| 1. |
- Arino Marine, Ruth, 1980, et al.
(författare)
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Thermal and viscoelastic properties of cellulosic gels with different ionic liquids and coagulation agents
- 2013
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Ingår i: BioResources. - 1930-2126 .- 1930-2126. ; 8:2, s. 2209-2221
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Tidskriftsartikel (refereegranskat)abstract
- Thermal and viscoelastic properties of three-component gels consisting of microcrystalline cellulose, ionic liquid, and coagulation agent were studied. The amount and type of components was varied to obtain different gel properties. The absorption of coagulation agent (13 to 35 %wt of water or ethanol) was found to depend on the types of ionic liquid and cellulose. Surface hydrophobization of cellulose prior to preparation of the gel remarkably resulted in the gels containing the most coagulation agent (35%wt). Rheological studies indicated a linear viscoelastic behavior in storage modulus but not in loss modulus, which is a behavior that, according to our knowledge, has not been seen before for gels. Increasing the cellulose concentration from 1:20 to 1:10 increased the stiffness of the gels. The highest critical stress value (1050 Pa) was obtained for a gel containing 1-butyl-3-methylimidazolium chloride and water. Finally, it was confirmed by dynamic-mechanical experiments that the gels had a cross-linked structure.
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| 2. |
- Bylin, Susanne, 1982, et al.
(författare)
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Solvation behavior of cellulose and xylan in the MIM/EMIMAc ionic liquid solvent system – parameters for small scale solvation
- 2014
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 9:1, s. 1038-1054
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquid treatment has been reported by several researchers as a possible step in the process of fractionating lignocellulosic biomass within the biorefinery concept. However, understanding how solvation can be achieved and how the feedstock biopolymers are affected is needed prior to a viable implementation. An effective two component solvent system for the wood components cellulose and xylan has been developed. Furthermore, the solvation of these components in the system consisting of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIMAc) in a novel combination with the co-solvent 1-methylimidazole (MIM) is investigated. Focused beam reflectance measurement (FBRM) particle characterization in combination with microscopic analysis and molecular weight determinations (xylan) shows that cellulose and xylan can be most efficiently solvated using only 3 to 4% IL (n/n anhydro-glucose units and n/n anhydro-xylose units) and 9% IL, respectively, while still avoiding any significant polymer degradation. A model for a two-step process of cellulose solvation in the present system is proposed.
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| 3. |
- de la Motte, Hanna, 1983, et al.
(författare)
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Molecular characterization of hydrolyzed cationized nanocrystalline cellulose, cotton cellulose and softwood kraft pulp using high resolution 1D and 2D NMR
- 2011
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 85:4, s. 738-746
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline cellulose, cotton linters and softwood kraft pulp were reacted with the cationic epoxide 2,3-epoxypropyltrimethyl ammonium chloride (EPTMAC) according to two different procedures, whereof one was a solvent and reagent minimizing spray technique. The samples were subjected to acid hydrolysis and characterized by solution-state nuclear magnetic resonance (NMR). The spectra were obtained using a 600 MHz cryoprobe NMR instrument. The use of ion exchange SPE-column chromatography enhanced the intensity of the peaks derived from the modified monosaccharide residues and opened for detailed NMR characterization at low degrees of substitution. In addition to a consistent 9 ppm change in the initial shifts of carbons adjacent to substituted hydroxyl groups, the NMR spectra proved that other neighboring atoms were affected by the substitution. Unlike nanocrystalline cellulose and cotton cellulose, the softwood kraft pulp cationized with the spray technique demonstrated a higher preference for 0-6 (83%), on the expense of O-2 substitution (16%).
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| 4. |
- de la Motte, Hanna, 1983, et al.
(författare)
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Regioselective cationization of cellulosic materials using an efficient solvent-minimizing spray-technique
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:5, s. 1677-1688
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Tidskriftsartikel (refereegranskat)abstract
- Cationization of different cellulosic materials was successfully accomplished using an efficient solvent-minimizing spray-technique. The obtained materials were studied and evaluated in regard to reaction efficiency and regioselectivity using 1D and H-1-C-13 correlated 2D NMR experiments. The high consistencies and temperatures applied using the spray-technique resulted in reagent effective etherifications and shorter reaction times. The NMR spectra indicated that the spray-technique favors substitutions at position O-6, showing a regioselectivity of O-6 > O-2 > O-3 for softwood kraft pulp (SKP) and cotton linters. However, cationization of mercerized cellulose and dissolving pulp, using the spray-technique, demonstrated more efficient reactions compared to SKP and cotton, and a regioselectivity of O-6 a parts per thousand yen O-2 > O-3. Nanocrystalline cellulose showed the lowest reactivity and a regioselectivity of O-6 a parts per thousand
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| 5. |
- Fryknäs, Mårten, et al.
(författare)
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Screening for phenotype selective activity in multidrug resistant cells identifies a novel tubulin active agent insensitive to common forms of cancer drug resistance
- 2013
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Ingår i: BMC Cancer. - : Springer Science and Business Media LLC. - 1471-2407 .- 1471-2407. ; 13, s. 374-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Drug resistance is a common cause of treatment failure in cancer patients and encompasses a multitude of different mechanisms. The aim of the present study was to identify drugs effective on multidrug resistant cells. Methods: The RPMI 8226 myeloma cell line and its multidrug resistant subline 8226/Dox40 was screened for cytotoxicity in response to 3,000 chemically diverse compounds using a fluorometric cytotoxicity assay (FMCA). Follow-up profiling was subsequently performed using various cellular and biochemical assays. Results: One compound, designated VLX40, demonstrated a higher activity against 8226/Dox40 cells compared to its parental counterpart. VLX40 induced delayed cell death with apoptotic features. Mechanistic exploration was performed using gene expression analysis of drug exposed tumor cells to generate a drug-specific signature. Strong connections to tubulin inhibitors and microtubule cytoskeleton were retrieved. The mechanistic hypothesis of VLX40 acting as a tubulin inhibitor was confirmed by direct measurements of interaction with tubulin polymerization using a biochemical assay and supported by demonstration of G2/M cell cycle arrest. When tested against a broad panel of primary cultures of patient tumor cells (PCPTC) representing different forms of leukemia and solid tumors, VLX40 displayed high activity against both myeloid and lymphoid leukemias in contrast to the reference compound vincristine to which myeloid blast cells are often insensitive. Significant in vivo activity was confirmed in myeloid U-937 cells implanted subcutaneously in mice using the hollow fiber model. Conclusions: The results indicate that VLX40 may be a useful prototype for development of novel tubulin active agents that are insensitive to common mechanisms of cancer drug resistance.
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| 6. |
- Gullbo, Joachim, et al.
(författare)
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Phenotype-based drug screening in primary ovarian carcinoma cultures identifies intracellular iron depletion as a promising strategy for cancer treatment
- 2011
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Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952 .- 1356-1839 .- 1873-2968. ; 82:2, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- Primary cultures of patient tumor cells (PCPTC) have been used for prediction of diagnosis-specific activity and individual patient response to anticancer drugs, but have not been utilized as a model for identification of novel drugs in high throughput screening. In the present study, ovarian carcinoma cells from three patients were tested in response to a library of 3000 chemically diverse compounds. Eight hits were retrieved after counter screening using normal epithelial cells, and one of the two structurally related hit compounds was selected for further preclinical evaluation. This compound, designated VLX 50, demonstrated a broad spectrum of activity when tested in a panel of PCPTCs representing different forms of leukemia and solid tumors and displayed a high tumor to normal cell activity. VLX 50 induced delayed cell death with some features of classical apoptosis. Significant in vivo activity was confirmed on primary cultures of human ovarian carcinoma cells in mice using the hollow fiber model. Mechanistic exploration was performed using gene expression analysis of drug exposed tumor cells to generate a drug-specific signature. This query signature was analyzed using the Gene Set Enrichment Analysis and the Connectivity Map database. Strong connections to hypoxia inducible factor 1 and iron chelators were retrieved. The mechanistic hypothesis of intracellular iron depletion leading to hypoxia signaling was confirmed by a series of experiments. The results indicate the feasibility of using PCPTC for cancer drug screening and that intracellular iron depletion could be a potentially important strategy for cancer therapy.
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| 7. |
- Hasani, Merima, 1978, et al.
(författare)
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Nano-cellulosic materials: The impact of water on their dissolution in DMAc/LiCl
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 98:2, s. 1565-1572
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution behaviour of disassociated cellulosic materials in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) was investigated. The parameters monitored were chromatographic elution profiles and recovered mass by means of gel permeation chromatography (GPC) with RI detection. In order to elucidate the impact of the disassembly on cellulosic fibres, comparative studies were performed with the non-disassociated cellulose counterparts. The importance of the presence of water was addressed by Karl Fischer titration and solvent exchange experiments. Morphological changes during the dissolution process were studied by scanning electron microscopy (SEM). Dissolution of fibrillated cellulosic materials is impeded compared to the non-fibrillated material. This is a consequence of the high-surface-area fibrils prone to retain high amounts of water. Dissolution behaviour of nano-crystalline cellulosic materials appeared to be source-dependent. Due to the absence of entangled networks, these materials retain only water bound at the surface of the nano-crystallites, indicative of both the exposed surface area and solubility. The small cellulose nano-particles extracted from dissolving pulp show lower solubility compared to the large NCC particles from cotton.
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| 8. |
- Hasani, Merima, 1978, et al.
(författare)
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Self-crosslinking of 2-hydroxypropyl-N-methylmorpholinium chloride cellulose fibres
- 2011
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 18:3, s. 575-583
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Tidskriftsartikel (refereegranskat)abstract
- Crosslinking of cellulose fibres was obtained by inducing a substitution reaction in a cationic cellulose ether (NMM-cellulose) prepared by action of N-oxiranylmethyl-N-methylmorpholinium chloride. During the reaction the N-methylmorpholine moiety of the cellulosic ether acts as a leaving group facilitating a covalent bond formation between the ether substituent and a hydroxyl or other nucleophilic group present in the cellulose chain. In order to provide additional evidence of the suggested crosslinking route and investigate its possibilities, different reaction conditions have been investigated and assessed in terms of the obtained fibre properties. The crosslinked fibres were characterized by means of elemental analysis and structure accessibility studies, including accessibility to water, anions and nitrogen gas. According to these investigations heating at 105 A degrees C induces a significant crosslinking. Pre-treatment with acetone restricts it mainly to formation of intra-fibre crosslinks, whereas heating from water suppresses the reactivity but results nevertheless in highly crosslinked structure with both intra- and inter-fibre crosslinks involved.
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| 9. |
- Henniges, U., et al.
(författare)
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Electron Beam Irradiation of Cellulosic Materials-Opportunities and Limitations
- 2013
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 6:5, s. 1584-1598
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Tidskriftsartikel (refereegranskat)abstract
- The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification.
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| 10. |
- Härdelin, Linda, 1977, et al.
(författare)
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Electrospinning of cellulose nanofibers from ionic liquids: The effect of different cosolvents
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 125:3, s. 1901-1909
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose was electrospun with various concentrations of ionic liquid and cosolvent. Three different cosolvents were used in this study; dimethylacetamide (DMAc), dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO). The cosolvents were added to modify the viscosity, electrical conductivity, and surface tension of the solutions. The solubility of cellulose in ionic liquids is highly affected by changes in solvent properties on the molecular level in the binary solvent systems. The difference in molecular structure of the cosolvents and the interactions between cosolvent and ionic liquid can explain the difference in dissolution power of the cosolvents. Scanning electron microscope (SEM) was used to characterize electrospun cellulose fibers. For the systems tested the importance of having a rather high viscosity and high surface tension, and some degree of shear thinning to produce fibers is shown.
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