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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, Bioekonomi och hälsa, Material- och ytdesign.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. 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 eor2020Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 10, nr 7, artikkel-id 1296Artikkel i tidsskrift (Fagfellevurdert)
    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), Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, 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 media2018Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 8, nr 7, artikkel-id 547Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    fulltext
  • 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, Bioekonomi, 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, Bioekonomi, 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 recovery2019Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 9, nr 5, artikkel-id 665Artikkel i tidsskrift (Fagfellevurdert)
    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), Bioekonomi, PFI.
    Simon, Sébastien
    Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, PFI. Norwegian University of Science and Technology, Norway.
    Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils-The Effects of Ionic Strength and pH.2019Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 9, nr 2, artikkel-id E259Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Aaen, Ragnhild
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Lehtonen, Mari
    University of Helsinki, Finland.
    Mikkonen, Kirsi
    University of Helsinki, Finland.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU Norwegian University of Science and Technology, Norway.
    Combining cellulose nanofibrils and galactoglucomannans for enhanced stabilization of future food emulsions2021Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, nr 16, s. 10485-10500Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of wood-derived cellulose nanofibrils (CNFs) or galactoglucomannans (GGM) for emulsion stabilization may be a way to obtain new environmentally friendly emulsifiers. Both have previously been shown to act as emulsifiers, offering physical, and in the case of GGM, oxidative stability to the emulsions. Oil-in-water emulsions were prepared using highly charged (1352 ± 5 µmol/g) CNFs prepared by TEMPO-mediated oxidation, or a coarser commercial CNF, less charged (≈ 70 µmol/g) quality (Exilva forte), and the physical emulsion stability was evaluated by use of droplet size distributions, micrographs and visual appearance. The highly charged, finely fibrillated CNFs stabilized the emulsions more effectively than the coarser, lower charged CNFs, probably due to higher electrostatic repulsions between the fibrils, and a higher surface coverage of the oil droplets due to thinner fibrils. At a constant CNF/oil ratio, the lowest CNF and oil concentration of 0.01 wt % CNFs and 5 wt % oil gave the most stable emulsion, with good stability toward coalescence, but not towards creaming. GGM (0.5 or 1.0 wt %) stabilized emulsions (5 wt % oil) showed no creaming behavior, but a clear bimodal distribution with some destabilization over the storage time of 1 month. Combinations of CNFs and GGM for stabilization of emulsions with 5 wt % oil, provided good stability towards creaming and a slower emulsion destabilization than for GGM alone. GGM could also improve the stability towards oxidation by delaying the initiation of lipid oxidation. Use of CNFs and combinations of GGM and CNFs can thus be away to obtain stable emulsions, such as mayonnaise and beverage emulsions. © 2021, The Author(s).

  • 6.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    Norwegian University of Science and Technology, Norway.
    Wernersson Brodin, Fredrik
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. Norwegian University of Science and Technology, Norway.
    The potential of TEMPO-oxidized cellulose nanofibrils as rheology modifiers in food systems2019Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, nr 9, s. 5483-5496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: Cellulose nanofibrils (CNFs) have been proposed for use in low-fat food products due to their availability and excellent viscosifying and gel forming abilities. As the CNFs are negatively charged, the presence of other components in foods, such as electrolytes and food additives such as xanthan gum is likely to affect their rheological properties. Hence, the study of these interactions can contribute valuable information of the suitability of CNFs as rheology modifiers and fat replacers. Rheological measurements on aqueous dispersions of TEMPO-oxidized CNFs were performed with variations in concentration of CNFs, concentration of electrolytes and with varying CNF/xanthan ratios. UV–Vis Spectroscopy was used to evaluate the onset of CNF flocculation/aggregation in the presence of electrolytes. The CNF dispersions followed a power-law dependency for viscosity and moduli on CNF concentration. Low electrolyte additions strengthened the CNF network by allowing for stronger interactions, while higher additions led to fibril aggregation, and loss of viscosity, especially under shear. The CNF/xanthan ratio, as well as the presence of electrolytes were shown to be key factors in determining whether the viscosity and storage modulus of CNF dispersions increased or decreased when xanthan was added. Graphical abstract: [Figure not available: see fulltext.].

  • 7.
    Aarstad, Olav
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, 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), Bioekonomi, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils2017Inngår i: Polymers, E-ISSN 2073-4360, Vol. 9, nr 8, artikkel-id 378Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    fulltext
  • 8. Alexandrescu, L.
    et al.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Iotti, M.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Gregersen, Ø.
    Belosi, F.
    Gatti, A.M.
    Air filtration of nano-particles using cellulose nanofibrils2012Konferansepaper (Fagfellevurdert)
  • 9.
    Alexandrescu, Laura C.
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Gatti, Antonietta Maria
    ISTEC-CNR, Italy.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Cytotoxicity tests of cellulose nanofibril-based structures2013Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, nr 4, s. 1765-1775Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibrils based on wood pulp fibres are most promising for biomedical applications. Bacterial cellulose has been suggested for some medical applications and is presently used as wound dressing. However, cost-efficient processes for mass production of bacterial cellulose are lacking. Hence, fibrillation of cellulose wood fibres is most interesting, as the cellulose nanofibrils can efficiently be produced in large quantities. However, the utilization of cellulose nanofibrils from wood requires a thorough verification of its biocompatibility, especially with fibroblast cells which are important in regenerative tissue and particularly in wound healing. The cellulose nanofibril structures used in this study were based on Eucalyptus and Pinus radiata pulp fibres. The nanofibrillated materials were manufactured using a homogenizer without pre-treatment and with 2,2,6,6-tetramethylpiperidine-1-oxy radical as pre-treatment, thus yielding nanofibrils low and high level of anionic charge, respectively. From these materials, two types of nanofibril-based structures were formed; (1) thin and dense structures and (2) open and porous structures. Cytotoxicity tests were applied on the samples, which demonstrated that the nanofibrils do not exert acute toxic phenomena on the tested fibroblast cells (3T3 cells). The cell membrane, cell mitochondrial activity and the DNA proliferation remained unchanged during the tests, which involved direct and indirect contact between the nano-structured materials and the 3T3 cells. Some samples were modified using the crosslinking agent polyethyleneimine (PEI) or the surfactant cetyl trimethylammonium bromide (CTAB). The sample modified with CTAB showed a clear toxic behaviour, having negative effects on cell survival, viability and proliferation. CTAB is an antimicrobial component, and thus this result was as expected. The sample crosslinked with PEI also had a significant reduction in cell viability indicating a reduction in DNA proliferation. We conclude that the neat cellulose nanostructured materials tested in this study are not toxic against fibroblasts cells. This is most important as nano-structured materials based on nanofibrils from wood pulp fibres are promising as substrate for regenerative medicine and wound healing.

  • 10.
    Bardet, Raphael
    et al.
    Université Grenoble Alpes, France; CNRS, France.
    Reverdy, Charlène
    Université Grenoble Alpes, France; CNRS, France.
    Belgacem, Naceur
    Université Grenoble Alpes, France; CNRS, France.
    Leirset, Ingebjørg
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Bardet, Michel
    Université Grenoble Alpes, France; CEA, France.
    Bras, Julien
    Université Grenoble Alpes, France; CNRS, France.
    Substitution of nanoclay in high gas barrier films of cellulose nanofibrils with cellulose nanocrystals and thermal treatment2015Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 2, s. 1227-1241Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study is to design a nanocellulose based barrier film. For this purpose, cellulose nanofibrils (CNFs) are used as a matrix to create an entangled nanoporous network that is filled with two different nanofillers: nanoclay (reference), i.e. the mineral montmorillonite (MMT) and the bio-based TEMPO-oxidized cellulose nanocrystal (CNC-T), to produce different types of nanocelluloses and their main physical and chemical features were assessed. As expected, films based on neat CNFs exhibit good mechanical performance and excellent barrier properties at low moisture content. The introduction of 32.5 wt% of either nanofiller results in a significant improvement of barrier properties at high moisture content. Finally, thermal treatment of a dried CNF/CNC-T film results in a decrease of the oxygen permeability even at high moisture content (>70 %). This is mainly attributed to the hornification of nanocellulose. A key result of this study is that the oxygen permeability of an all-nanocellulose film in 85 % relative humidity (RH), is similar to CNF film with mineral nanoclay (MMT), i.e. 2.1 instead of 1.7 cm3 µm m−2 day−1 kPa−1, respectively.

  • 11.
    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, Bioekonomi och hälsa, Material- och ytdesign.
    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, Bioekonomi och hälsa, Material- och ytdesign. 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 behavior2020Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 10, nr 6, artikkel-id 1219Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 12.
    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, Bioekonomi, 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, Bioekonomi, 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 nanofibrils2019Inngår i: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 94, s. 867-878Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 13.
    Carlström, Ingeborg
    et al.
    University of Bergen, Norway.
    Rashad, Ahmad
    University of Bergen, Norway.
    Campodoni, Elisabetta
    National Research Council of Italy, Italy.
    Sandri, Monica
    National Research Council of Italy, Italy.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Bolstad, Anne
    University of Bergen, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Cross-linked gelatin-nanocellulose scaffolds for bone tissue engineering2020Inngår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 264, artikkel-id 127326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood-based cellulose nanofibrils (CNFs) have, in addition to high specific surface area and high surface reactivity, ability to mimic nanostructured collagen in bone extracellular matrix. These properties make CNFs promising materials for bone tissue engineering (BTE). The CNFs degrade slowly in vivo. By blending and cross-linking gelatin (Gel) with CNFs, scaffolds were produced with tuned degradation rate and enhanced mechanical properties, more suitable for BTE applications. This in vitro study aimed to examine initial biological responses of human bone marrow mesenchymal stem cells to cross-linked Gel-CNF scaffolds. The scaffolds were fabricated from 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF blended with Gel and cross-linked either by dehydrothermal treatment (DHT) or by a combination of hexamethylenediamine, genipin, and DHT. CNF scaffolds without cross-linking served as control. The produced scaffolds supported cell attachment, spreading, and osteogenic differentiation. However, the early cell attachment after 1 day and the expression of RUNX2 and SPP1 genes after 7 days were highest in the CNF scaffolds. The results suggest that cross-linked Gel-CNF are cytocompatible and holds potential for BTE applications. 

  • 14.
    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, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Iovu, Horia
    University Politehnica of Bucharest, Romania; Academy of Romanian Scientists, Romania.
    Bioinspired 3D printable pectin-nanocellulose ink formulations2019Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 220, s. 12-21Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 15.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Kirsebom, H.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Designing nanocellulose qualities for wound dressings2013Konferansepaper (Fagfellevurdert)
  • 16.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Powell, L.C
    Cardiff University School of Dentistry, UK; Swansea University, UK.
    Nordli, H.R
    NTNU Norwegian University of Science and Technology, Norway.
    Khan, S
    Cardiff University, UK.
    Hill, K.E
    Cardiff University, UK.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Thomas, D.W
    Cardiff University, UK.
    Nanocellulose from wood as a biomaterial for biomedical applications2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the last decades major efforts have been made to produce nanocellulose from wood, where the cellulose fibres are disintegrated into individualized nanofibrils with diameters < 20 nm and lengths in the micrometre scale. Production procedures include various pre-treatments, which yield nanocelluloses with varying chemical and structural properties. One important area of research is nanocellulose as a biomaterial with potential applications within the health sector. As an example, the superior mechanical properties, good moisture retention capability and the ability to form elastic macro-porous structures are advantageous properties for utilizing nanocellulose substrates for wound dressings. However, the utilization of nanocellulose as a substrate for wound dressings requires a thorough assessment of the biocompatibility of the material.  In this respect, it has been demonstrated in-vitro that nanocellulose does not exert acute toxic phenomena on fibroblast cells. However, in addition to in-vitro cytotoxicity testing, in-vivo testing of nanocellulose and the ability of nanocellulose to resist bacterial colonization need a closer attention. This presentation will give an overview of the current research on nanocellulose as a biomaterial for wound dressing applications, considering the morphology of nanocellulose structures, mechanical properties, moisture absorption, cytotoxicity tests and nanocellulose-bacteria interactions.

  • 17.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Cellulose nanofibrils: production, characterization and applications2011Inngår i: Fine Structure of Papermaking Fibres, Swedish University of Agricultural Sciences , 2011, , s. 13Kapittel i bok, del av antologi (Fagfellevurdert)
  • 18.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    On the porosity and oxygen barrier properties of cellulose nanofibril-based films2011Konferansepaper (Fagfellevurdert)
  • 19.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    On the structure and oxygen transmission rate of biodegradable cellulose nanobarriers2012Inngår i: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 7Artikkel i tidsskrift (Fagfellevurdert)
  • 20.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels2014Inngår i: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 3, nr 29, s. 423-432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms.

    Fulltekst (pdf)
    fulltext
  • 21.
    Djafari Petroudy, Seyed Rahman
    et al.
    Shahid Beheshti University, Iran.
    Ghasemian, Ali
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Resalati, Hossein
    Sari University of Agricultural Sciences and Natural Resources, Iran.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    The effect of xylan on the fibrillation efficiency of DED bleached soda bagasse pulp and on nanopaper characteristics2015Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 1, s. 385-395Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Xylan is the second most abundant polysaccharide and the most abundant hemicellulose component of soda bagasse pulp. In this study, bleached soda bagasse pulp (SB) and bleached bagasse dissolving pulp (DB) with varying amounts of xylan were fibrillated with a homogenization process. The produced fibrillated materials were used for making nanopaper structures. The surface, physical, mechanical and optical properties of the nanopaper were measured, and the effect of xylan was assessed. Laser profilometry (LP) and field emission scanning electron microscopy were applied to study the degree of the fibrillation. The pulp having the highest xylan content, SB, showed the highest yield of cellulose nanofibrils. Nanopaper produced from SB had a more consolidated structure than that produced from DB. Additionally, SB nanopaper yielded higher tensile strength, lower LP roughness, a higher barrier against oxygen and lower opacity. These results indicate a higher degree of fibrillation of the SB pulp compared to the DB pulp. Hence, the positive effect of xylan for facilitating the fibrillation of the starting pulp fibers was demonstrated.

  • 22.
    Djafari Petroudy, Seyed Rahman
    et al.
    NTNU Norwegian University of Science and Technology, Norway; Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Ghasemain, Ali
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Resalati, Hossein
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Effects of bagasse microfibrillated cellulose and cationic polyacrylamide on key properties of bagasse paper2014Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 99, s. 311-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study explores the benefits of using bagasse microfibrillated cellulose (MFC) in bagasse paper. Two different types of MFC were produced from DED bleached soda bagasse pulp. The MFC was added to soda bagasse pulp furnishes in different amounts. Cationic polyacrylamide (C-PAM) was selected as retention aid. The results show that addition of MFC increased the strength of paper as expected. Interestingly, 1% MFC in combination with 0.1% C-PAM yielded similar drainage time as the reference pulp, which did not contain MFC. In addition, the samples containing 1% MFC and 0.1% C-PAM yielded (i) a significant increment of the tensile index, (ii) a minor decrease of opacity and (iii) preserved Gurley porosity. Hence, this study proves that small fractions of MFC in combination with adequate retention aids can have positive effects with respect to paper properties, which is most interesting from an industrial point of view.

  • 23. Djafari Petroudy, S.R.
    et al.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Ghasemain, A.
    Resalati, H.
    Gregersen, Ø.W.
    Oriented nanopaper (ONP) made of bagasse nanofibrils2012Konferansepaper (Fagfellevurdert)
  • 24.
    El Miri, N.
    et al.
    Mid Sweden University, Sweden.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Wallsten, Sara
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Svedberg, Anna
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Norgren, Magnus
    Mid Sweden University, Sweden.
    A comprehensive investigation on modified cellulose nanocrystals and their films properties2022Inngår i: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 219, s. 998-1008Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 25.
    Fall, Andreas
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Henriksson, Marielle
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Karppinen, A.
    Borregaard, Norway.
    Opstad, A.
    Borregaard, Norway.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    The effect of ionic strength and pH on the dewatering rate of cellulose nanofibril dispersions2022Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 29, nr 14, s. 7649-7662Artikkel i tidsskrift (Fagfellevurdert)
    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.].

  • 26.
    Heggset, Ellinor B
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Aaen, Ragnhild
    NTNU Norwegian University of Science and Technology, Norway.
    Veslum, Trinelise
    Mills AS, Norway.
    Henriksson, Marielle
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU Norwegian University of Science and Technology, Norway.
    Cellulose nanofibrils as rheology modifier in mayonnaise – A pilot scale demonstration2020Inngår i: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 108, artikkel-id 106084Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 27.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Temperature stability of nanocellulose dispersions2017Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 157, s. 114-121Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 28.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi, 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, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, 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 gels2019Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, nr 1, s. 581-595Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29. 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 treatment2016Inngår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 93, s. 194-200Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 30.
    Helberg, Ragne
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Torstensen, Jonathan
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Dai, Zhongde
    NTNU Norwegian University of Science and Technology, Norway.
    Janakiram, Saravanan
    NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Gregersen, Øyvind
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU Norwegian University of Science and Technology, Norway.
    Deng, Liyuan
    NTNU Norwegian University of Science and Technology, Norway.
    Nanocomposite membranes with high-charge and size-screened phosphorylated nanocellulose fibrils for CO2 separation2021Inngår i: Green Energy and Environment, ISSN 2096-2797, Vol. 6, nr 4, s. 585-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, cellulose nanofibrils (CNF) of high charge (H-P-CNF) and screened size (H-P-CNF-S) were fabricated by increasing the charge of phosphorylated cellulose nanofibrils (P-CNFs) during the pre-treatment step of CNF production. Results show that the H-P-CNF have a significantly higher charge (3.41 mmol g−1) compared with P-CNF (1.86 mmol g−1). Centrifugation of H-P-CNF gave a supernatant with higher charge (5.4 mmol g−1) and a reduced size (H-P-CNF-S). These tailored nanocelluloses were added to polyvinyl alcohol (PVA) solutions and the suspensions were successfully coated on porous polysulfone (PSf) supports to produce thin-film nanocomposite membranes. The humid mixed gas permeation tests show that CO2 permeability increases for membranes with the addition of H-P-CNF-S by 52% and 160%, compared with the P-CNF/PVA membrane and neat PVA membrane, respectively. 

  • 31.
    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, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, 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 recovery2018Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, nr 46, s. 15749-15758Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 32.
    Kumar, Vinay
    et al.
    Åbo Akademi University, Finland.
    Ottesen, Vegar
    NTNU, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Gregersen, Öyvind Weiby
    NTNU, Norway.
    Toivakka, Martti
    Åba Akademi University, Finland.
    Coatability of cellulose nanofibril suspensions: Role of rheology and water retention2017Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, nr 4, s. 7656-7679Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibril (CNF) suspensions are not easily coatable because of their excessively high viscosity and yield stress, even at low solids concentrations. In addition, CNF suspensions vary widely in their properties depending on the production process used, which can affect their processability. This work reports roll-to-roll coating of three different types of CNF suspensions with a slot-die, and the influence of rheology and water retention on coatability is addressed. The impact of CMC addition on the high and low shear rate rheology, water retention, coatability, and final coating quality of these suspensions is reported. All three CNF suspensions were coated successfully using the slot-die coating process. CMC addition further improved the coatability by positively influencing both the low and high shear rate viscosity and water retention of the CNF suspensions. All CNF coatings significantly improved the air, heptane vapor, grease and oil barrier, while reducing the water vapor transmission rate to some extent.

    Fulltekst (pdf)
    fulltext
  • 33.
    Larsson, Per Tomas
    et al.
    RISE., Innventia.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Wohlert, Jakob
    KTH Royal Institute of Technology, Sweden.
    Bergenstråhle, Malin
    KTH Royal Institute of Technology, Sweden.
    Changes in the supra-molecular structure of cellulose I during TEMPO-oxidation: bringing together NMR, MD and XRD results2016Inngår i: The 7th Workshop on cellulose, regenerated cellulose and cellulose derivatives, 2016, s. 35-35, artikkel-id 9Konferansepaper (Annet vitenskapelig)
  • 34.
    Liu, Jun
    et al.
    Åbo Akademi University, Finland.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Cheng, Fang
    Åbo Akademi University, Finland; University of Turku, Finland.
    Xu, Wenyang
    Åbo Akademi University, Finland.
    Willför, Stefan
    Åbo Akademi University, Finland.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Xu, Chunlin
    Åbo Akademi University, Finland.
    Hemicellulose-reinforced nanocellulose hydrogels for wound healing application2016Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, nr 5, s. 3129-3143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polysaccharides are finding an increasing number of applications in medical and pharmaceutical fields thanks to their biodegradability, biocompatibility, and in some cases bioactivity. Two approaches were applied to use hemicelluloses as crosslinkers to tune the structural and mechanical properties of nanofibrillated cellulose (NFC) hydrogel scaffolds, and thus to investigate the effect of these properties on the cellular behavior during wound healing application. Different types of hemicellulose (galactoglucomannan (GGM), xyloglucan (XG), and xylan) were introduced into the NFC network via pre-sorption (Method I) and in situ adsorption (Method II) to reinforce the NFC hydrogels. The charge density of the NFC, the incorporated hemicellulose type and amount, and the swelling time of the hydrogels were found to affect the pore structure, the mechanical strength, and thus the cells’ growth on the composite hydrogel scaffolds. The XG showed the highest adsorption capacity on the NFC, the highest reinforcement effect, and facilitated/promoted cell growth. The pre-sorbed XG in the low-charged NFC network with a lower weight ratio (NFC/XG-90:10) showed the highest efficacy in supporting the growth and proliferation of fibroblast cells (NIH 3T3). These all-polysaccharide composite hydrogels may work as promising scaffolds in wound healing applications to provide supporting networks and to promote cells adhesion, growth, and proliferation.

  • 35.
    Lungu, Adriana
    et al.
    University Politehnica of Bucharest, Romania.
    Cernencu, Alexandra
    University Politehnica of Bucharest, Romania.
    Dinescu, Sorina
    University of Bucharest, Romania.
    Balahura, Roxana
    University of Bucharest, Romania.
    Mereuta, Paul
    National Institute for Physics and Nuclear Engineering, Romania.
    Costache, Marieta
    University of Bucharest, Romania.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU Norwegian University of Science and Technology, Norway.
    Stancu, Izabela
    University Politehnica of Bucharest, Romania.
    Iovu, Horia
    Academy of Romanian Scientists, Romania; University Politehnica of Bucharest, Romania.
    Nanocellulose-enriched hydrocolloid-based hydrogels designed using a Ca2+ free strategy based on citric acid2021Inngår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 197, artikkel-id 109200Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work fully biomass-based hydrogels were developed using a naturally occurring vegetable hydrocolloid co-mingled with wood-derived nanocellulose fibrils. Two distinct types of hydrocolloids have been considered: a seaweed-derived biopolymer (alginate) and a plant-derived biopolymer (pectin). To attain nano-structured binary hydrogels, surface-functionalized cellulose nanofibrils (CNFs) bearing carboxyl groups were employed. This study addresses a non-conventional approach of physical gelation that takes place in acidic conditions (pH &lt; 3) at ambiental temperature using citric acid as gelation-inducing additive in comparison with the typical Ca2+-crosslinked hydrogels. The use of a specific crosslinker directly determines the gross properties of the material because of different type and density of polymer junctions and chains assembly. Therefore, the final features of the bioinspired scaffolds such as moisture uptake, morphological and mechanical characteristics are strongly influenced by the type of gelling additive used and by the ratio between the employed vegetal polysaccharides. Citric acid-based hydrogels presented a higher stability when compared to the calcium-mediated controls and a significantly higher proliferation was detected when raising the hydrocolloid content and when citric acid was used for crosslinking. The newly adopted crosslinking strategy provides a more cell-interactive microenvironment than calcium-based crosslinking leading to improved viability and cytoskeleton development of stem cells. 

  • 36.
    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, Bioekonomi och hälsa, Material- och ytdesign.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU, France.
    Production and mechanical characterisation of TEMPO-oxidised cellulose nanofibrils/β-cyclodextrin films and cryogels2020Inngår i: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 25, nr 10, artikkel-id 2381Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 37.
    Michel, Bastien
    et al.
    Université Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Sillard, Cecile
    Université Grenoble Alpes, France.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. 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 films2023Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882XArtikkel i tidsskrift (Fagfellevurdert)
    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)

  • 38.
    Michel, Bastien
    et al.
    University Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. 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 complexes2022Inngår i: Journal of Drug Delivery Science and Technology, ISSN 1773-2247, Vol. 76, artikkel-id 103814Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 39.
    Michel, Bastien
    et al.
    University Grenoble Alpes, France.
    Imberty, Anne
    University Grenoble Alpes, France.
    Heggset, Ellinor B
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. 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 cryogels2021Inngår i: Sustainable Chemistry and Pharmacy, ISSN 2352-5541, Vol. 24, artikkel-id 100523Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 40. Mikczinski, M.
    et al.
    Josefsson, G.
    Chinga-Carrasco, Gary
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Gamstedt, E.K.
    Fatikow, S.
    Introducing an in-situ microrobotic approach for assessing the stiffness properties of microfibrillated cellulose films2012Konferansepaper (Fagfellevurdert)
  • 41.
    Molnes, Silje N.
    et al.
    University of Stavanger, Norway; NTNU Norwegian University of Science and Technology, Norway.
    Mamonov, Aleksandr
    University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Strand, Skule
    University of Stavanger, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Investigation of a new application for cellulose nanocrystals: a study of the enhanced oil recovery potential by use of a green additive2018Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 4, s. 2289-2301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNC) were investigated for use in a potential new application, enhanced oil recovery. Core flooding experiments were performed on outcrop sandstone cores using CNC particles dispersed in low salinity brine (CNC-LS). Core flooding experiments performed on fully water-saturated cores confirm that a majority of viscosity-generating CNC particles successfully traverse the cores at temperature conditions ranging from 60 to 120 A degrees C. Oil recovery tests performed on crude oil saturated sandstone cores at 60 and 90 A degrees C show that when CNC-LS is applied in tertiary mode, ultimate oil recovery increases. During tertiary CNC-LS injection, CNC particles exacerbate differential pressure fluctuations, a phenomenon attributable to log jamming in pore throats, causing remobilisation of oil trapped within pore space regions. Results from the current work indicate that CNC particles dispersed in low saline brine remain promising for implementation in enhanced oil recovery operations.

  • 42.
    Molnes, Silje N.
    et al.
    NTNU Norwegian University of Science and Technology, Norway; University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Strand, Skule
    University of Stavanger, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU Norwegian University of Science and Technology, Norway.
    The effects of pH, time and temperature on the stability and viscosity of cellulose nanocrystal (CNC) dispersions: implications for use in enhanced oil recovery2017Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, nr 10, s. 4479-4491Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNC) are currently being investigated as potential additives for enhanced oil recovery (EOR). Presented in this paper is a study investigating the effects of different physical and chemical environments that low concentration CNC dispersions may be subjected to at oil reservoir conditions. Different concentrations of CNC dispersed in de-ionized water and in a 1000 ppm NaCl brine were subjected to variations in pH and temperature, and the results showed that the dispersions remained stable in the pH range expected in oil reservoirs (between 5 and 9). Stable dispersions were also observed when heated to temperatures ranging from 50 to 90 °C. At extended heat aging at 90 and 120 °C for seven days; beginning degradation was observed for both types of CNC dispersions; with viscosity increase and pH decrease as the most important indicators. CNC dispersed in 1000 ppm NaCl brine was generally more heat tolerant than the CNC dispersed in de-ionized water. The increase in viscosity during heat aging can be very interesting for EOR applications. A fluid that increases its viscosity with heat and time will be easier to inject due to a low initial viscosity, and when the viscosity increases in the porous reservoir, the effect can be a stable waterfront and less viscous fingering, which again can lead to increased sweep efficiency and better oil recovery.

  • 43.
    Molnes, Silje N.
    et al.
    UoS University of Stavanger, Norway; NTNU Norwegian University of Science and Technology, Norway.
    Torrijos, Ivan P.
    UoS University of Stavanger, Norway.
    Strand, Skule
    UoS University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Sandstone injectivity and salt stability of cellulose nanocrystals (CNC) dispersions: Premises for use of CNC in enhanced oil recovery2016Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 93, s. 152-160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reservoir production is frequently supported by using flooding fluids, often seawater. The efficiency is affected by various factors, such as the wettability of the reservoir rock and the mobility ratio between reservoir oil and injected fluid phase. These factors again influence sweep efficiency, which is the fraction of the total reservoir oil volume in contact with injected fluid during oil recovery. Addition of nanoparticles can affect the sweep efficiency on a macroscopic level by increasing the volume of petroleum in contact with the flooding fluid. Presented here are core-flooding studies performed using cellulose nanocrystals (CNC) of different concentrations in low-saline water. The studies were performed to investigate the injectivity of CNC into a high-permeable sandstone core, and to observe the effects addition of electrolytes had on the rheological properties of a low concentration dispersion of CNC. Zeta- potential and shear viscosity of dilute dispersions containing CNC was investigated under increasing electrolyte concentration. The flooding experiments show that the CNC has good injectivity in sandstone for all concentrations used, and the viscosity measurements performed on the effluent prove that the particles are able to travel through the core. Being sufficiently small for injection into sandstone and showing good colloidal stability at low salinities, CNC particles have the premises necessary to function properly as a flooding additive for enhanced oil recovery (EOR) in sandstone reservoirs.

  • 44.
    Ojansivu, Miina
    et al.
    Tampere University, Finland.
    Rashad, Ahmad
    University of Bergen, Norway.
    Ahlinder, Astrid Elisabet
    KTH Royal institute of technology, Sweden.
    Massera, Jonathan
    Tampere University, Finland.
    Mishra, Ayush
    Tampere University, Finland.
    Syverud, Kristin
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, PFI.
    Finne-Wistrand, Anna
    KTH Royal institute of technology, Sweden.
    Miettinen, Susanna
    Tampere University, Finland.
    Mustafa, Kamal
    University of Bergen, Norway.
    Wood-based nanocellulose and bioactive glass modified gelatin-alginate bioinks for 3D bioprinting of bone cells2019Inngår i: Biofabrication, ISSN 1758-5082, E-ISSN 1758-5090, Vol. 11, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A challenge in the extrusion-based bioprinting is to find a bioink with optimal biological and physicochemical properties. The aim of this study was to evaluate the influence of wood-based cellulose nanofibrils (CNF) and bioactive glass on the rheological properties of gelatin-alginate bioinks and the initial responses of bone cells embedded in these inks. CNF modulated the flow behavior of the hydrogels, thus improving their printability. Chemical characterization by SEM-EDX and ion release analysis confirmed the reactivity of the BaG in the hydrogels. The cytocompatibility of the hydrogels was shown to be good, as evidenced by the viability of human osteoblast-like cells (Saos-2) in cast hydrogels. For bioprinting, 4-layer structures were printed from cell-containing gels and crosslinked with CaCl2. Viability, proliferation and alkaline phosphatase activity (ALP) were monitored over 14 days. In the BaG-free gels, Saos-2 cells remained viable, but in the presence of BaG the viability and proliferation decreased in correlation with the increased viscosity. Still, there was a constant increase in the ALP activity in all the hydrogels. Further bioprinting experiments were conducted using human bone marrow-derived mesenchymal stem cells (hBMSCs), a clinically relevant cell type. Interestingly, hBMSCs tolerated the printing process better than Saos-2 cells and the ALP indicated BaG-stimulated early osteogenic commitment. The addition of CNF and BaG to gelatin-alginate bioinks hold great potential for bone tissue engineering applications.

  • 45.
    Ottesen, V
    et al.
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering.
    Gregersen,  Ø
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering;.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Nanocellulose in Paper and Packaging2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    One possible way to improve competitiveness of paper materials is through utilization of nanocellulose to achieve new properties or to reduce production cost. Several studies have shown that nanofibrillar cellulose (NFC) can act as strength enhancing additive in paper or for paper surface improvements. NFC has the potential to bind large amounts of inorganic fillers in the paper sheet, and by this reduce energy consumption during paper production considerably. However, there are challenges that need to be addressed before the novel concepts can be realized, e.g. impaired drainage and drying of paper resulting from addition of NFC. This may be solved by obtaining the right balance between NFC quality, chemicals and additives. Promising results in this respect have been obtained  but this is still in an early stage. Fiber-based packaging materials represent a “green” alternative to petroleum based packaging solutions. Depending on the packaging category, different properties are important. For the segment liquid packaging board, barrier against oxygen is important. Currently, this is obtained by using aluminum, or the petroleum-based polymer EVOH in combination with a water barrier. Replacing these materials with “green” alternatives would represent a large environmental achievement. While superior oxygen barrier properties has been demonstrated for NFC,  good barrier against water and oxygen requires the combination of nanofibrils with complementary materials. Adequate combinations with other materials and feasible application techniques are still challenges that need to be solved. Other packaging segments require other properties, e.g. high stiffness or fracture toughness. By development of appropriate nanocellulose qualities, such properties can be improved. By preparing fibrils with small diameter, translucent films can be prepared. This is an interesting property for food packaging, where transparency may be a desired trait.

  • 46.
    Ottesen, V
    et al.
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering.
    Gregersen,  Ø
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering;.
    Syverud, Kristin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Nanocellulose Properties of Interest for Paper and Packaging2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cellulose Nano-Fibrils (CNF) is a biocompatible nano-material with appealing mechanical and optical properties. The high specific surface area (SSA) of nanofibrils ensure that a large fraction of the polymer chains in each fibril are surface fibrils, meaning numerous surface hydroxyl groups will be available to form bonds between components in the paper, ensuring high density and strength. CNF may be added to conventional paper as a strengthening agent. CNF films may be used as a barrier coating, or CNF sheets may be used in a number of products due to their potential transparency, strength and barrier properties. As a paper additive, CNF as a nanomaterial acts as a material that increases density and form bonds between fibers in the paper, providing an increased strength and stiffness whereas dusting and permeability is reduced. For papers where strength is chiefly limited by inter-fiber bonding strength, increases in excess of 100 % may be achieved by addition of small amounts of CNF. Less, but still significant contributions can be seen for papers whose strength is less dependent on inter-fiber bonding strength. Due to the pore-blocking properties of CNF coupled with Cellulose’s hydrophilic properties, dewatering on the paper machine is a challenge when CNF is used in this fashion. The high density, viz. the low porosity and small pore size (~0.47 nm), of CNF films provide a significant reduction in mass-transport. Applying such a film to a less efficient barrier material, or producing a pure CNF film presents oxygen transfer rates comparable with the best synthetic polymer films produced for this purpose. Sheets of pure CNF or a CNF composite may transmit 90 % of incident light with a wavelength of 600 nm. This transparency is due to the high density and small fibril size in sheets of pure CNF or a CNF-based composite, which results in a lower scattering coefficient compared to corresponding conventional fiber based sheets. Transparent sheets such as these may be of interest in packaging applications where the packaged goods, such as foodstuffs or luxury articles, is desired displayed to the end customer. The properties of CNF, whether as a film, a paper additive or a major paper or composite component may be of significant industrial interest due to the unique properties of the material.

  • 47.
    Ottesen, Vegar
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Kumar, Vinay Santhosh
    Åbo Akademi University, Finland.
    Toivakka, Martti
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Chinga-Carrasco, Gary
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Weiby Gregersen, Öyvind
    NTNU Norwegian University of Science and Technology, Norway.
    Viability and properties of roll-to-roll coating of cellulose nanofibrils on recycled paperboard2017Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, nr 2, s. 179-188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibrils (CNF) are, due in large part to excellent gas barrier properties, a potential environmentally friendly alternative to inorganic and petrochemical coatings of e.g. paperboard in packaging applications. In the current paper successful roll-to-roll coating of three qualities of CNF is demonstrated on a recycled quality, porous paperboard using a custom-built pilot machine. Single layers of three different thicknesses were applied for each coating. The three CNF qualities used were carboxymethylated CNF (CNF-C), TEMPOoxidized CNF (CNF-T) and mechanically produced CNF without chemical pre-treatment (CNF-M). All three qualities, which have a range of surface charge, fibril size and fibril size distribution, are shown to produce films that adhere well to the base board. It is revealed that the coating is suspended across surface pores in the base board, as opposed to penetrate into the base board pore structure. Samples were investigated for air and water permeability, gloss, surface roughness and hole density in the coating. Chemically pretreated qualities outperform CNF-M. Addition of 5 wt% carboxy-methyl cellulose (CMC) was shown to reduce hole formation, improve gloss and reduce surface roughness. For thick applications of pre-treated CNF, in particular CNF-C, mechanical strength of the board in and out of the plane increase beyond the un-treated or water treated base board. Possibly a consequence of matter migrating through the base board from the CNF suspension.

  • 48.
    Ottesen, Vegar
    et al.
    NTNU, Norway.
    Larsson, Per Tomas
    KTH Royal Institute of Technology,´Sweden.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU, Norway.
    Gregersen, Öyvind
    NTNU, Norway.
    Mechanical properties of cellulose nanofibril films: effects of crystallinity and its modification by treatment with liquid anhydrous ammonia2019Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, nr 11, s. 6615-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of cellulose crystallinity on mechanical properties of cellulose nano-fibrils (CNF) was investigated. Degree of crystallinity (DoC) was modified using liquid anhydrous ammonia. Such treatment changes crystal allomorph from cellulose I to cellulose III, a change which was reversed by subsequent boiling in water. DoC was measured using solid state nuclear magnetic resonance (NMR). Crystalline index (CI) was also measured using wide angle X-ray scattering (WAXS). Cotton linters were used as the raw material. The cotton linter was ammonia treated prior to fibrillation. Reduced DoC is seen to associate with an increased yield point and decreased Young modulus. Young modulus is here defined as the maximal slope of the stress–strain curves. The association between DoC and Young modulus or DoC and yield point are both statistically significant. We cannot conclude there has been an effect on strainability. While mechanical properties were affected, we found no indication that ammonia treatment affected degree of fibrillation. CNF was also studied in air and liquid using atomic force microscopy (AFM). Swelling of the nanofibers was observed, with a mean diameter increase of 48.9%.

  • 49.
    Ottesen, Vegar
    et al.
    NTNU Norwegian university of science and technology, Norway.
    Roede, Erik Dobloug
    NTNU Norwegian university of science and technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioekonomi, PFI. NTNU Norwegian university of science and technology, Norway.
    Gregersen, Øyvind Weiby
    NTNU Norwegian university of science and technology, Norway.
    Focused ion beam tomography as a means for characterization of CNF in a paper matrix2017Inngår i: 16th Fundamental Research symposium, 2017, s. 595-609Konferansepaper (Fagfellevurdert)
  • 50.
    Ottesen, Vegar
    et al.
    NTNU, Norway.
    Syverud, Kristin
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign. NTNU, Norway.
    Swelling of individual cellulose nanofibrils in water, role of crystallinity: an AFM study2021Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, s. 19-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: Atomic force microscopy (AFM) can be used to quantitatively study nanomaterials in different media, e.g. vacuum, air, or submerged in a liquid.A technique was developed to study swelling of individual cellulose nanofibrils (CNFs) using AFM.As a case study, CNFs with different degrees of crystallinity (DoC) were examined for swellability going from dry to wet (submerged in de-ionized water). Swelling was found to depend on DoC, but no significant correlation between fibril diameter and swellability was seen. Upon introduction of de-ionized water high DoC samples (65 ± 2 %) were found to have a diameter increase of 34% on average, whereas low DoC (44 ± 2 %) were found to have a diameter increase of 44% on average. A tested control, consisting of platinum nanowires on silisium, did not swell. Graphic abstract: [Figure not available: see fulltext.] © 2020, The Author(s).

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