| 1. |
- Escalante, Alfredo, 1975, et al.
(författare)
-
Flexible oxygen barrier films from spruce xylan
- 2012
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 87:4, s. 2381-2387
-
Tidskriftsartikel (refereegranskat)abstract
- Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-alpha-D-GlcpA at O-2 and of alpha-L-Araf at O-3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780 g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55 MPa, strain at break of 2.7% and a Young's Modulus 2735 MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.
|
|
| 2. |
- Farahani, Saina Kishani, et al.
(författare)
-
Experimental and Theoretical Evaluation of the Solubility/Insolubility of Spruce Xylan (Arabino Glucuronoxylan)
- 2019
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1263-1270
-
Tidskriftsartikel (refereegranskat)abstract
- © 2019 American Chemical Society. The molecular solubility of softwood arabinoglucuronoxylan (AGX) has been thoroughly investigated, and it has been shown that the chemical and physical structures of the extracted hemicellulose are not significantly influenced by different purification steps, but a transient molecular solubility of AGX was observed in aqueous media at low concentrations (1 g/L) when the dissolved macromolecules had a hydrodynamic diameter of up to 10 nm. A phase separation was detected when the concentration was increased to 15 g/L leading to an association of the smaller molecules into fractal structures with a considerably larger diameter, even though the dispersions were still transparent to ocular inspection. Dynamic Light Scattering and Cryo-Transmission Electron Microscopy showed dimensions in the range of 1000 nm. The phase separation of the sample was further characterized by estimating the χ-interaction parameter of AGX in water using the Flory-Huggins theory, and the results supported that water is a poor solvent for AGX. This behavior is crucial when films and hydrogels based on these biopolymers are made, since the association will dramatically affect barrier and mechanical properties of films made from these materials.
|
|
| 3. |
- Gutiérrez-Hernández, José Manuel, et al.
(författare)
-
In vitro evaluation of osteoblastic cells on bacterial cellulose modified with multi-walled carbon nanotubes as scaffold for bone regeneration
- 2017
-
Ingår i: Materials Science and Engineering C. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 75, s. 445-453
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we explore the use of native bacterial cellulose (BC) in combination with functionalized multi-walled carbon nanotubes (MWNTs) as an original biomaterial, suitable three-dimensional (3D) scaffold for osteoblastic cell culture. Functionalized MWNTs were mixed with native BC (secreted by Gluconacetobacter xylinus) with the aim of reinforcing the mechanical properties of BC. The results indicate that BC-MWNTs scaffolds support osteoblast viability, adhesion and proliferation at higher levels as compared to traditional culture substrates. Chemically functionalized MWNTs are also an excellent material to be used as scaffold because these did not affect cell viability and showed an enhanced osteoblast adhesion. These results suggest the potential for this combination of biomaterials, i.e. BC and carbon nanomaterials, as scaffolds for bone regeneration.
|
|
| 4. |
- Markstedt, Kajsa, 1989, et al.
(författare)
-
Biomimetic Inks Based on Cellulose Nanofibrils and Cross-Linkable Xylans for 3D Printing
- 2017
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:46, s. 40878-40886
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a sustainable all-wood-based ink which can be used for 3D printing of constructs for a large variety of applications such as clothes, furniture, electronics, and health care products with a customized design and versatile gel properties. The 3D printing technologies where the material is dispensed in the form of liquids, so called inks, have proven suitable for 3D printing dispersions of cellulose nanofibrils (CNFs) because of their unique shear thinning properties. In this study, novel inks were developed with a biomimetic approach where the structural properties of cellulose and the cross-linking function of hemicelluloses that are found in the plant cell wall were utilized. The CNF was mixed with xylan, a hemicellulose extracted from spruce, to introduce cross-linking properties which are essential for the final stability of the printed ink. For xylan to be cross-linkable, it was functionalized with tyramine at different degrees. Evaluation of different ink compositions by rheology measurements and 3D printing tests showed that the degree of tyramine substitution and the ratio of CNFs to xylan-tyramine in the prepared inks influenced the printability and cross-linking density. Both two-layered gridded structures and more complex 3D constructs were printed. Similarly to conventional composites, the interactions between the components and their miscibility are important for the stability of the printed and cross-linked ink. Thus, the influence of tyramine on the adsorption of xylan to cellulose was studied with a quartz crystal microbalance to verify that the functionalization had little influence on xylan's adsorption to cellulose. Utilizing xylan-tyramine in the CNF dispersions resulted in all-wood-based inks which after 3D printing can be cross-linked to form freestanding gels while at the same time, the excellent printing properties of CNFs remain intact.
|
|
| 5. |
- Toriz Gonzalez, Guillermo, 1968, et al.
(författare)
-
Xylan-lignin hydrogels
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
