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Surface modification of cellulose materials: from wood pulps to artificial blood vessels
KTH, School of Biotechnology (BIO).
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis describes the improvement of two radically different cellulose materials, paper and artificial blood vessels, constructed from two diverse cellulose sources, wood pulp and Acetobacter xylinum. The improvement of both materials was possible due to the natural affinity of the hemicellulose xyloglucan for cellulose.

Chemical and mechanical pulps were treated with xyloglucan in the wet-end prior to hand sheet formation or by spray application of dry hand sheets, loading a comparable amount of xyloglucan. The tensile strength increases for the wet-end treatment and spray application were 28% and 71% respectively for bleached soft wood, compared to untreated sheets (20.7 Nm/g). The corresponding strength increases for hand sheets made of thermo-mechanical pulp were 6% and 13% respectively compared to untreated sheets (42.4 Nm/g). The tendency for chemical pulp to be superior to mechanical pulp with respect to strength increase was valid even for tear strength and Scott-Bond. These results suggest, in agreement with other studies, that adhesion of xyloglucan to wood fibres is dependent on their degree of surface lignification.

Also, a method was developed to increase the blood compatibility of artificial blood vessels constructed of bacterial cellulose. Xyloglucan was covalently linked to the endothelial cell adhesion motif (Arg-Gly-Asp). To obtain this, new solid-phase coupling chemistry was developed. Xyloglucan oligosaccharides (XGO) were transformed into XGO-succinamic acid via the corresponding XGO--NH2 derivative prior to coupling with the N-terminus of the solid-phase synthesised Gly-Arg-Gly-Asp-Ser peptide. The resin-bound glyco-peptide was then cleaved and enzymatically re-incorporated into high molecular weight xyloglucan. The glyco-peptide was further adsorbed onto bacterial cellulose scaffolds, increasing the adhesion and proliferation of endothelial cells and therefore blood compatibility.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , 49 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2007:6
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-4437ISBN: 978-91-7178-680-7 (print)OAI: oai:DiVA.org:kth-4437DiVA: diva2:12307
Presentation
2007-06-08, FA 32, KTH, AlbaNova, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101102Available from: 2007-06-15 Created: 2007-06-15 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Paper dry strength improvement by xyloglucan addition: Wet-end application, spray coating and synergism with borate
Open this publication in new window or tab >>Paper dry strength improvement by xyloglucan addition: Wet-end application, spray coating and synergism with borate
2008 (English)In: Holzforschung, ISSN 0018-3830, Vol. 62, no 1, 8-14 p.Article in journal (Refereed) Published
Abstract [en]

The polysaccharide xyloglucan as a wet-end additive improves paper properties. In the present study, paper strength improvement was analysed for dry handsheets made from chemical, mechanical and recycled pulps coated with xyloglucan in a spray application. Results are compared with sheets made from the same pulps treated with xyloglucan in the wet-end. Kraft pulp handsheets of bleached hardwood and softwood showed significant improvements of tensile, tear and Z-strength by xyloglucan spray treatment versus wet-end application, whereas handsheets of de-inked and thermomechanical pulp were improved only slightly. In both wet-end and spray applications, the effect of xyloglucan addition was intimately related to the presence of non-cellulosic components on the fibre surface. Further strength improvements were obtained for chemical pulps by addition of borax to the spray solution, which were likely to be due to the formation of borate-mediated xyloglucan cross-links. Spray coating of xyloglucan, with or without borax, thus represents a potential new application of this polysaccharide to increase paper dry strength.

Keyword
borax, cellulose, cross-link, de-inked pulp, hardwood pulp, paper dry strength, softwood pulp, spray coating, thermomechanical pulp, xyloglucan
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:kth:diva-7326 (URN)10.1515/HF.2008.002 (DOI)000252041400002 ()2-s2.0-36849065266 (Scopus ID)
Note
Tidigare titel: Paper dry strength improvement by xyloglucan addition is critically dependent on the purity of cellulose fibre surfaces wet end application, spray coating and synergism with borate. Uppdaterad från submitted till published: 20101102. QC 20101102Available from: 2007-06-15 Created: 2007-06-15 Last updated: 2011-02-22Bibliographically approved
2. Modification of nanocellulose with a xyloglucan-RGD conjugate enhances adhesion and proliferation of endothelial cells: Implications for tissue engineering
Open this publication in new window or tab >>Modification of nanocellulose with a xyloglucan-RGD conjugate enhances adhesion and proliferation of endothelial cells: Implications for tissue engineering
Show others...
2007 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 12, 3697-3704 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a novel method for introducing the RGD cell adhesion peptide to enhance cell adhesion onto bacterial cellulose (BC). BC and cotton linters as reference were modified with xyloglucan (XG) and xyloglugan bearing a GRGDS pentapeptide. The adsorptions followed Langmuir adsorption behavior, where both XGs probably decorate the cellulose surfaces as a monolayer. The adsorption maximum of the XGs reached around 180 mg/g on BC and only about three times as much on cotton linters. The adsorption was verified with colorimetric methods. The specific surface area of BC measured with XG and XG-GRGDS was about 200 m(2)/g and was almost three times less for cotton linters, 60 m2/g. The difference in the amounts of XGs adsorbed might be explained by the swollen network of bacterial cellulose and a more exposed and accessible bulk as compared to cotton linters. The nanocellulose material was modified homogeneously throughout the material, as seen by the z-scan in confocal microscopy. Moreover, the modification in the water phase, in comparison with organic solvents, was clearly advantageous for preserving the morphology, as observed with SEM. The modification slightly increased the wettability, which might explain the decrease in or undetectable adsorption of adhesive protein shown by QCM-D. Initial cell studies showed that adhesion of human endothelial cells is enhanced when the BC hydrogel is modified with XG-GRGDS. QCM-D studies further revealed that the cell enhancement is due to the presence of the RGD epitope on XG and not to a nonspecific adsorption of fibronectin from cell culture medium. Optimization and proliferation studies of human endothelial cells onto bacterial cellulose modified with XG-GRGDS are currently being carried out at the Vascular Engineering Center, Sahlgrenska University Hospital, Gothenburg.

Keyword
Adsorption, Cell adhesion, Endothelial cells, Hydrogels, Morphology, Peptides
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-7327 (URN)10.1021/bm070343q (DOI)000251547600003 ()2-s2.0-38049034346 (Scopus ID)
Note
QC 20100923. Uppdaterad från Submitted till Published (20100923).Available from: 2007-06-15 Created: 2007-06-15 Last updated: 2010-11-02Bibliographically approved

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