| 1. |
- Göhl, Johan, 1989, et al.
(författare)
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Simulations of 3D bioprinting : Predicting bioprintability of nanofibrillar inks
- 2018
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Ingår i: Biofabrication. - : IOP Publishing. - 1758-5082 .- 1758-5090. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- 3D bioprinting with cell containing bioinks show great promise in the biofabrication of patient specific tissue constructs. To fulfil the multiple requirements of a bioink, a wide range of materials and bioink composition are being developed and evaluated with regard to cell viability, mechanical performance and printability. It is essential that the printability and printing fidelity is not neglected since failure in printing the targeted architecture may be catastrophic for the survival of the cells and consequently the function of the printed tissue. However, experimental evaluation of bioinks printability is time-consuming and must be kept at a minimum, especially when 3D bioprinting with cells that are valuable and costly. This paper demonstrates how experimental evaluation could be complemented with computer based simulations to evaluate newly developed bioinks. Here, a computational fluid dynamics simulation tool was used to study the influence of different printing parameters and evaluate the predictability of the printing process. Based on data from oscillation frequency measurements of the evaluated bioinks, a full stress rheology model was used, where the viscoelastic behaviour of the material was captured. Simulation of the 3D bioprinting process is a powerful tool and will help in reducing the time and cost in the development and evaluation of bioinks. Moreover, it gives the opportunity to isolate parameters such as printing speed, nozzle height, flow rate and printing path to study their influence on the printing fidelity and the viscoelastic stresses within the bioink. The ability to study these features more extensively by simulating the printing process will result in a better understanding of what influences the viability of cells in 3D bioprinted tissue constructs.
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| 2. |
- Apelgren, Peter, et al.
(författare)
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Long-term in vivo integrity and safety of3D-bioprinted cartilaginous constructs
- 2021
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Ingår i: Journal of Biomedical Materials Research Part B-Applied Biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 109:1, s. 126-136
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Tidskriftsartikel (refereegranskat)abstract
- Long-term stability and biological safety are crucial for translation of 3D-bioprinting technology into clinical applications. Here, we addressed the long-term safety and stability issues associated with 3D-bioprinted constructs comprising a cellulose scaffold and human cells (chondrocytes and stem cells) over a period of 10 months in nude mice. Our findings showed that increasing unconfined compression strength over time significantly improved the mechanical stability of the cell-containing constructs relative to cell-free scaffolds. Additionally, the cell-free constructs exhibited a mean compressive stress and stiffness (compressive modulus) of 0.04 +/- 0.05 MPa and 0.14 +/- 0.18 MPa, respectively, whereas these values for the cell-containing constructs were 0.11 +/- 0.08 MPa (p= .019) and 0.53 +/- 0.59 MPa (p= .012), respectively. Moreover, histomorphologic analysis revealed that cartilage formed from the cell-containing constructs harbored an abundance of proliferating chondrocytes in clusters, and after 10 months, resembled native cartilage. Furthermore, extension of the experiment over the complete lifecycle of the animal model revealed no signs of ossification, fibrosis, necrosis, or implant-related tumor development in the 3D-bioprinted constructs. These findings confirm the in vivo biological safety and mechanical stability of 3D-bioprinted cartilaginous tissues and support their potential translation into clinical applications.
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| 3. |
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| 4. |
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| 5. |
- Håkansson, Karl, 1984, et al.
(författare)
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Solidification of 3D printed nanofibril hydrogels into functional 3D cellulose structures
- 2016
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Ingår i: Advanced Materials Technologies. - : Wiley. - 2365-709X. ; 1:7, s. 1600096-
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils isolated from trees have the potential to be used as raw material for future sustainable products within the areas of packaging, textiles, biomedical devices, and furniture. However, one unsolved problem has been to convert the nanofibril-hydrogel into a dry 3D structure. In this study, 3D printing is used to convert a cellulose nanofibril hydrogel into 3D structures with controlled architectures. Such structures collapse upon drying, but by using different drying processes the collapse can be controlled and the 3D structure can be preserved upon solidification. In addition, a conductive cellulose nanofibril ink is fabricated by adding carbon nanotubes. These findings enable the use of wood derived materials in 3D printing for fabrication of sustainable commodities such as packaging, textiles, biomedical devices, and furniture with conductive parts. Furthermore, with the introduction of biopolymers into 3D printing, the 3D printing technology itself can finally be regarded as sustainable.
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| 6. |
- Markstedt, Kajsa, 1989, et al.
(författare)
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3D Bioprinting Human Chondrocytes with Nanocellulose-Alginate Bioink for Cartilage Tissue Engineering Applications
- 2015
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:5, s. 1489-1496
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of 3D bioprinting is expected to revolutionize the field of tissue engineering and regenerative medicine. The 3D bioprinter is able to dispense materials while moving in X, Y, and Z directions, which enables the,engineering of complex Structures from the bottom up. In this study, a. bioink that combines, the outstanding Shear thinning properties Of nanofibrillated Cellulose (NFC) With the fast cross-linking ability Of alginate was formulated for the 3D bioprinting of living soft tissue with cells. Printability was evaluated with concern: to printer parameters and shape fidelity. The shear thinning behavior of the tested bioinks enabled printing of both 2D gridlike structures as well as 3D constructs. Furthermore, anatomically shaped cartilage structures, such as a human ear and sheep meniscus, were 3D printed using MRI and CT images as blueprints. Human chondrocytes bioprinted in the noncytotoxic, nanocellulose-based bioink exhibited a cell. viability of 73% and 86% after 1 and 7 days of 3D culture, respectively. On the basis of these results, we can conclude that the nanocellulose-based bioink is a suitable hydrogel for 3D bioprinting with living cells. This study demonstrates the potential use of nanocellulose for 3D bioprinting of living tissues and organs.
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| 7. |
- Markstedt, Kajsa, 1989, et al.
(författare)
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3D Bioprinting of Cellulose Structures from an Ionic Liquid
- 2014
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Ingår i: 3D Printing and Additive Manufacturing. - : Mary Ann Liebert Inc. - 2329-7662 .- 2329-7670. ; 1:3, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- This article reports on 3D bioprinting of dissolved cellulose to produce small feature structures with a tailored design ofregenerated cellulose. The process consists of dissolving cellulose with different origins and molecular weight in an ionic liquid(1 - ethyl - 3 - methylimidazolium acetate), controlled multilayered dispensing, and coagulation. The printability was examined bystudying the viscosity of cellulose solutions and by varying the settings of the printer setup regarding flow rate and needledimensions. Water was added as a nonsolvent, enabling a coagulation process to form a gel structure of the printed solutions.By printing on a coagulating gel, the printed solutions were regenerated within a few seconds. Rheology analysis showed thathigher concentrations of cellulose and cellulose of a high molecular weight were shear thinning, providing favorable printingproperties. Printing 3D structures of cellulose dissolved in an ionic liquid followed by coagulation by a nonsolvent was possible.Both complex patterns of 2D structures as well as multilayered prints were created to obtain 3D structures. This novel methodallows for the production of spatially tailored 3D gels or membrane structures made from cellulose.
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| 8. |
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| 9. |
- Markstedt, Kajsa, 1989
(författare)
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3D Printing Wood Tissue
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biomass from forests provides society with energy, materials and chemicals, thus contributing to the circular bioeconomy. The majority of biomass is found in the wood tissue of trees. Its composition and hierarchical structure originates from the synthesis and bottom-up assembly of biopolymers which involve numerous genes, hormones and exogenous factors. A technology for bottom-up fabrication of materials is 3D printing. In 3D printing, material is assembled layer-by-layer and thereby offers the potential to build up hierarchical complex structures with control of design and material properties. 3D printing wood is not as straight forward as for plastics since wood can’t be processed by melting. Also, printing wood involves the assembly of multiple polymers since wood is a composite material. Inspired by the composition, crosslinking mechanism, anisotropy and structural design of natural wood tissue, this work has established a platform for 3D printing wood biopolymers into hierarchical wood-like structures. The platform consists of extrusion-based 3D printers, designed printing pathways, and wood based solutions and dispersions which are called inks. We found that inks of both cellulose dissolved in ionic liquid and dispersions of cellulose nanofibrils (CNF) were printable due to their shear thinning properties. Good printing fidelity of cellulose solutions required a continuous gel formation. Printing on a coagulating gel allowed non-solvent to diffuse through the print and instantly regenerate cellulose. Diffusion through multiple layers was however challenging making it difficult to 3D print large constructs. CNF (1-4 wt%) exhibits a yield stress, and stops flowing when leaving the nozzle which facilitated the printing of multilayered structures, i.e. an ear. This also contributed to the printing resolution (≈ 300 μm). However, without crosslinking, the printed CNF could not withstand mechanical force. Hence, CNF was mixed with crosslinkable biopolymers. The mixed inks remained printable for CNF concentrations above 2 wt%. The crosslinking time was below 10 minutes and gel strength increased with the concentration of crosslinkable biopolymers. Inks containing alginate were ionically crosslinked and formed reversible hydrogels. Enzymatic crosslinking, similar to the polymerization of monolignols in the wood cell wall was obtained by substituting carboxylic groups (COOH) of hemicelluloses with tyramine. Hydrogels with tunable mechanical properties were obtained by varying the degree of substitution by using xylan, or TEMPO oxidized galactoglucomannan with degrees of oxidation from 10 to 60%. A computational fluid dynamics simulation tool was studied as a complement to 3D printing tests of new inks to evaluate printability. By simulation, it was easy to isolate parameters such as printing speed and printing height to study their influence on printing fidelity. Finally, natural bottom up assembly of wood tissue was substituted with 3D printing. G-code substituted genome and the cellulose was extruded by a printer head instead of the rosette. Structures that resemble morphological features found in wood were prepared by computer aided design and printed with all wood based inks. Control of printing paths provided anisotropic features resembling the micro fibril angle of the cell wall. The breakthrough of this work is the 3D shaping of wood by a bottom up process. Consequently, products assembled by wood biopolymers can transform from 2D (paper, board, films, textiles) to 3D. The concepts developed in this work can be employed in future applications of 3D printing with wood based materials, such as garments, electronics, wound dressings and packaging.
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| 10. |
- Markstedt, Kajsa, 1989, et al.
(författare)
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Biomimetic Inks Based on Cellulose Nanofibrils and Cross-Linkable Xylans for 3D Printing
- 2017
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:46, s. 40878-40886
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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.
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| 11. |
- Markstedt, Kajsa, 1989, et al.
(författare)
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Materials from trees assembled by 3D printing – Wood tissue beyond nature limits
- 2019
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Ingår i: Applied Materials Today. - : Elsevier BV. - 2352-9407. ; 15, s. 280-285
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Tidskriftsartikel (refereegranskat)abstract
- Materials from trees have the potential to replace fossil based and other non-sustainable materials in everyday products, thus transforming the society back to a bioeconomy. This paper presents a 3D printing platform which mimics wood biogenesis for the assembly of wood biopolymers into wood-like hierarchical composites. The genome was substituted with G-code, the programming language which controls how the 3D printer assembles material. The rosette was replaced by the printer head for extrusion of cellulose. Instead of microtubules guiding the alignment of cellulose, the printing direction was guided by an x/y stage, thus mimicking the microfibril angle. The printed structures were locked by an enzymatic crosslinking reaction similar to what occurs in the cell wall upon lignification. Hierarchical structures characteristic for wood were designed and printed with control of density, swelling and directional strength. Accelerating the development of the 3D printing technology helps realize the circular bioeconomy where garments, packaging, furniture and entire houses are manufactured by 3D printing wood.
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| 12. |
- Markstedt, Kajsa, 1989, et al.
(författare)
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Synthesis of tunable hydrogels based on O-acetyl-galactoglucomannans from spruce
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 157, s. 1349-1357
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Elsevier LtdHydrogels with tunable mechanical properties based on O-acetyl-galactoglucomannans (GGMs) from spruce functionalized with tyramine, a molecule containing crosslinkable phenolic groups, were prepared. Gel formation was induced by enzymatic crosslinking at the addition of horse radish peroxidase and hydrogen peroxide to the modified GGMs. The degree of substitution determined the hydrogels final properties, and was varied by TEMPO oxidation of GGM to a degree of oxidation from 10 to 60%. GGM and its derivatives were characterized by gas chromatography and high pressure size exclusion chromatography to analyze sugar composition and molar mass, respectively. Tyramine-conjugated GGM was evaluated by nuclear magnetic resonance, fourier transform infrared spectroscopy and elemental analysis. Measurements of moduli over time showed crosslinking within 20 s and maximum stress of the prepared gels were compared by compression testing. Overall this system presents a cell friendly hydrogel from a renewable, low cost resource which could be applied in cell delivery, wound dressings, and biofabrication.
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| 13. |
- Sundberg, Johan, 1982, et al.
(författare)
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3D Bioprinting of lignocellulosic materials with controlled micro architecture
- 2014
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Ingår i: Abstract of Papers of the American Chemical Society. - 0065-7727. ; 247
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wood derived biopolymers offer an environmentally friendly substitute to petroleum based synthetic polymers. Due to strong molecular interactions between wood biopolymers the dissolution and further processing is however challenging. Ionic liquids are powerful solvents that can be used to dissolve entire wood and fractionate it into wood biopolymers. Dissolution of cellulose and hemicelluloses is possible in ionic liquids such as 1-Ethyl-3-methylimidazolium acetate (EmimAc) and does not cause significant degradation of the polymer chains. We have showed that the dissolved cellulose and hemicelluloses can be regenerated into desired shape by coagulation. Using 3D Bioprinting process we were able to fabricate complex 3D structures from wood derived biopolymers dissolved in ionic liquid. A wide range of processing parameters has been optimized in order to achieve 3D structures with controlled micro architecture.
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| 14. |
- Säljö, Karin, 1981, et al.
(författare)
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Successful engraftment, vascularization, and In vivo survival of 3D-bioprinted human lipoaspirate-derived adipose tissue
- 2020
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Ingår i: Bioprinting. - : Elsevier BV. - 2405-8866. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Autologous fat grafting is commonly used for correction of soft-tissue deformities, despite a high rate of graft resorption and nutrition-supply challenges. Three-dimensional (3D)-bioprinting techniques enable tailor-made architecture of grafts and promote vascularization. In recent years, the importance of adipose tissue-derived stromal/stem cells (ASCs) for graft survival has become evident. This study investigated the printability of mechanically processed lipoaspirate containing ASCs, as well as in vivo survival and neovascularisation of the 3D-bioprinted grafts. Human lipoaspirate-derived adipose tissue was 3D bioprinted in alginate/nanocellulose bioink, implanted into nude mice, and harvested at days 3, 7, and 30, respectively. The processed lipoaspirate showed high viability and good printability when combined with alginate/nanocellulose, and the 3D-bioprinted grafts contained intact vascular structures and a high density of mature adipocytes before and after engraftment. After 30 days in vivo, novel blood vessels were present on the graft surface, showing signs of angiogenesis into the graft, as well as vascularization in the centre of the tissue. Moreover, histologic and immunohistochemical characterisation confirmed the presence of potential ASCs during the first week in vivo. These results demonstrated that human lipoaspirate-derived adipose tissue showed high printability, survived 3D bioprinting and engraftment in vivo, and displayed macroscopic and microscopic evidence of vascularization.
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| 15. |
- Sämfors, Sanna, 1987, et al.
(författare)
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Biofabrication of bacterial nanocellulose scaffolds with complex vascular structure
- 2019
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Ingår i: Biofabrication. - : IOP Publishing. - 1758-5082 .- 1758-5090. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial nanocellulose (BNC) has proven to be an effective hydrogel-like material for different tissue engineering applications due to its biocompatibility and good mechanical properties. However, as for all biomaterials, in vitro biosynthesis of large tissue constructs remains challenging due to insufficient oxygen and nutrient transport in engineered scaffold-cell matrices. In this study we designed, biofabricated and evaluated bacterial nanocellulose scaffolds with a complex vascular mimetic lumen structure. As a first step a method for creating straight channeled structures within a bacterial nanocellulose scaffold was developed and evaluated by culturing of Human Umbilical Vein Endothelial Cells (HUVECs). In a second step, more complex structures within the scaffolds were produced utilizing a 3D printer. A print mimicking a vascular tree acted as a sacrificial template to produce a network within the nanoporous bacterial nanocellulose scaffolds that could be lined with endothelial cells. In a last step, a method to produce large constructs with interconnected macro porosity and vascular like lumen structure was developed. In this process patient data from x-ray computed tomography scans was used to create a mold for casting a full-sized kidney construct. By showing that the 3D printing technology can be combined with BNC biosynthesis we hope to widen the opportunities of 3D printing, while also enabling the production of BNC scaffolds constructs with tailored vascular architectures and properties.
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