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| 2. |
- Kaldéus, Tahani, et al.
(författare)
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Molecular Engineering of the Cellulose-Poly(Caprolactone) Bio-Nanocomposite Interface by Reactive Amphiphilic Copolymer Nanoparticles
- 2019
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 13:6, s. 6409-6420
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Tidskriftsartikel (refereegranskat)abstract
- A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.
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| 3. |
- Matthiesen, Isabelle, et al.
(författare)
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Astrocyte 3D culture and bioprinting using peptide functionalized hyaluronan hydrogels
- 2023
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Ingår i: Science and Technology of Advanced Materials. - : Informa UK Limited. - 1468-6996 .- 1878-5514. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- Astrocytes play an important role in the central nervous system, contributing to the development of and maintenance of synapses, recycling of neurotransmitters, and the integrity and function of the blood-brain barrier. Astrocytes are also linked to the pathophysiology of various neurodegenerative diseases. Astrocyte function and organization are tightly regulated by interactions mediated by the extracellular matrix (ECM). Engineered hydrogels can mimic key aspects of the ECM and can allow for systematic studies of ECM-related factors that govern astrocyte behaviour. In this study, we explore the interactions between neuroblastoma (SH-SY5Y) and glioblastoma (U87) cell lines and human fetal primary astrocytes (FPA) with a modular hyaluronan-based hydrogel system. Morphological analysis reveals that FPA have a higher degree of interactions with the hyaluronan-based gels compared to the cell lines. This interaction is enhanced by conjugation of cell-adhesion peptides (cRGD and IKVAV) to the hyaluronan backbone. These effects are retained and pronounced in 3D bioprinted structures. Bioprinted FPA using cRGD functionalized hyaluronan show extensive and defined protrusions and multiple connections between neighboring cells. Possibilities to tailor and optimize astrocyte-compatible ECM-mimicking hydrogels that can be processed by means of additive biofabrication can facilitate the development of advanced tissue and disease models of the central nervous system.
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| 4. |
- Pendergraph, Sam, et al.
(författare)
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Macroscopic cellulose probes for contact adhesion
- 2015
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Ingår i: Abstracts of Papers of the American Chemical Society. - : AMER CHEMICAL SOC. - 0065-7727. ; 249
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Reid, Michael S., et al.
(författare)
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Tunable Adhesion and Interfacial Structure of Layer-by-Layer Assembled Block co-polymer Micelle and Polyelectrolyte Coatings
- 2022
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 9:17, s. 2200065-
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and tuning nanoscale structure is critical in developing new coatings and adhesives. In this work layer-by-layer assembly of block co-polymer (BCP) micelles and oppositely charged polyelectrolytes produces structurally unique coatings with wet adhesion comparable to that of mussel adhesive proteins. Cationic (CAT) and anionic (ANI) BCPs, synthesized by atom transfer radical polymerization (ATRP), are used to create colloidally stable, self-assembled, spherical BCP micelles. The assembly of BCP micelle and polyelectrolyte multilayers is monitored in situ where CAT- and ANI-BCP micelles exhibit linear and super-linear growth, respectively. Imaging of the surfaces reveals that CAT-BCP micelles yield flat, uniform layers whereas ANI-BCP micelle assemblies form islands that increase in surface area with each additional layer. The adhesion of these layers, measured by colloidal probe atomic force microscopy (CP-AFM), shows that the distinct layers of CAT-BCP micelle assemblies produce alternating high and low adhesion surfaces whereas ANI-BCP micelle assemblies continually increase in adhesion with each additional bilayer. The unique behavior of each assembly demonstrates that both composition and structure play important roles in wet adhesion of submicron layers and that each can be tuned to target performance for different applications.
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| 6. |
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| 7. |
- Träger, Andrea, et al.
(författare)
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Interpenetrated Networks of Nanocellulose and Polyacrylamide with Excellent Mechanical and Absorptive Properties
- 2018
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Ingår i: Macromolecular materials and engineering. - : Wiley. - 1438-7492 .- 1439-2054. ; 303:5
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Tidskriftsartikel (refereegranskat)abstract
- Composites based on interpenetrating networks (IPNs) of cellulose nanofibril (CNF) aerogels and polyacrylamide are prepared and exhibit robust mechanical, water retaining, and re-swelling capacities. Furthermore, their swelling behavior is not affected by an increased ionic strength of the aqueous phase. These unprecedented IPNs combine the water retaining capacity of the polyacrylamide with the mechanical strength provided by the CNF aerogel template. The CNF aerogel/polyacrylamide composites exhibit a compressive stress at break greater than 250% compared with a neat polyacrylamide hydrogel. Furthermore, the composites retain their wet compression properties after drying and re-swelling, whereas the neat polyacrylamide hydrogels fail at a significantly lower stress and strain after drying and re-swelling. These composite materials highlight the potential of CNF aerogels to strengthen the mechanical properties and reduce the number of fracture defects during the drying and re-swelling of a hydrogel. These composites show the potential of being optimized for a plethora of applications, especially in the hygiene field and for biomedical devices.
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| 8. |
- Träger, Andrea, et al.
(författare)
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Macroscopic cellulose probes for the measurement of polymer grafted surfaces
- 2019
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 26:3, s. 1467-1477
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: A synthesis protocol was identified to produce covalent grafting of poly(dimethyl siloxane) from cellulose, based on prior studies of analogous ring opening polymerizations. Following this polymer modification of cellulose, the contact adhesion was anticipated to be modified and varied as a function of the polymer molecular mass. The synthetic details were optimized for a filter paper surface before grafting the polymer from bulk cellulose spheres. The adhesion of the unmodified and grafted, bulk cellulose spheres were evaluated using the Johnson–Kendall–Roberts (JKR) theory with a custom build contact adhesion testing setup. We report the first example of grafting poly(dimethyl siloxane) directly from bulk cellulose using ring opening polymerization. For short grafting lengths, both the JKR work of adhesion and the adhesion energy at the critical energy release rate (Gc) were comparable to unmodified cellulose beads. When polymer grafting lengths were extended sufficiently where chain entanglements occur, both the JKR work of adhesion and Gc were increased by as much as 190%. Given the multitude of options available to graft polymers from cellulose, this study shows the potential to use this type of cellulose spheres to study the interaction between different polymer surfaces in a controlled manner. Graphical abstract: [Figure not available: see fulltext.].
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| 9. |
- Träger, Andrea, et al.
(författare)
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Nanocellulose Reinforced Hyaluronan-Based Bioinks
- 2023
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Ingår i: Biomacromolecules. - : AMER CHEMICAL SOC. - 1525-7797 .- 1526-4602. ; 24:7, s. 3086-3093
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Tidskriftsartikel (refereegranskat)abstract
- Bioprinting of hydrogel-based bioinks can allow for thefabricationof elaborate, cell-laden 3D structures. In addition to providing anadequate extracellular matrix mimetic environment and high cell viability,the hydrogels must offer facile extrusion through the printing nozzleand retain the shape of the printed structure. We demonstrate a strategyto incorporate cellulose oxalate nanofibrils in hyaluronan-based hydrogelsto generate shear thinning bioinks that allowed for printing of free-standingmultilayer structures, covalently cross-linked after bioprinting,yielding long-term stability. The storage modulus of the hydrogelswas tunable between 0.5 and 1.5 kPa. The nanocellulose containinghydrogels showed good biocompatibility, with viability of primaryhuman dermal fibroblasts above 80% at day 7 after seeding. The cellswere also shown to tolerate the printing process well, with viabilityabove 80% 24 h after printing. We anticipate that this hydrogel systemcan find broad use as a bioink to produce complex geometries thatcan support cell growth.
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| 10. |
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| 11. |
- Träger, Andrea
(författare)
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Strategies for Molecular Engineering of Macroscopic Adhesion and Integrity Focusing on Cellulose Based Materials
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many aspects of modern human life pose a strain on the delicate ecosystems around us. One example is marine litter – mainly various plastic items – which accumulate in the marine environment, where they cause problems for the fauna, such as ingestion and entanglement.The widely used plastics offer many advantages for packaging, such as low cost and easy processing into many shapes. However, in addition to their low biodegradability leading to their persistence and accumulation in nature, they are largely manufactured from petroleum,a non‐renewable resource. Clearly, it would be highly desirable to exchange the petroleum‐based materials for biodegradable ones from renewable resources. Cellulose, as the most abundant biopolymer, is one choice. There are however challenges in terms of replacing currently used plastics with cellulosic materials. One is the low ductility and formability of cellulose. Various efforts are undertaken to increase the formability of cellulose. One approach to increase the renewable fraction within a material is to utilise the intrinsic stiffness and strength of cellulose to increase the structural integrity of a composite. To fully optimise these types of materials, a fundamental understanding of the interaction across interfaces within the material is essential. The main objective in this thesis was to elucidate strategies to measure, to tune and to control the interaction across interfaces. Specific polymers were designed and synthesised which could be used to modify surfaces to achieve a wet adhesion as high as that of mussel foot protein. Many properties of the joint were tuneable by varying length and structure of the polymer and amount of polymer deposited on the surfaces. A method to accurately evaluate interfacial adhesion between a chemically modified cellulose material and another surface was successfully developed, using nanometre smooth cellulose probes exhibiting bulk material properties. Two composite materials containing cellulose as reinforcing element were successfully prepared,utilising different strategies to control and enhance the interaction between the composite constituents. Together, these findings contribute to the knowledge of how to evaluate and control the interaction across an interface.
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| 12. |
- Träger, Andrea, et al.
(författare)
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Strong and tuneable wet adhesion with rationally designed layer-by-layer assembled triblock copolymer films
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 8:42, s. 18204-18211
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Tidskriftsartikel (refereegranskat)abstract
- this study the wet adhesion between Layer-by-Layer (LbL) assembled films of triblock copolymer micelles was investigated. Through the LbL assembly of triblock copolymer micelles with hydrophobic, low glass transition temperature (T-g) middle blocks and ionic outer blocks, a network of energy dissipating polymer chains with electrostatic interactions serving as crosslinks can be built. Four triblock copolymers were synthesized through Atom Transfer Radical Polymerisation (ATRP). One pair had a poly(2-ethyl-hexyl methacrylate) middle block with cationic or anionic outer blocks. The other pair contained the same ionic outer blocks but poly(n-butyl methacrylate) as the middle block. The wet adhesion was evaluated with colloidal probe AFM. To our knowledge, wet adhesion of the magnitude measured in this study has not previously been measured on any polymer system with this technique. We are convinced that this type of block copolymer system grants the ability to control the geometry and adhesive strength in a number of nano-and macroscale applications.
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