| 1. |
- Bannow, J., et al.
(författare)
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Solid nanofoams based on cellulose nanofibers and indomethacin—the effect of processing parameters and drug content on material structure
- 2017
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 526:1-2, s. 291-299
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Tidskriftsartikel (refereegranskat)abstract
- The unique colloidal properties of cellulose nanofibers (CNF), makes CNF a very interesting new excipient in pharmaceutical formulations, as CNF in combination with some poorly-soluble drugs can create nanofoams with closed cells. Previous nanofoams, created with the model drug indomethacin, demonstrated a prolonged release compared to films, owing to the tortuous diffusion path that the drug needs to take around the intact air-bubbles. However, the nanofoam was only obtained at a relatively low drug content of 21 wt% using fixed processing parameters. Herein, the effect of indomethacin content and processing parameters on the foaming properties was analysed. Results demonstrate that a certain amount of dissolved drug is needed to stabilize air-bubbles. At the same time, larger fractions of dissolved drug promote coarsening/collapse of the wet foam. The pendant drop/bubble profile tensiometry was used to verify the wet-foam stability at different pHs. The pH influenced the amount of solubilized drug and the processing-window was very narrow at high drug loadings. The results were compared to real foaming-experiments and solid state analysis of the final cellular solids. The parameters were assembled into a processing chart, highlighting the importance of the right combination of processing parameters (pH and time-point of pH adjustment) in order to successfully prepare cellular solid materials with up to 46 wt% drug loading.
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| 2. |
- Birdsong, Björn K., et al.
(författare)
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Flexible and fire-retardant silica/cellulose aerogel using bacterial cellulose nanofibrils as template material
- 2024
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Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 5:12, s. 5041-5051
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the possibility of using various silsesquioxane precursors such as (3-aminopropyl) triethoxysilane (APTES), methyltrimethoxysilane (MTMS), and tetraethyl orthosilicate (TEOS) to produce silsesquioxane-bacterial cellulose nanofibre (bCNF) aerogels. Each precursor allowed to customize the aerogel properties, leading to unique properties suitable for various applications requiring lightweight insulative materials. When utilizing APTES as the silsesquioxane precursor, an aerogel capable of over 90% recovery after compression was formed, making them suitable for flexible applications. When MTMS was used as the precursor, the aerogel retained some compression recovery (80%) but had the added property of superhydrophobicity with a contact angle over 160° due to the presence of CH3 functional groups, enabling water-repellence. Finally, TEOS allowed for excellent thermal insulative properties with a low Peak Heat Release Rate (PHRR), making it a promising candidate for fire-resistant applications. The customization of these aerogel materials was attributed to a combination of the chemical composition of the silsesquioxane precursors and the morphology of the coated bacterial cellulose nanofibres (bCNF), such as CH3 groups found in MTMS enabled for superhydrophobicity. Differences in morphology, such as uniform and smooth silsesquioxane coatings when using APTES or a “pearl-necklace” morphology using TEOS, enabled either compression recovery and flexibility or low thermal conduction. This investigation of silsesquioxane-bCNF provides a good understanding of the importance of the choice of precursor effect on insulating aerogel properties.
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| 3. |
- Svagan, Anna J., et al.
(författare)
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Cellulose Nanofiber/Nanocrystal Reinforced Capsules : A Fast and Facile Approach Toward Assembly of Liquid-Core Capsules with High Mechanical Stability
- 2014
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:5, s. 1852-1859
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Tidskriftsartikel (refereegranskat)abstract
- Liquid-core capsules of high mechanical stability open up for many solid state-like applications where functionality depending on liquid mobility is vital. Herein, a novel concept for fast and facile improvement of the mechanical properties of walls of liquid-core capsules is reported. By imitating nature's own way of enhancing the mechanical properties in liquid-core capsules, the parenchyma plant cells found in fruits and vegetables, a blend of short cellulose nanofibers (<1 mu m, NFC) and nanocrystals (CNC) was exploited in the creation of the capsule walls. The NFC/CNC blend was prepared from a new version of the classical wood pulp hydrolysis. The capsule shell consisted of a covalently (by aromatic diisocyanate) cross-linked NFC/CNC structure at the outer capsule wall and an inner layer dominated by aromatic polyurea. The mechanical properties revealed an effective capsule elastic modulus of 4.8 GPa at 17 wt % NFC/CNC loading, about six times higher compared to a neat aromatic polyurea capsule (0.79 GPa) and 3 orders of magnitude higher than previously reported capsules from regenerated cellulose (0.0074 GPa). The outstanding mechanical properties are ascribed to the dense nanofiber structure, present in the outer part of the capsule wall, that is formed by oriented NFC/CNC of high average aspect ratio (L/d similar to 70) and held together by both covalent (urethane bonds) and physical bonds (hydrogen bonds).
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| 4. |
- Cárdenas, Marité, et al.
(författare)
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Cellulose Nanofibers for Biomedical Applications
- 2016
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Ingår i: Biopolymers for Medical Applications. - Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 : CRC Press. - 9781498744966 ; , s. 213-232
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Bokkapitel (refereegranskat)abstract
- The creation of materials exploiting molecules from renewable resources and green processing routes in order to minimize contamination of the environment with toxic solvents and starting components, is an important step towards a sustainable society, and sustainable development is critical in all technological fields including biomedical engineering. In this context, the polysaccharides are an important family of molecules, as they can be derived from numerous natural sources including plants, bacteria, insects, animals, and also from by-products/waste-materials obtained from agricultural or fishery activities. Also, polysaccharides are biodegradable and can be broken down by common microorganisms found on land or in water. In nature, polysaccharides can be composed of one type of repeating unit (homopolysaccharides; starch and cellulose) or two or more types of repeating monomer (heteropolysaccharides; pectin, alginate). But despite using only a few basic building blocks, many unique and complex molecular structures with specific features and functions are assembled giving rise to a plethora of diverse carbohydrates. Some of the polysaccharides are classified as polyelectrolytes, and these are either negatively or positively charged. The intrinsic properties of such ionic polysaccharides are used in material science to produce stimuli-responsive materials where external stimuli (pH, ionic strength, and temperature) trigger, for example, a mechanical response in the material or a swelling mechanism that can be exploited in drug delivery. In addition to conventional polysaccharides, advanced genetic engineering also opens up the possibility for new, innovative, and structurally designed macromolecules with specific chemical and physical properties, allowing for better material structure-property control. Natural polysaccharides are typically biocompatible, possibly bioadhesive, and generally recognized as safe (GRAS) and, in conclusion, they are attractive materials to use in biomedical applications.
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| 5. |
- Lobmann, Korbinian, et al.
(författare)
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Cellulose nanofibers as excipient for the delivery of poorly soluble drugs
- 2017
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Ingår i: International Journal of Pharmaceutics. - : ELSEVIER SCIENCE BV. - 0378-5173 .- 1873-3476. ; 533:1, s. 285-297
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Tidskriftsartikel (refereegranskat)abstract
- Poor aqueous solubility of drugs is becoming an increasingly pronounced challenge in the formulation and development of drug delivery systems. To overcome the limitations associated with these problematic drugs, formulation scientists are required to use enabling strategies which often demands the use of new excipients. Cellulose nanofibers (CNFs) is such an excipient and it has only recently been described in the pharmaceutical field. In this review, the use of CNF in drug formulation with a focus on poorly soluble drugs is featured. In particular, the aim is to describe and discuss the many unique properties of CNFs, which make CNFs attractive as excipients in pharmaceutical sciences. Furthermore, the use of CNF as stabilizers for crystalline drug nanoparticles, as a matrix former to obtain a long-lasting sustained drug release over several weeks and as a film former with immediate release properties for poorly soluble drug are reported. Finally, the preparation of pharmaceutical CNF foams together with poorly soluble drugs is highlighted; foams, which offer a sustained drug delivery system with positive buoyancy.
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| 6. |
- Lombardo, S., et al.
(författare)
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Toward Improved Understanding of the Interactions between Poorly Soluble Drugs and Cellulose Nanofibers
- 2018
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 34:19, s. 5464-5473
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibers (CNFs) have interesting physicochemical and colloidal properties that have been recently exploited in novel drug-delivery systems for tailored release of poorly soluble drugs. The morphology and release kinetics of such drug-delivery systems heavily relied on the drug-CNF interactions; however, in-depth understanding of the interactions was lacking. Herein, the interactions between a poorly soluble model drug molecule, furosemide, and cationic cellulose nanofibers with two different degrees of substitution are studied by sorption experiments, Fourier transform infrared spectroscopy, and molecular dynamics (MD) simulation. Both MD simulations and experimental results confirmed the spontaneous sorption of drug onto CNF. Simulations further showed that adsorption occurred by the flat aryl ring of furosemide. The spontaneous sorption was commensurate with large entropy gains as a result of release of surface-bound water. Association between furosemide molecules furthermore enabled surface precipitation as indicated by both simulations and experiments. Finally, sorption was also found not to be driven by charge neutralization, between positive CNF surface charges and the furosemide negative charge, so that surface area is the single most important parameter determining the amount of sorbed drug. An optimized CNF-furosemide drug-delivery vehicle thus needs to have a maximized specific surface area irrespective of the surface charge with which it is achieved. The findings also provide important insights into the design principles of CNF-based filters suitable for removal of poorly soluble drugs from wastewater.
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| 7. |
- Löbmann, Korbinian, et al.
(författare)
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Cellulose Nanopaper and Nanofoam for Patient-Tailored Drug Delivery
- 2017
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Ingår i: Advanced Materials Interfaces. - : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 4:9
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Tidskriftsartikel (refereegranskat)abstract
- The development of drug delivery systems with tailored drug release can be very challenging especially in the case of problematic drugs. To address this problem, pharmaceutical scientists frequently use different formulation approaches and excipients, often involving a complex and multistep preparation. In this study, new cellulose nanofiber (CNF) based drug formulations are developed that allow controlled drug release in a facile and fast way, i.e., by simply casting drug/CNF dispersions. Altering the processing conditions and utilizing the unique inherent chemicophysical properties of cationic CNF at interfaces, it is possible to produce either drug-loaded CNF nanopapers (containing 21 or 51 wt% drug) or nanofoams (containing 21 wt% drug). The different formulations exhibit tailored release kinetics of the poorly watersoluble model drug indomethacin from immediate (nanopapers, 10-20 min) to slow release (nanofoams, approximate to 24 h). The fast release, from the nanopapers, is a result of the interplay of the molecular and supramolecular structure of indomethacin in addition to observed enhanced intrinsic dissolution of drug in the presence of CNF. The slower drug release is achieved by changing the hierarchical structure, i.e., creating a CNF based foam (porosity 99.2 wt%), and the prolonged release is mainly due to an extended drug diffusion path.
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| 8. |
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| 9. |
- Paulraj, Thomas, et al.
(författare)
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Bioinspired Layer-by-Layer Microcapsules Based on Cellulose Nanofibers with Switchable Permeability
- 2017
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 18:4, s. 1401-1410
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Tidskriftsartikel (refereegranskat)abstract
- Green, all-polysaccharide based microcapsules with mechanically robust capsule walls and fast, stimuli-triggered, and switchable permeability behavior show great promise in applications based on selective and timed permeability. Taking a cue from nature, the build-up and composition of plant primary cell walls inspired the capsule wall assembly, because the primary cell walls in plants exhibit high mechanical properties despite being in a highly hydrated state, primarily owing to cellulose microfibrils. The micro capsules (16 +/- 4 mu m in diameter) were fabricated using the layer-by-layer technique on sacrificial CaCO3 templates, using plant polysaccharides (pectin, cellulose nanofibers, and xyloglucan) only. In water, the capsule wall was permeable to labeled dextrans with a hydrodynamic diameter of similar to 6.6 nm. Upon exposure to NaC1, the porosity of the capsule wall quickly changed allowing larger molecules (similar to 12 nm) to permeate. However, the porosity could be restored to its original state by removal of NaCl, by which permeants became trapped inside the capsule's core. The high integrity of cell wall was due to the CNF and the ON/OFF alteration of the permeability properties, and subsequent loading/unloading of molecules, could be repeated several times with the same capsule demonstrating a robust microcontainer with controllable permeability properties.
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| 10. |
- Paulraj, Thomas, et al.
(författare)
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Porous Cellulose Nanofiber-Based Microcapsules for Biomolecular Sensing
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:48, s. 41146-41154
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibers (CNFs) have recently attracted a lot of attention in sensing because of their multifunctional character and properties such as renewability, nontoxicity, biodegradability, printability, and optical transparency in addition to unique physicochemical, barrier, and mechanical properties. However, the focus has exclusively been devoted toward developing two-dimensional sensing platforms in the form of nanopaper or nanocellulose-based hydrogels. To improve the flexibility and sensing performance in situ, for example, to detect biomarkers in vivo for early disease diagnostics, more advanced CNF-based structures are needed. Here, we developed porous and hollow, yet robust, CNF-based microcapsules using only the primary plant cell wall components, CNF, pectin, and xyloglucan, to assemble the capsule wall. The fluorescein isothiocyanate-labeled dextrans with M-w of 70 and 2000 kDa could enter the hollow capsules at a rate of 0.13 +/- 0.04 and 0.014 +/- 0.009 s(-1), respectively. This property is very attractive because it minimizes the influence of mass transport through the capsule wall on the response time. As a proof of concept, glucose oxidase (GOx) enzyme was loaded (and cross-linked) in the microcapsule interior with an encapsulation efficiency of 68 +/- 2%. The GOx-loaded microcapsules were immobilized on a variety of surfaces (here, inside a flow channel, on a carbon-coated sensor or a graphite rod) and glucose concentrations up to 10 mM could successfully be measured. The present concept offers new opportunities in the development of simple, more efficient, and disposable nanocellulose-based analytical devices for several sensing applications including environmental monitoring, healthcare, and diagnostics.
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