtubules. Simultaneous administration of selected agents led to the inhibition of this compensatory effect. Collectively, our results highlighted that colchicine led to actomyosin activation and increased the level of cancer cell invasiveness. We emphasized that a cellular pathway of Rho-ROCK-dependent actomyosin contraction is responsible for the increased invasive potential of melanoma cells in tubulin-targeted therapy.

Published
2024
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