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Hellwig, Johannes
Publications (7 of 7) Show all publications
Herrera, A., Hellwig, J., Leemhuis, H., von Klitzing, R., Heschel, I., Duda, G. N. & Petersen, A. (2019). From macroscopic mechanics to cell-effective stiffness within highly aligned macroporous collagen scaffolds. Materials science & engineering. C, biomimetic materials, sensors and systems, 103, Article ID 109760.
Open this publication in new window or tab >>From macroscopic mechanics to cell-effective stiffness within highly aligned macroporous collagen scaffolds
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2019 (English)In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 103, article id 109760Article in journal (Refereed) Published
Abstract [en]

In the design of macroporous biomaterial scaffolds, attention is payed predominantly to the readily accessible macroscopic mechanical properties rather than to the mechanical properties experienced by the cells adhering to the material. However, the direct cell mechanical environment has been shown to be of special relevance for biological processes such as proliferation, differentiation and extracellular matrix formation both in vitro and in vivo. In this study we investigated how individual architectural features of highly aligned macroporous collagen scaffolds contribute to its mechanical properties on the macroscopic vs. the microscopic scale. Scaffolds were produced by controlled freezing and freeze-drying, a method frequently used for manufacturing of macroporous biomaterials. The individual architectural features of the biomaterial were carefully characterized to develop a finite element model (FE-model) that finally provided insights in the relation between the biomaterial's mechanical properties on the macro-scale and the properties on the micro-scale, as experienced by adhering cells. FE-models were validated by experimental characterization of the scaffolds, both on the macroscopic and the microscopic level, using mechanical compression testing and atomic force microscopy. As a result, a so-called cell-effective stiffness of these non-trivial scaffold architectures could be predicted for the first time. A linear dependency between the macroscopic scaffold stiffness and the cell-effective stiffness was found, with the latter being consistently higher by a factor of 6.4 +/- 0.6. The relevance of the cell-effective stiffness in controlling progenitor cell differentiation was confirmed in vitro. The obtained information about the cell-effective stiffness is of particular relevance for the early stages of tissue regeneration, when the cells first populate and interact with the biomaterial. Beyond the specific biomaterial investigated here, the introduced method is transferable to other complex biomaterial architectures. Design-optimization in 3D macroporous scaffolds that are based on a deeper understanding of the mechanical environment provided to the cells will help to enhance biomaterial-based tissue regeneration approaches.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Cell-effective stiffness, Mechanobiology, Mechanical characterization, Scaffold architecture, FEM, Mesenchymal stromal cell differentiation
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-257795 (URN)10.1016/j.msec.2019.109760 (DOI)000480664900028 ()31349443 (PubMedID)2-s2.0-85066011841 (Scopus ID)
Note

QC 20190913

Available from: 2019-09-13 Created: 2019-09-13 Last updated: 2019-09-13Bibliographically approved
Karlsson, R.-M. P., Larsson, P. T., Yu, S., Pendergraph, S. A., Pettersson, T., Hellwig, J. & Wågberg, L. (2018). Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers. Journal of Colloid and Interface Science, 519, 119-129
Open this publication in new window or tab >>Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers
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2018 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed) Published
Abstract [en]

Macroscopic beads of water-based gels consisting of uncharged and partially charged beta-(1,4)-D-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling.

Place, publisher, year, edition, pages
Academic Press, 2018
Keywords
Swelling, Water uptake, Hydrogel, Cellulose, Small-angle X-ray scattering, Solid state NMR, Atomic force microscopy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-226733 (URN)10.1016/j.jcis.2018.02.052 (DOI)000429633500013 ()29486431 (PubMedID)2-s2.0-85042413398 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180503

Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2019-04-25Bibliographically approved
López Durán, V., Hellwig, J., Larsson, P. A. & Wågberg, L. (2018). Effect of Chemical Functionality on the Mechanical and Barrier Performance of Nanocellulose Films. ACS APPLIED NANO MATERIALS, 1(4), 1959-1967
Open this publication in new window or tab >>Effect of Chemical Functionality on the Mechanical and Barrier Performance of Nanocellulose Films
2018 (English)In: ACS APPLIED NANO MATERIALS, ISSN 2574-0970, Vol. 1, no 4, p. 1959-1967Article in journal (Refereed) Published
Abstract [en]

In the present work, we have partially modified fibrils chemically to eate a shell of derivatized cellulose that surrounds the crystalline re of native cellulose. Through the different modifications, we aimed creating a toolbox to enable the properties of CNF materials and terials containing CNFs to be tuned to meet specific material demands. total, nine different chemical modifications using different ueous-based procedures were used as chemical pretreatments before CNF oduction through homogenization. Eight of these modifications included riodate oxidation with an average of 27% of the anhydroglucose units the cellulose chain being cleaved into dialdehydes. The presence of dehydes then facilitated a conversion to other functional groups.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
borohydride reduction, chemical modification, chlorite oxidation, ductility, nanocellulose, periodate oxidation, reductive amination, TEMPO oxidation
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-248115 (URN)10.1021/acsanm.8b00452 (DOI)000461400500061 ()
Note

QC 20190426

Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-11-14Bibliographically approved
Hellwig, J., López Durán, V. & Pettersson, T. (2018). Measuring elasticity of wet cellulose fibres with AFM using indentation and a linearized Hertz model. Analytical Methods, 10(31)
Open this publication in new window or tab >>Measuring elasticity of wet cellulose fibres with AFM using indentation and a linearized Hertz model
2018 (English)In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 10, no 31Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of different pulp fibres in liquid were measured using an atomic force microscope. Specifically a custom-made sample holder was used to indent the fibre surface, without causing any motion, and the Young's modulus was calculated from the indentation using a linearized Hertz model.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-234605 (URN)10.1039/c8ay00816g (DOI)000442260600001 ()2-s2.0-85051472152 (Scopus ID)
Funder
VinnovaWallenberg Foundations
Note

QC 20180914

Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2019-11-14Bibliographically approved
Pettersson, T., Hellwig, J., Gustafsson, P.-J. & Stenstrom, S. (2017). Measurement of the flexibility of wet cellulose fibres using atomic force microscopy. Cellulose (London), 24(10), 4139-4149
Open this publication in new window or tab >>Measurement of the flexibility of wet cellulose fibres using atomic force microscopy
2017 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 10, p. 4139-4149Article in journal (Refereed) Published
Abstract [en]

Flexibility and modulus of elasticity data for two types of wet cellulose fibres using a direct force-displacement method by means of AFM are reported for never dried wet fibres immersed in water. The flexibilities for the bleached softwood kraft pulp (BSW) fibres are in the range of 4-38 x 10(12) N-1 m(-2) while the flexibilities for the thermomechanical pulp (TMP) fibres are about one order of magnitude lower. For BSW the modulus of elasticity ranges from 1 to 12 MPa and for TMP between 15-190 MPa. These data are lower than most other available pulp fibre data and comparable to a soft rubber band. Reasons for the difference can be that our measurements with a direct method were performed using never dried fibres immersed in water while other groups have employed indirect methods using pulp with different treatments.

Place, publisher, year, edition, pages
SPRINGER, 2017
Keywords
Flexibility, Modulus of elasticity, AFM, Cellulose fibre
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-215440 (URN)10.1007/s10570-017-1407-6 (DOI)000410759600003 ()2-s2.0-85025442559 (Scopus ID)
Note

QC 20171019

Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2017-10-19Bibliographically approved
Hellwig, J., Karlsson, R. M., Wågberg, L. & Pettersson, T. (2017). Measuring elasticity of wet cellulose beads with an AFM colloidal probe using a linearized DMT model. Analytical Methods, 9(27), 4019-4022
Open this publication in new window or tab >>Measuring elasticity of wet cellulose beads with an AFM colloidal probe using a linearized DMT model
2017 (English)In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 9, no 27, p. 4019-4022Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of wet cellulose are investigated using an atomic force microscope AFM and calculated using a linearized DMT model. Measurements were performed using a model system of gel beads made of cellulose with different charge densities, which show a high impact on the mechanical properties of the cellulose in wet state.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-215478 (URN)10.1039/c7ay01219e (DOI)000411460700001 ()2-s2.0-85023750517 (Scopus ID)
Note

QC 20171013

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2019-05-22Bibliographically approved
López Durán, V., Hellwig, J., Larsson, P. T., Wågberg, L. & Larsson, P. A.Effect of chemical functionality on the mechanical and barrier performance of all-cellulose composites.
Open this publication in new window or tab >>Effect of chemical functionality on the mechanical and barrier performance of all-cellulose composites
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-232099 (URN)
Note

QC 20180711

Available from: 2018-07-11 Created: 2018-07-11 Last updated: 2018-07-11Bibliographically approved
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