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  • 1.
    Aadland, Reidun C.
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Akarri, Salem
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU Norwegian University of Science and Technology, Norway.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    A core flood and microfluidics investigation of nanocellulose as a chemical additive to water flooding for eor2020In: Nanomaterials, E-ISSN 2079-4991, Vol. 10, no 7, article id 1296Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)- oxidized cellulose nanofibrils (T-CNFs) were tested as enhanced oil recovery (EOR) agents through core floods and microfluidic experiments. Both particles were mixed with low salinity water (LSW). The core floods were grouped into three parts based on the research objectives. In Part 1, secondary core flood using CNCs was compared to regular water flooding at fixed conditions, by reusing the same core plug to maintain the same pore structure. CNCs produced 5.8% of original oil in place (OOIP) more oil than LSW. For Part 2, the effect of injection scheme, temperature, and rock wettability was investigated using CNCs. The same trend was observed for the secondary floods, with CNCs performing better than their parallel experiment using LSW. Furthermore, the particles seemed to perform better under mixed-wet conditions. Additional oil (2.9–15.7% of OOIP) was produced when CNCs were injected as a tertiary EOR agent, with more incremental oil produced at high temperature. In the final part, the effect of particle type was studied. T-CNFs produced significantly more oil compared to CNCs. However, the injection of T-CNF particles resulted in a steep increase in pressure, which never stabilized. Furthermore, a filter cake was observed at the core face after the experiment was completed. Microfluidic experiments showed that both T-CNF and CNC nanofluids led to a better sweep efficiency compared to low salinity water flooding. T- CNF particles showed the ability to enhance the oil recovery by breaking up events and reducing the trapping efficiency of the porous medium. A higher flow rate resulted in lower oil recovery factors and higher remaining oil connectivity. Contact angle and interfacial tension measurements were conducted to understand the oil recovery mechanisms. CNCs altered the interfacial tension the most, while T-CNFs had the largest effect on the contact angle. However, the changes were not significant enough for them to be considered primary EOR mechanisms.

  • 2.
    Aadland, Reidun C.
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Dziuba, Carter J.
    University of Calgary, Canada.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    Holt, Thorleif
    SINTEF, Norway.
    Gates, Ian D.
    University of Calgary, Canada.
    Bryant, Steven L.
    University of Calgary, Canada.
    Identification of nanocellulose retention characteristics in porous media2018In: Nanomaterials, E-ISSN 2079-4991, Vol. 8, no 7, article id 547Article in journal (Refereed)
    Abstract [en]

    The application of nanotechnology to the petroleum industry has sparked recent interest in increasing oil recovery, while reducing environmental impact. Nanocellulose is an emerging nanoparticle that is derived from trees or waste stream from wood and fiber industries. Thus, it is taken from a renewable and sustainable source, and could therefore serve as a good alternative to current Enhanced Oil Recovery (EOR) technologies. However, before nanocellulose can be applied as an EOR technique, further understanding of its transport behavior and retention in porous media is required. The research documented in this paper examines retention mechanisms that occur during nanocellulose transport. In a series of experiments, nanocellulose particles dispersed in brine were injected into sandpacks and Berea sandstone cores. The resulting retention and permeability reduction were measured. The experimental parameters that were varied include sand grain size, nanocellulose type, salinity, and flow rate. Under low salinity conditions, the dominant retention mechanism was adsorption and when salinity was increased, the dominant retention mechanism shifted towards log-jamming. Retention and permeability reduction increased as grain size decreased, which results from increased straining of nanocellulose aggregates. In addition, each type of nanocellulose was found to have significantly different transport properties. Experiments with Berea sandstone cores indicate that some pore volume was inaccessible to the nanocellulose. As a general trend, the larger the size of aggregates in bulk solution, the greater the observed retention and permeability reduction. Salinity was found to be the most important parameter affecting transport. Increased salinity caused additional aggregation, which led to increased straining and filter cake formation. Higher flow rates were found to reduce retention and permeability reduction. Increased velocity was accompanied by an increase in shear, which is believed to promote breakdown of nanocellulose aggregates. © 2018 by the authors.

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  • 3.
    Aadland, Reidun
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Jakobsen, Trygve
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Long-Sanouiller, Haili
    NTNU Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Paso, Kristofer
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    High-temperature core flood investigation of nanocellulose as a green additive for enhanced oil recovery2019In: Nanomaterials, E-ISSN 2079-4991, Vol. 9, no 5, article id 665Article in journal (Refereed)
    Abstract [en]

    Recent studies have discovered a substantial viscosity increase of aqueous cellulose nanocrystal (CNC) dispersions upon heat aging at temperatures above 90 °C. This distinct change in material properties at very low concentrations in water has been proposed as an active mechanism for enhanced oil recovery (EOR), as highly viscous fluid may improve macroscopic sweep efficiencies and mitigate viscous fingering. A high-temperature (120 °C) core flood experiment was carried out with 1 wt.% CNC in low salinity brine on a 60 cm-long sandstone core outcrop initially saturated with crude oil. A flow rate corresponding to 24 h per pore volume was applied to ensure sufficient viscosification time within the porous media. The total oil recovery was 62.2%, including 1.2% oil being produced during CNC flooding. Creation of local log-jams inside the porous media appears to be the dominant mechanism for additional oil recovery during nano flooding. The permeability was reduced by 89.5% during the core flood, and a thin layer of nanocellulose film was observed at the inlet of the core plug. CNC fluid and core flood effluent was analyzed using atomic force microscopy (AFM), particle size analysis, and shear rheology. The effluent was largely unchanged after passing through the core over a time period of 24 h. After the core outcrop was rinsed, a micro computed tomography (micro-CT) was used to examine heterogeneity of the core. The core was found to be homogeneous. © 2019 by the authors.

  • 4.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Brodin, Fredrik Wernersson
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Simon, Sébastien
    Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils-The Effects of Ionic Strength and pH.2019In: Nanomaterials, E-ISSN 2079-4991, Vol. 9, no 2, article id E259Article in journal (Refereed)
    Abstract [en]

    Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the presence of NaCl and acetic acid, at concentrations relevant to food applications. Food emulsions may be an important future application area for CNFs due to their availability and excellent viscosifying abilities. The emulsion characterization was carried out by visual inspection, light microscopy, viscosity measurements, dynamic light scattering and mild centrifugation, which showed that stable emulsions could be obtained for both CNF qualities in the absence of salt and acid. In addition, the enzymatically stabilized CNFs were able to stabilize emulsions in the presence of acid and NaCl, with little change in the appearance or droplet size distribution over one month of storage at room temperature. The work showed that enzymatically treated CNFs could be suitable for use in food systems where NaCl and acid are present, while the more highly charged TEMPO-CNFs might be more suited for other applications, where they can contribute to a high emulsion viscosity even at low concentrations.

  • 5.
    Aarstad, Olav
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Pedersen, Ina Sander
    NTNU Norwegian University of Science and Technology, Norway.
    Björnöy, Sindre H.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils2017In: Polymers, E-ISSN 2073-4360, Vol. 9, no 8, article id 378Article in journal (Refereed)
    Abstract [en]

    Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.

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  • 6.
    Campodoni, E.
    et al.
    CNR National Research Council, Italy.
    Montanari, M.
    CNR National Research Council, Italy.
    Dozio, S. M.
    CNR National Research Council, Italy.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Panseri, S.
    CNR National Research Council, Italy.
    Montesi, M.
    CNR National Research Council, Italy.
    Tampieri, A.
    CNR National Research Council, Italy.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU Norwegian University of Science and Technology, Norway.
    Sandri, M.
    CNR National Research Council, Italy.
    Blending gelatin and cellulose nanofibrils: Biocomposites with tunable degradability and mechanical behavior2020In: Nanomaterials, E-ISSN 2079-4991, Vol. 10, no 6, article id 1219Article in journal (Refereed)
    Abstract [en]

    Many studies show how biomaterial properties like stiffness, mechanical stimulation and surface topography can influence cellular functions and direct stem cell differentiation. In this work, two different natural materials, gelatin (Gel) and cellulose nanofibrils (CNFs), were combined to design suitable 3D porous biocomposites for soft-tissue engineering. Gel was selected for its well-assessed high biomimicry that it shares with collagen, from which it derives, while the CNFs were chosen as structural reinforcement because of their exceptional mechanical properties and biocompatibility. Three different compositions of Gel and CNFs, i.e., with weight ratios of 75:25, 50:50 and 25:75, were studied. The biocomposites were morphologically characterized and their total-and macro-porosity assessed, proving their suitability for cell colonization. In general, the pores were larger and more isotropic in the biocomposites compared to the pure materials. The influence of freeze-casting and dehydrothermal treatment (DHT) on mechanical properties, the absorption ability and the shape retention were evaluated. Higher content of CNFs gave higher swelling, and this was attributed to the pore structure. Cross-linking between CNFs and Gel using DHT was confirmed. The Young’s modulus increased significantly by adding the CNFs to Gel with a linear relationship with respect to the CNF amounts. Finally, the biocomposites were characterized in vitro by testing cell colonization and growth through a quantitative cell viability analysis performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, the cell viability analysis was performed by the means of a Live/Dead test with Human mesenchymal stem cells (hMSCs). All the biocomposites had higher cytocompatibility compared to the pure materials, Gel and CNFs. © 2020 by the authors. 

  • 7.
    Campodoni, Elisabetta
    et al.
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Rashad, Ahmad
    University of Bergen, Norway.
    Ramírez-Rodríguez, Gloria B.
    Universidad de Granada, Spain.
    Mustafa, Kamal
    University of Bergen, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    Tampieri, Anna
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Sandri, Monica
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Polymeric 3D scaffolds for tissue regeneration: Evaluation of biopolymer nanocomposite reinforced with cellulose nanofibrils2019In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 94, p. 867-878Article in journal (Refereed)
    Abstract [en]

    Biopolymers such as gelatin (Gel) and cellulose nanofibrils (CNF) have many of the essential requirements for being used as scaffolding materials in tissue regeneration; biocompatibility, surface chemistry, ability to generate homogeneous hydrogels and 3D structures with suitable pore size and interconnection, which allows cell colonization and proliferation. The purpose of this study was to investigate whether the mechanical behaviour of the Gel matrix can be improved by means of functionalization with cellulose nanofibrils and proper cross-linking treatments. Blending processes were developed to achieve a polymer nanocomposite incorporating the best features of both biopolymers: biomimicry of the Gel and structural reinforcement by the CNF. The designed 3D structures underline interconnected porosity achieved by freeze-drying process, improved mechanical properties and chemical stability that are tailored by CNF addition and different cross-linking approaches. In vitro evaluations reveal the preservation of the biocompatibility of Gel and its good interaction with cells by promoting cell colonization and proliferation. The results support the addition of cellulose nanofibrils to improve the mechanical behaviour of 3D porous structures suitable as scaffolding for tissue regeneration.

  • 8.
    Cernencu, Alexandra
    et al.
    University Politehnica of Bucharest, Romania.
    Lungu, Adriana
    University Politehnica of Bucharest, Romania.
    Stancu, Izabela
    University Politehnica of Bucharest, Romania.
    Serafim, Andrada
    University Politehnica of Bucharest, Romania.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Iovu, Horia
    University Politehnica of Bucharest, Romania; Academy of Romanian Scientists, Romania.
    Bioinspired 3D printable pectin-nanocellulose ink formulations2019In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 220, p. 12-21Article in journal (Refereed)
    Abstract [en]

    The assessment of several ink formulations for 3D printing based on two natural macromolecular compounds is presented. In the current research we have exploited the fast crosslinking potential of pectin and the remarkable shear-thinning properties of carboxylated cellulose nanofibrils, which is known to induce a desired viscoelastic behavior. Prior to 3D printing, the viscoelastic properties of the polysaccharide inks were evaluated by rheological measurements and injectability tests. The reliance of the printing parameters on the ink composition was established through one-dimensional lines printing, the base units of 3D-structures. The performance of the 3D-printed structures after ionic cross-linking was evaluated in terms of mechanical properties and rehydration behavior. MicroCT was also used to evaluate the morphology of the 3D-printed objects regarding the effect of pectin/nanocellulose ratio on the geometrical features of scaffolds. The proportionality between the two polymers proved to be the determining factor for the firmness and strength of the printed objects. © 2019

  • 9.
    Chinga-Carrasco, Gary
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Johansson, Jenny
    RISE Research Institutes of Sweden, Materials and Production.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Leirset, Ingebjørg
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Björn, Camilla
    RISE Research Institutes of Sweden, Materials and Production, Chemistry, Biomaterials and Textiles.
    Agrenius, Karin
    RISE Research Institutes of Sweden, Materials and Production, Chemistry, Biomaterials and Textiles.
    Stevanic Srndovic, Jasna
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Håkansson, Joakim
    RISE Research Institutes of Sweden, Materials and Production, Chemistry, Biomaterials and Textiles. Gothenburg University, Sweden.
    Characterization and Antibacterial Properties of Autoclaved Carboxylated Wood Nanocellulose.2021In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 22, no 7, p. 2779-2789Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) were obtained by applying a chemical pretreatment consisting of autoclaving the pulp fibers in sodium hydroxide, combined with 2,2,6,6-tetramethylpiperidinyl-1-oxyl-mediated oxidation. Three levels of sodium hypochlorite were applied (2.5, 3.8, and 6.0 mmol/g) to obtain CNF qualities (CNF_2.5, CNF_3.8, and CNF_6.0) with varying content of carboxyl groups, that is, 1036, 1285, and 1593 μmol/g cellulose. The cytotoxicity and skin irritation potential (indirect tests) of the CNFs were determined according to standardized in vitro testing for medical devices. We here demonstrate that autoclaving (121 °C, 20 min), which was used to sterilize the gels, caused a modification of the CNF characteristics. This was confirmed by a reduction in the viscosity of the gels, a morphological change of the nanofibrils, by an increase of the ultraviolet-visible absorbance maxima at 250 nm, reduction of the absolute zeta potential, and by an increase in aldehyde content and reducing sugars after autoclaving. Fourier-transform infrared spectroscopy and wide-angle X-ray scattering complemented an extensive characterization of the CNF gels, before and after autoclaving. The antibacterial properties of autoclaved carboxylated CNFs were demonstrated in vitro (bacterial survival and swimming assays) on Pseudomonas aeruginosa and Staphylococcus aureus. Importantly, a mouse in vivo surgical-site infection model on S. aureus revealed that CNF_3.8 showed pronounced antibacterial effect and performed as good as the antiseptic Prontosan wound gel.

  • 10.
    Chiulan, Ioana
    et al.
    The National Institute for Research and Development in Chemistry and Petrochemistry, Romania; Advanced Polymer Materials Group, University Politehnica of Bucharest, Romania.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Voicu, Stefan
    Chinga-Carrasco, Gary
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Photopolymerization of Bio-Based Polymers in a Biomedical Engineering Perspective2021In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 22, no 5, p. 1795-1814Article in journal (Refereed)
    Abstract [en]

    Photopolymerization is an effective method to covalently cross-link polymer chains that can be shaped into several biomedical products and devices. Additionally, polymerization reaction may induce a fluid-solid phase transformation under physiological conditions and is ideal for in vivo cross-linking of injectable polymers. The photoinitiator is a key ingredient able to absorb the energy at a specific light wavelength and create radicals that convert the liquid monomer solution into polymers. The combination of photopolymerizable polymers, containing appropriate photoinitiators, and effective curing based on dedicated light sources offers the possibility to implement photopolymerization technology in 3D bioprinting systems. Hence, cell-laden structures with high cell viability and proliferation, high accuracy in production, and good control of scaffold geometry can be biofabricated. In this review, we provide an overview of photopolymerization technology, focusing our efforts on natural polymers, the chemistry involved, and their combination with appropriate photoinitiators to be used within 3D bioprinting and manufacturing of biomedical devices. The reviewed articles showed the impact of different factors that influence the success of the photopolymerization process and the final properties of the cross-linked materials.

  • 11.
    Courtade, Gaston
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Forsberg, Zarah
    NMBU Norwegian University of Life Sciences, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Eijsink, Vincent G H
    NMBU Norwegian University of Life Sciences, Norway.
    Aachmann, Finn L
    NTNU Norwegian University of Science and Technology, Norway.
    The carbohydrate-binding module and linker of a modular lytic polysaccharide monooxygenase promote localized cellulose oxidation2018In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 293, no 34, p. 13006-13015Article in journal (Refereed)
    Abstract [en]

    Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that catalyze the oxidative cleavage of polysaccharides such as cellulose and chitin, a feature that makes them key tools in industrial biomass conversion processes. The catalytic domains of a considerable fraction of LPMOs and other carbohydrate-active enzymes (CAZymes) are tethered to carbohydrate-binding modules (CBMs) by flexible linkers. These linkers preclude X-ray crystallographic studies, and the functional implications of these modular assemblies remain partly unknown. Here, we used NMR spectroscopy to characterize structural and dynamic features of full-length modular ScLPMO10C from Streptomyces coelicolor We observed that the linker is disordered and extended, creating distance between the CBM and the catalytic domain and allowing these domains to move independently of each other. Functional studies with cellulose nanofibrils revealed that most of the substrate-binding affinity of full-length ScLPMO10C resides in the CBM. Comparison of the catalytic performance of full-length ScLPMO10C and its isolated catalytic domain revealed that the CBM is beneficial for LPMO activity at lower substrate concentrations and promotes localized and repeated oxidation of the substrate. Taken together, these results provide a mechanistic basis for understanding the interplay between catalytic domains linked to CBMs in LPMOs and CAZymes in general.

  • 12.
    El Miri, N.
    et al.
    Mid Sweden University, Sweden.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Wallsten, Sara
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Svedberg, Anna
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Norgren, Magnus
    Mid Sweden University, Sweden.
    A comprehensive investigation on modified cellulose nanocrystals and their films properties2022In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 219, p. 998-1008Article in journal (Refereed)
    Abstract [en]

    In this work, we aimed to tune cellulose nanocrystals (CNCs) properties by introducing different functional groups (aldehyde, carboxyl, silane, and ammonium groups) on the surface through different chemical modifications. These functional groups were obtained by combining: the periodate oxidation with TEMPO-oxidation, aminosylation or cationization. CNCs produced and their films were characterized to elucidate their performances. The results showed that the properties of obtained CNCs varied depending on the grafted functionalities on the surface. The results reveal that after each modification a colloidal stability is preserved. Interestingly, Periodate oxidation of cellulose nanocrystals results in film components that interact through intra- and intermolecular hemiacetals and lead to films with a tensile strength of 116 MPa compared to the pristine CNCs, in contrast the subsequent modifications led to lower tensile strength. Of note, remarkable thermal stability has been achieved after modifications reaching a maximum of 280 °C. The oxygen barrier properties of the films after modifications varied between 0.48 and 0.54 cm3μm/(m2d*kPa) at 50 % RH. 

  • 13.
    Fall, Andreas
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Henriksson, Marielle
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Karppinen, A.
    Borregaard, Norway.
    Opstad, A.
    Borregaard, Norway.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    The effect of ionic strength and pH on the dewatering rate of cellulose nanofibril dispersions2022In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 29, no 14, p. 7649-7662Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils, CNFs, show great potential in many application areas. One main aspect limiting the industrial use is the slow and energy demanding dewatering of CNF suspensions. Here we investigate the dewatering with a piston press process. Three different CNF grades were dewatered to solid contents between approx. 20 and 30%. The CNF grades varied in charge density (30, 106 and 604 µmol/g) and fibrillation degree. The chemical conditions were varied by changing salt concentration (NaCl) and pH and the dewatering rates were compared before and after these changes. For the original suspensions, a higher charge provides slower dewatering with the substantially slowest dewatering for the highest charged CNFs. However, by changing the conditions it dewatered as fast as the two lower charged CNFs, even though the salt/acid additions also improved the dewatering rate for these two CNFs. Finally, by tuning the conditions, fast dewatering could be obtained with only minor effect on film properties (strength and oxygen barrier) produced from redispersed dispersion. However, dewatering gives some reduction in viscosity of the redispersed dispersions. This may be a disadvantage if the CNF application is as e.g. rheology modifier or emulsion stabilizer. Graphical abstract: [Figure not available: see fulltext.].

  • 14.
    Heggset, Ellinor B
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Aaen, Ragnhild
    NTNU Norwegian University of Science and Technology, Norway.
    Veslum, Trinelise
    Mills AS, Norway.
    Henriksson, Marielle
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU Norwegian University of Science and Technology, Norway.
    Cellulose nanofibrils as rheology modifier in mayonnaise – A pilot scale demonstration2020In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 108, article id 106084Article in journal (Refereed)
    Abstract [en]

    The applicability of cellulose nanofibrils (CNFs) as viscosifying agent in a starch-reduced low-fat mayonnaise and in an oil-reduced full-fat mayonnaise has been considered. For low-fat mayonnaise a 50 wt% reduction in the ordinary starch content was performed, while for full-fat mayonnaise, the oil content was reduced from 79 to 70 wt%. To study if the stability was affected when CNFs were added, analyses as visual and accelerated stability tests, droplet size measurements and rheology studies, determining the shear viscosity, and the loss and storage moduli, were conducted after 1 day, 1 week and 1 month of storage in room temperature. Even though changes in droplet size distributions and rheological properties indicated some coalescence, the visual stability was not changed after 1 month of storage for any of the samples. The decrease in viscosity and moduli inflicted by reduction of starch or fat, could be regained by the addition of CNFs at 0.75 wt % and 0.42 wt %, respectively. Based on the results in this work, mayonnaise with reduced starch or fat content can be produced when CNFs are used as a viscosifying agent.

  • 15.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Temperature stability of nanocellulose dispersions2017In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 157, p. 114-121Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNF) have potential as rheology modifiers of water based fluids, e.g. drilling fluids for use in oil wells or as additives in injection water for enhanced oil recovery (EOR). The temperature in oil wells can be high (>100 °C), and the retention time long; days for drilling fluids and months for EOR fluids. Hence, it is important to assess the temperature stability over time of nanocellulose dispersions to clarify their suitability as rheology modifiers of water based fluids at such harsh conditions. Dispersions of CNF produced mechanically, by using TEMPO mediated oxidation and by using carboxymethylation as pretreatment, in addition to cellulose nanocrystals (CNC), have been subjected to heat aging. Temperature stability was best for CNC and for mechanically produced CNF that were stable after heating to 140 °C for three days. The effect of additives was evaluated; cesium formate and sodium formate increased the temperature stability of the dispersions, while there was no effect of using phosphate buffer.

  • 16.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Sundby, Kristin W.
    Borregaard, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Viscoelastic properties of nanocellulose based inks for 3D printing and mechanical properties of CNF/alginate biocomposite gels2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, no 1, p. 581-595Article in journal (Refereed)
    Abstract [en]

    Inks for 3D printing based on cellulose nanofibrils (CNFs) or mixtures of CNFs and either cellulose nanocrystals (CNCs) or alginate were assessed by determining their viscoelastic properties i.e. complex viscosity and storage and loss moduli (G′ and G″). Two types of alginates were used, i.e. from Laminaria hyperborea stipe and Macrocystis pyrifera. Shape fidelity of 3D printed grids were qualitatively evaluated and compared to the viscoelastic properties of the inks. The biocomposite gels containing alginate were post stabilized by crosslinking with Ca2+. Mechanical properties of the crosslinked biocomposite gels were assessed. The complex viscosity, G′ and G″ of CNF suspensions increased when the solid content was increased from 3.5 to 4.0 wt%, but levelled off by further increase in CNF solid content. The complex viscosity at low angular frequency at 4 wt% was as high as 104 Pa·s. This seemed to be the necessary viscosity level for obtaining good shape fidelity of the printed structures for the studied systems. By replacing part of the CNFs with CNCs, the complex viscosity, G′ and G″ were reduced and so was also the shape fidelity of the printed grids. The changes in complex viscosity and moduli when CNFs was replaced with alginate depended on the relative amounts of CNFs/alginate. The type of alginate (from either L. hyp. stipe or M. pyr.) did not play a role for the viscoelastic properties of the inks, nor for the printed grids before post stabilization. Replacing CNFs with up to 1.5 wt% alginate gave satisfactory shape fidelity. The effect of adding alginate and subsequent crosslinking with Ca2+, strongly affected the strength properties of the gels. By appropriate choice of relative amounts of CNFs and alginate and type of alginate, the Young’s modulus and rupture strength could be controlled within the range of 30–150 kPa and 1.5–6 kg, respectively. The deformation at rupture was around 55%. The alginate from L. hyp. stipe yields higher Young’s modulus and lower syneresis compared to M. pyr. This shows that the choice of alginate plays a significant role for the mechanical properties of the final product, although it does not influence on the viscoelastic properties of the ink. The choice of alginate should be L. hyp. stipe if high strength is desired.

  • 17. Heggset, Ellinor B
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Øyaas, Karin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Novel pretreatment pathways for dissolution of lignocellulosic biomass based on ionic liquid and low temperature alkaline treatment2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 93, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Pretreatment, fractionation and hydrolysis remains costly and challenging process steps in biochemical conversion of softwoods. Here, ionic liquid pretreatment using 1-ethyl-3-methylimidazolium acetate (EMIM-OAc) at high temperature (100 °C, 6 h) and alkali based (NaOH/urea) pretreatment at sub-zero temperature (−18 °C, 24 h) were compared and combined in studies of Norway Spruce biomass deconstruction. Both treatments significantly improved the enzymatic digestibility of the biomass. EMIM-OAc gave higher glucan than mannan digestibility, indicating a more pronounced effect on the cellulose polymer than on the hemicellulose polymer. In contrast, low temperature alkali pretreatment using NaOH or NaOH + urea gave a more pronounced effect on mannan than on glucan digestibility. By combining the two methods the total monosugar yield after enzymatic hydrolysis was improved by 20–50% as compared to using ionic liquid or alkali based pretreatment alone. Lignin dissolution was low for both methods under the conditions studied.

  • 18.
    Jakobsen, Trygve Dagsloth
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Paso, Kristofer
    NTNU Norwegian University of Science and Technology, Norway.
    Interactions between surfactants and cellulose nanofibrils for enhanced oil recovery2018In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, no 46, p. 15749-15758Article in journal (Refereed)
    Abstract [en]

    Chemical enhanced oil recovery (EOR) represents a series of potential solutions for extracting more oil from resources with already known locations and magnitudes. Unfortunately, many of the chemical additives in use today are not environmentally friendly. In the study a "greener" alternative for increasing viscosity of the injection water is investigated, namely cellulose nanofibrils (CNF). The nanofibrils are combined in systems with anionic sulfonate surfactants, SDBS and AOT, in order to decrease interfacial tension (IFT) between oil and water. In combination, the increase of water viscosity and decrease of IFT should result in higher ultimate oil recovery than if only conventional water flooding was applied. Interactions between cellulose nanofibrils and the surfactants have been investigated through adsorption studies, rheology, and IFT measurements. An observed synergy effect between CNF and surfactants upon viscosity of injection water, as well as with substantial decrease in IFT, leads the authors to the conclusion that an EOR system consisting of CNF and sulfonate surfactants has good potential for future applications.

  • 19.
    Michel, Bastien
    et al.
    Univeristy Grenoble Alpes, France.
    Bras, Julien
    Univeristy Grenoble Alpes, France.
    Dufresne, Alain
    Univeristy Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU, France.
    Production and mechanical characterisation of TEMPO-oxidised cellulose nanofibrils/β-cyclodextrin films and cryogels2020In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 25, no 10, article id 2381Article in journal (Refereed)
    Abstract [en]

    Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties for biomedical applications such as drug delivery and tissue engineering. In this work, we report the modification with β-cyclodextrin (βCD) of toCNF samples with different carboxyl contents viz. 756 ± 4 μmol/g and 1048 ± 32 μmol/g. The modification was carried out at neutral and acidic pH (2.5) to study the effect of dissociation of the carboxylic acid group. Films processed by casting/evaporation at 40 °C and cryogels processed by freeze-drying were prepared from βCD modified toCNF suspensions and compared with reference samples of unmodified toCNF. The impact of modification on water sorption and mechanical properties was assessed. It was shown that the water sorption behaviour for films is driven by adsorption, with a clear impact of the chemical makeup of the fibres (charge content, pH, and adsorption of cyclodextrin). Modified toCNF cryogels (acidic pH and addition of cyclodextrins) displayed lower mechanical properties linked to the modification of the cell wall porosity structure. Esterification between βCD and toCNF under acidic conditions was performed by freeze-drying, and such cryogels exhibited a lower decrease in mechanical properties in the swollen state. These results are promising for the development of scaffold and films with controlled mechanical properties and added value due to the ability of cyclodextrin to form an inclusion complex with active principle ingredient (API) or growth factor (GF) for biomedical applications. © 2020 by the authors.

  • 20.
    Michel, Bastien
    et al.
    Université Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Sillard, Cecile
    Université Grenoble Alpes, France.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU, Norway.
    Dufresne, Alain
    Université Grenoble Alpes, France.
    Bras, Julien
    Université Grenoble Alpes, France.
    Drug release and antimicrobial property of Cellulose Nanofibril/β-Cyclodextrin/Sulfadiazine films2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Active Principal Ingredient (API) encapsulation through adsorption and physical entrapment onto TEMPO-oxidized cellulose nanofibrils (toCNFs) is possible, but challenges such as burst release and use of low water-soluble API such as sulfadiazine (SD) are yet to be addressed. The objective of this study is to assess the release property and antibacterial activity of toCNF/β-Cyclodextrin (β-CD)/SD materials in the form of films. Release in sink conditions was achieved with result highlighting the importance of the toCNF network structure, which is tightened at acidic pH for toCNFs due to its carboxylic content, reducing the burst effect phenomena. Antibacterial activity against Staphylococcus aureus and Escherichia coli was assessed and the results showed a clear beneficial impact of using β-CDs. An antibacterial effect for toCNF/SD films is confirmed for 3 successive applications whereas an antibacterial effect for a toCNF/CMβCD/SD film is prolonged up to 7 successive applications. The improvement of the topical release of a prophylactic agent with these materials are making them promising for biomedical applications such as wound dressing. Graphic abstract: [Figure not available: see fulltext.] © 2023, The Author(s)

  • 21.
    Michel, Bastien
    et al.
    University Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU, Norway.
    Dufresne, Alain
    University Grenoble Alpes, France.
    Bras, Julien
    University Grenoble Alpes, France.
    Inclusion complex formation between sulfadiazine and various modified β-cyclodextrins and characterization of the complexes2022In: Journal of Drug Delivery Science and Technology, ISSN 1773-2247, Vol. 76, article id 103814Article in journal (Refereed)
    Abstract [en]

    β-Cyclodextrin (β-CD) and its derivatives are cyclic oligosaccharides which present the ability to form inclusion complexes with hydrophobic molecules and can bring new functionalities to a wide range of materials. As of today, the most used prophylactic drugs for wound dressing applications are sulfadiazine (SD) and its derivatives silver sulfadiazine (SSD). These drugs are used to prevent infections of the wounds; however, their low intrinsic water-solubility is a hindrance to their use. In this study, the inclusion complex formation between SD/SSD and the various β-CDs were assessed with various protocols. Isothermal Titration Calorimetry (ITC) experiments led to the conclusion that the formation constants measured for SD and SSD are sufficiently similar meaning that SD can be considered as a satisfactory model molecule. Phase Solubility Diagram (PSD) were built for SD and the various β-CDs, highlighting a 1:1 stoichiometry of inclusion and a linear increase in solubility of SD with increasing concentration of β-CDs- The formation constant ranged from 197 M−1 to 245 M−1 for the different β-CDs. X-Ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) experiments revealed the different physico-chemical properties affected by the formation of an inclusion complex. Finally, Nuclear Magnetic Resonance (NMR) experiments confirmed the depth of penetration of SD inside the β-CDs cavity as well as the orientation of SD, highlighting the fact that CM-β-CDs induce a deeper penetration than other β-CDs.

  • 22.
    Michel, Bastien
    et al.
    University Grenoble Alpes, France.
    Imberty, Anne
    University Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU, Norway.
    Bras, Julien
    University Grenoble Alpes, France.
    Dufresne, Alain
    University Grenoble Alpes, France.
    Adsorption characterization of various modified β-cyclodextrins onto TEMPO-oxidized cellulose nanofibril membranes and cryogels2021In: Sustainable Chemistry and Pharmacy, ISSN 2352-5541, Vol. 24, article id 100523Article in journal (Refereed)
    Abstract [en]

    TEMPO-Oxidized cellulose nanofibrils (toCNF), in the form of highly entangled network such as membrane or cryogels, have proven to be of interest for various applications, including drug release or purification by pollutant adsorption. β-Cyclodextrins (β-CDs) have the ability to form inclusion complexes with large amount of hydrophobic molecules, and are considered as a promising way to bring new functionalities to these materials, by reducing drug burst release effect or improving the pollutant adsorption properties. The study of the adsorption β-CDs onto toCNF is then crucial to design toCNF/β-CDs materials, but is very complex due to the chemical proximity between these compounds. In this study, we develop toCNF cryogels containing various types of β-CDs derivatives by physical adsorption. Different protocols for analyzing the interactions between these compounds, such as Isothermal Titration Calorimetry (ITC), Quartz-Crystal Microbalance with dissipation monitoring (QCM-d) and a Phenolphthalein-based protocol (PhP protocol) have been performed. Adsorption between β-CD and toCNF was proven at two different temperatures with ITC. QCM-d measurements allowed measuring adsorption of different β-CDs derivatives onto toCNF, with higher adsorption measured for the modified β-CDs, and with estimated binding capacity ranging from 13.4 to 47.6 μmol/g toCNF. PhP protocol allowed us to monitor the amount of β-CDs released in aqueous environment, highlighting a lower release for modified β-CDs onto toCNF, and the results were consistent with the estimated binding capacity. This quantification of the binding adsorption capacity of various β-CDs is key results for optimizing the design of toCNF/β-CDs materials.

  • 23.
    Rashad, Ahmad
    et al.
    University of Bergen, norway.
    Grøndahl, Martha
    NTNU, Norway.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Mustafa, Kamal
    University of Bergen, Norway.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. NTNU, Norway.
    Responses of Rat Mesenchymal Stromal Cells to Nanocellulose with Different Functional Groups2023In: ACS Applied Bio Materials, E-ISSN 2576-6422, Vol. 6, no 3, p. 987-998Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) are multiscale hydrophilic biocompatible polysaccharide materials derived from wood and plants. TEMPO-mediated oxidation of CNFs (TO-CNF) turns some of the primary hydroxyl groups to carboxylate and aldehyde groups. Unlike carboxylic functional groups, there is little or no information about the biological role of the aldehyde groups on the surface of wood-based CNFs. In this work, we replaced the aldehyde groups in the TO-CNF samples with carboxyl groups by another oxidation treatment (TO-O-CNF) or with primary alcohols with terminal hydroxyl groups by a reduction reaction (TO-R-CNF). Rat mesenchymal stem/stromal cells (MSCs) derived from bone marrow were seeded on polystyrene tissue culture plates (TCP) coated with CNFs with and without aldehyde groups. TCP and TCP coated with bacterial nanocellulose (BNC) were used as control groups. Protein adsorption measurements demonstrated that more proteins were adsorbed from cell culture media on all CNF surfaces compared to BNC. Live/dead and lactate dehydrogenase assays confirmed that all nanocellulose biomaterials supported excellent cell viability. Interestingly, TO-R-CNF samples, which have no aldehyde groups, showed better cell spreading than BNC and comparable results to TCP. Unlike TO-O-CNF surfaces, which have no aldehyde groups either, TO-R-CNF stimulated cells, in osteogenic medium, to have higher alkaline phosphatase activity and to form more biomineralization than TCP and TO-CNF groups. These findings indicate that the presence of aldehyde groups (280 ± 14 μmol/g) on the surface of TEMPO-oxidized CNFs might have little or no effect on attachment, proliferation, and osteogenic differentiation of MSCs. © 2023 The Authors.

  • 24.
    Rashad, Ahmad
    et al.
    University of Bergen, Norway.
    Mohamed-Ahmed, Samih
    University of Bergen, Norway.
    Ojansivu, Miina
    University of Bergen, Norway; University of Tampere, Finland.
    Berstad, Kaia
    University of Bergen, Norway.
    Yassin, Mohammad
    University of Bergen, Norway.
    Kivijärvi, Tove
    KTH Royal Institute of Technology, Sweden.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Coating 3D Printed Polycaprolactone Scaffolds with Nanocellulose Promotes Growth and Differentiation of Mesenchymal Stem Cells2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 11, p. 4307-4319Article in journal (Refereed)
    Abstract [en]

    3D printed polycaprolactone (PCL) has potential as a scaffold for bone tissue engineering, but the hydrophobic surface may hinder optimal cell responses. The surface properties can be improved by coating the scaffold with cellulose nanofibrils material (CNF), a multiscale hydrophilic biocompatible biomaterial derived from wood. In this study, human bone marrow-derived mesenchymal stem cells were cultured on tissue culture plates (TCP) and 3D printed PCL scaffolds coated with CNF. Cellular responses to the surfaces (viability, attachment, proliferation, and osteogenic differentiation) were documented. CNF significantly enhanced the hydrophilic properties of PCL scaffolds and promoted protein adsorption. Live/dead staining and lactate dehydrogenase release assays confirmed that CNF did not inhibit cellular viability. The CNF between the 3D printed PCL strands and pores acted as a hydrophilic barrier, enhancing cell seeding efficiency, and proliferation. CNF supported the formation of a well-organized actin cytoskeleton and cellular production of vinculin protein on the surfaces of TCP and PCL scaffolds. Moreover, CNF-coated surfaces enhanced not only alkaline phosphatase activity, but also collagen Type-I and mineral formation. It is concluded that CNF coating enhances cell attachment, proliferation, and osteogenic differentiation and has the potential to improve the performance of 3D printed PCL scaffolds for bone tissue engineering.

  • 25.
    Rashad, Amad
    et al.
    University of Bergen, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Cytocompatibility of Wood-Derived Cellulose Nanofibril Hydrogels with Different Surface Chemistry2017In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 18, no 4, p. 1238-1248Article in journal (Refereed)
    Abstract [en]

    The current study aims to demonstrate the influence of the surface chemistry of wood-derived cellulose nanofibril (CNF) hydrogels on fibroblasts for tissue engineering applications. TEMPO-mediated oxidation or carboxymethylation pretreatments were employed to produce hydrogels with different surface chemistry. This study demonstrates the following: first, the gelation of CNF with cell culture medium and formation of stable hydrogels with improved rheological properties; second, the response of mouse fibroblasts cultured on the surface of the hydrogels or sandwiched within the materials with respect to cytotoxicity, cell attachment, proliferation, morphology, and migration. Indirect cytotoxicity tests showed no toxic effect of either hydrogel. The direct contact with the carboxymethylated hydrogel adversely influenced the morphology of the cells and limited their spreading, while typical morphology and spreading of cells were observed with the TEMPO-oxidized hydrogel. The porous fibrous structure may be a key to cell proliferation and migration in the hydrogels.

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