| 1. |
- Borde, Annika, 1979, et al.
(författare)
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Increased water transport in PDMS silicone films by addition of excipients
- 2012
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 8:2, s. 579-588
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Tidskriftsartikel (refereegranskat)abstract
- The development of new adhesive wound care products intended for an application over a prolonged time requires good water transporting properties of the adhesive for the maintenance of a suitable environment around the wound. The ability of polydimethylsiloxane (PDMS)-based silicone films to transport water has led to its use in skin pressure-sensitive adhesives and it would be advantageous to find ways for controlling or increasing water transport across PDMS films in order to be able to develop improved skin adhesives. In this study we present a way to increase water transport in such films by the addition of hydrophilic excipients. Three hydrophilic additives, highly water-soluble sucrose and the two superabsorbent polymers (SAP) Carbopol® and Pemulen™, were investigated. The effect of the excipients was characterized by water transport studies, swelling tests, scanning electron microscopy imaging and confocal microscopy. The cross-linked polymers, primarily Pemulen™, were efficient water transport enhancers, whereas sucrose did not show any effect. The effect of the additives seemed to correlate with their water binding capacity. For SAPs the formation of a percolating structure by swollen polymer was also suggested, which enhances water penetration by the higher volume fraction of areas with a higher diffusion constant (swollen SAP), leading to a faster transport through the entire film. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 2. |
- Gårdebjer, Sofie, 1985, et al.
(författare)
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An overview of the transport of liquid molecules through structured polymer films, barriers and composites - Experiments correlated to structure-based simulations
- 2018
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686. ; 256, s. 48-64
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Tidskriftsartikel (refereegranskat)abstract
- Films engineered to control the transport of liquids are widely used through society. Examples include barriers in packaging, wound care products, and controlled release coatings in pharmaceutics. When observed at the macroscopic scale such films commonly appear homogeneous, however, a closer look reveals a complex nano and microstructure that together with the chemical properties of the different domains control the transport properties. In this review we compare and discuss macroscopic transport properties, measured using the straightforward, yet highly powerful technique "modified Ussing chambers", also denoted side-by-side diffusion cells, for a wide range of structured polymer films and composites. We also discuss and compare the macroscopic observations and conclusions on materials properties with that of lattice Boltzmann simulations of transport properties based on underlying material structure and chemistry. The survey of the field: (i) highlights the use and power of modified Ussing Chambers for determining liquid transport properties of polymer films, (ii) demonstrates the predictability in both directions between macroscopic observations of transport using modified Ussing chambers and structure-based simulations, and (iii) provides experimental and theoretical insights regarding the transport-determining properties of structured polymer films and composites. (C) 2018 Elsevier B.V. All rights reserved.
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| 3. |
- Hsiao, Meng-Hsuan, et al.
(författare)
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Design and characterization of a novel amphiphilic chitosan nanocapsule-based thermo-gelling biogel with sustained in vivo release of the hydrophilic anti-epilepsy drug ethosuximide
- 2012
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 161:3, s. 942-948
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Tidskriftsartikel (refereegranskat)abstract
- Thermo-gelling injectable nanogels, with no burst release of loaded drug, were prepared by a simple route by combining self assembled nanocapsules of amphiphilically modified chitosan with glycerophosphate di-sodium salt and glycerol. The potential as a depot drug delivery system was demonstrated in vivo through the therapeutic effect of ethosuximide (ESM) loaded nanogels, suppressing spike wave discharges (SWDs) in Long Evan rat model. Simultaneously clearance of gels from the site of administration was monitored non-invasively using MRI. The gel structure was characterized using TEM and SEM, confirming the gels to be an assembly of nanocapsules and using two-photon microscopy to visualize the network structure. In vitro drug release studies using ESM revealed that the nanogels exhibited extended, mostly Fickian release. Finally, all investigated formulations displayed excellent cytotoxicity data determined by MTT assay using human retinal pigmented epithelium cells. All presented properties are highly desirable for injectable depot gels for drug delivery.
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| 4. |
- Larsson, Mikael, 1982, et al.
(författare)
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Determination of the glass transition of powder samples using Dynamic Mechanic Analysis on compacts
- 2010
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Ingår i: Annual Transactions - The Nordic Rheology Society. - 1601-4057. ; 18, s. 59-64
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic Mechanic Analysis, DMA, is asensitive method to determine the glasstransition temperature (Tg) of materials.Several different sample geometries such asthree point bending, stretched films orcompressed cylinders, are commonly used.The Tg of a powder is related to its “stickypoint”, i.e. the temperature when the powderparticles interact instead of flowing freely.The determination of powder Tg is notstraightforward using DMA due to thelimiting geometry. Here it is demonstratedthat the Tg of powder samples canbe effectively and correctly determinedby DMA on compacts in compression mode,using a standard wedge shaped probe usuallyutilized in three point bend analysis. Theanalysis of compacts holds the benefits ofanalysing powder samples as received frommanufacturers, being relatively robust withregard to deformation as the materialbecomes rubbery, and enabling easy samplepreparation and handling.
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| 5. |
- Larsson, Mikael, 1982, et al.
(författare)
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Different types of microfibrillated cellulose as filler materials in polysodium acrylate superabsorbents
- 2011
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Ingår i: Chinese Journal of Polymer Science (English Edition). - : Springer Science and Business Media LLC. - 1439-6203 .- 0256-7679. ; 29:4, s. 407-413
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Tidskriftsartikel (refereegranskat)abstract
- Three types of microfibrillated cellulose (MFC) with differences in structure and surface charge were used at low concentration as filler materials in polysodium acrylate superabsorbents (SAPs). The swelling of the composite hydrogels was determined in 0.9% NaCl solution as well as in deionized water. The shear modulus of the samples was determined through uniaxial compression analysis after synthesis and after swelling in 0.9% NaCl solution. Furthermore, the ability to retain filler effects after washing was investigated. The results showed that all of the investigated MFCs had a strong reinforcing effect on the shear modulus after synthesis. The filler effect on swelling and on the associated shear modulus of swollen samples showed a more complicated dependence on structure and surface charge. Finally, it was found that the filler effects were reasonably retained after washing and subsequent drying. The results confirm that MFC holds great potential as a filler material in superabsorbent applications. Furthermore, the results provide some insight on how the structural properties and surface charge of MFC will affect gel properties depending on swelling conditions. This information should be useful in evaluating the use of different types of MFC in future applications.
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| 6. |
- Larsson, Mikael, 1982, et al.
(författare)
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Effect of calcium neutralization on elastic and swelling properties of crosslinked poly(acrylic acid) - correlation to inhomogeneities and phase behaviour
- 2009
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Ingår i: E-Polymers. - 1618-7229. ; :141, s. 1683-1696
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Tidskriftsartikel (refereegranskat)abstract
- Crosslinked hydrogels of poly(acrylic acid) neutralized with calcium hydroxide were synthesized using free radical co-polymerization. The effects of the amount added calcium on the elastic modulus and swelling properties of the gels and the correlation to phase behaviour and structural changes within the gels were studied using texture analysis, gravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and atomic force microscopy (AFM). It was found that the elastic modulus decreased nonlinearly with increasing amount of added calcium and that the swelling's dependence on the amount of added calcium was complicated. The maximum swelling increased with increasing amount of added calcium until a critical calcium content was reached, upon which the gels phase separated, with a strong decrease in swelling as a result. The changes in properties are explained by the fact that calcium affects the structure of the polymer network during synthesis and by the phase behaviour of the gels. Changes in the gel structure with the addition of calcium were detected with AFM. Furthermore, AFM revealed different phases on the nanometre scale for the sample with a calcium content around which phase separation is macroscopically observed. Finally, it was shown that the sulphur from the initiator potassium persulfate formed crystal like regions with high sulphur and calcium content upon drying of the hydrogels.
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| 7. |
- Larsson, Mikael, 1982, et al.
(författare)
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Effect of ethanol on the water permeability of controlled release films composed of ethyl cellulose and hydroxypropyl cellulose
- 2010
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Ingår i: European Journal of Pharmaceutics and Biopharmaceutics. - : Elsevier BV. - 1873-3441 .- 0939-6411. ; 76:3, s. 428-432
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Tidskriftsartikel (refereegranskat)abstract
- The robustness of controlled release formulations when co-ingested with alcohol is a current concern expressed by regulatory authorities, especially with regard to dose dumping. One such controlled release formulation commonly used is film coating composed of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC). The aim of this study was to investigate how the presence of ethanol in the dissolution medium affects the water permeability of such films. Film samples were prepared in various EC–HPC compositions, and the effect of different ethanol concentrations in the dissolution medium on the permeability was studied using a modified Ussing chamber and tritiated water. It was found that the effect of ethanol on the film permeability varied depending on the composition of the films. The results were interpreted in terms of swelling of the EC in the films, where the swelling increased with increasing ethanol concentration. Thus, for films with low HPC content (non-interconnected pores), the water permeability of the films increased with increasing ethanol concentration as the diffusion through the ethyl cellulose increased due to swelling. However, for films with higher HPC content (having interconnected pores through the films), the permeability decreased, likely due to the swelling of the ethyl cellulose blocking the pores. The interpretation of the results was supported by dynamic mechanic analysis and SEM analysis.
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| 8. |
- Larsson, Mikael, 1982, et al.
(författare)
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Evaluation of Carboxymethyl-Hexanoyl Chitosan as a Protein Nanocarrier
- 2013
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Ingår i: Nanomaterials and Nanotechnology. - : SAGE Publications. - 1847-9804. ; 3:1, s. Art. no. 7-
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Tidskriftsartikel (refereegranskat)abstract
- Carboxymethyl‐hexanoyl chitosan (CHC) has the ability to self‐assemble into nanocapsules in anaqueous solution and it has recently shown potentialin numerous biomedical applications. Here weinvestigate the protein loading efficiency and release,as well as the structural properties of CHC proteinnanocarriers. Bovine serum albumin (BSA) or itschromophore labelled version, fluorescein‐BSA, wasused as a model protein and the loading wasperformed with a simple mixing of pre‐formednanocapsules and protein. Dynamic light scatteringand zeta potential analysis revealed that proteinloaded nanocarriers with high positive zeta potentialwere formed. The protein loaded nanocarriersdisplayed a loading efficiency of 75% and a very slowprotein release. In summary, our results highlight thepotential of CHC as a protein nanocarrier, but alsoindicate that protein‐CHC interactions need to beconsidered in protein containing CHC formulationswhere protein release is not the main function.
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| 9. |
- Larsson, Mikael, 1982, et al.
(författare)
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High Performance Polysodium Acrylate Superabsorbents Utilizing Microfibrillated Cellulose to Augment Gel Properties
- 2010
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Ingår i: Soft Materials. - 1539-445X .- 1539-4468. ; 8:3, s. 207-225
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Tidskriftsartikel (refereegranskat)abstract
- Microfibrillated cellulose was utilized at low concentrations as a filler material, added prior to free radical polymerization, in cross-linked superabsorbent polysodium acrylate hydrogels. The effect of microfibrillated cellulose concentration on equilibrium swelling, shear modulus after synthesis, and shear modulus at equilibrium swelling was studied at different degree of cross-linking. For the characterization of the microfibrillated cellulose optical microscopy, atomic force microscopy, and transmittance analysis were used. The shear modulus of the samples was determined using uniaxial compression analysis. The swelling of the gels was determined using classical gravimetrical measurements. It was found that microfibrillated cellulose was highly efficient in increasing the shear modulus of the gels. Furthermore, the microfibrillated cellulose was found to have the same effect on the swelling and shear modulus at equilibrium swelling as the same mass of the conventional covalent cross-linker N,N'-methylenebisacrylamide (MBA), while in fact improving the fracture resistance of the gels. In conclusion, microfibrillated cellulose shows great potential as an additive to enhance the performance of soft materials.
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| 10. |
- Larsson, Mikael, 1982, et al.
(författare)
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Nanocomposites of polyacrylic acid nanogels and biodegradable polyhydroxybutyrate for bone regeneration and drug delivery
- 2014
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Ingår i: Journal of Nanomaterials. - : Hindawi Limited. - 1687-4129 .- 1687-4110. ; 2014, s. Art. no. 371307-
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable cell scaffolds and local drug delivery to stimulate cell response are currently receiving much scientific attention. Here we present a nanocomposite that combines biodegradation with controlled release of lithium, which is known to enhance bone growth. Nanogels of lithium neutralized polyacrylic acid were synthesized by microemulsion-templated polymerization and were incorporated into a biodegradable polyhydroxybutyrate (PHB) matrix. Nanogel size was characterized using dynamic light scattering, and the nanocomposites were characterized with regard to structure using scanning electron microscopy, mechanical properties using tensile testing, permeability using tritiated water, and lithium release in PBS using a lithium specific electrode. The nanogels were well dispersed in the composites and the mechanical properties were good, with a decrease in elastic modulus being compensated by increased tolerance to strain in the wet state. Approximately half of the lithium was released over about three hours, with the remaining fraction being trapped in the PHB for subsequent slow release during biodegradation. The prepared nanocomposites seem promising for use as dual functional scaffolds for bone regeneration. Here lithium ions were chosen as model drug, but the nanogels could potentially act as carriers for larger and more complex drugs, possibly while still carrying lithium.
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