| 1. |
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| 2. |
- Carmona, Pierre, 1995, et al.
(författare)
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Controlling the structure of spin-coated multilayer ethylcellulose/ hydroxypropylcellulose films for drug release
- 2023
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 644
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Tidskriftsartikel (refereegranskat)abstract
- Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. Water-soluble HPC leaches out and forms a porous structure that controls the drug transport. Industrially, the pellets are coated using a fluidized bed spraying device, and a layered film exhibiting varying porosity and structure after leaching is obtained. A detailed understanding of the formation of the multilayered, phase-separated structure during production is lacking. Here, we have investigated multilayered EC/HPC films produced by sequential spin-coating, which was used to mimic the industrial process. The effects of EC/HPC ratio and spin speed on the multilayer film formation and structure were investigated using advanced microscopy techniques and image analysis. Cahn-Hilliard simulations were performed to analyze the mixing behavior. A gradient with larger structures close to the substrate surface and smaller structures close to the air surface was formed due to coarsening of the layers already coated during successive deposition cycles. The porosity of the multilayer film was found to vary with both EC/HPC ratio and spin speed. Simulation of the mixing behavior and in situ characterization of the structure evolution showed that the origin of the discontinuities and multilayer structure can be explained by the non-mixing of the layers.
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| 3. |
- Carmona, Pierre, 1995, et al.
(författare)
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Cross-sectional structure evolution of phase-separated spin-coated ethylcellulose/hydroxypropylcellulose films during solvent quenching
- 2022
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 12:40, s. 26078-26089
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Tidskriftsartikel (refereegranskat)abstract
- Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. The films are applied on the pellets using fluidized bed spraying. The drug transport rate is determined by the structure of the porous films that are formed as the water-soluble HPC leaches out. However, a detailed understanding of the evolution of the phase-separated structure during production is lacking. Here, we have investigated EC/HPC films produced by spin-coating, which mimics the industrial manufacturing process. This work aimed to understand the structure formation and film shrinkage during solvent evaporation. The cross-sectional structure evolution was characterized using confocal laser scanning microscopy (CLSM), profilometry and image analysis. The effect of the EC/HPC ratio on the cross-sectional structure evolution was investigated. During shrinkage of the film, the phase-separated structure undergoes a transition from 3D to nearly 2D structure evolution along the surface. This transition appears when the typical length scale of the phase-separated structure is on the order of the thickness of the film. This was particularly pronounced for the bicontinuous systems. The shrinkage rate was found to be independent of the EC/HPC ratio, while the initial and final film thickness increased with increasing HPC fraction. A new method to estimate part of the binodal curve in the ternary phase diagram for EC/HPC in ethanol has been developed. The findings of this work provide a good understanding of the mechanisms responsible for the morphology development and allow tailoring of thin EC/HPC films structure for controlled drug release.
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| 4. |
- Carmona, Pierre, 1995, et al.
(författare)
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Structure evolution during phase separation in spin-coated ethylcellulose/hydroxypropylcellulose films
- 2021
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Ingår i: Soft Matter. - : Royal Society of Chemistry. - 1744-683X .- 1744-6848. ; 17:14, s. 3913-3922
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Tidskriftsartikel (refereegranskat)abstract
- Porous phase-separated films made of ethylcellulose (EC) and hydroxypropylcellulose (HPC) are commonly used for controlled drug release. The structure of these thin films is controlling the drug transport from the core to the surrounding liquids in the stomach or intestine. However, detailed understanding of the time evolution of these porous structures as they are formed remains elusive. In this work, spin-coating, a widely applied technique for making thin uniform polymer films, was used to mimic the industrial manufacturing process. The focus of this work was on understanding the structure evolution of phase-separated spin-coated EC/HPC films. The structure evolution was determined using confocal laser scanning microscopy (CLSM) and image analysis. In particular, we determined the influence of spin-coating parameters and EC : HPC ratio on the final phase-separated structure and the film thickness. The film thickness was determined by profilometry and it influences the ethanol solvent evaporation rate and thereby the phase separation kinetics. The spin speed was varied between 1000 and 10 000 rpm and the ratio of EC : HPC in the polymer blend was varied between 78 : 22 wt% and 40 : 60 wt%. The obtained CLSM micrographs showed phase separated structures, typical for the spinodal decomposition phase separation mechanism. By using confocal laser scanning microscopy combined with Fourier image analysis, we could extract the characteristic length scale of the phase-separated final structure. Varying spin speed and EC : HPC ratio gave us precise control over the characteristic length scale and the thickness of the film. The results showed that the characteristic length scale increases with decreasing spin speed and with increasing HPC ratio. The thickness of the spin-coated film decreases with increasing spin speed. It was found that the relation between film thickness and spin speed followed the Meyerhofer equation with an exponent close to 0.5. Furthermore, good correlations between thickness and spin speed were found for the compositions 22 wt% HPC, 30 wt% HPC and 45 wt% HPC. These findings give a good basis for understanding the mechanisms responsible for the morphology development and increase the possibilities to tailor thin EC/HPC film structures.
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| 5. |
- Carmona, Pierre, 1995, et al.
(författare)
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Structure formation and coarsening kinetics of phase-separated spin-coated ethylcellulose/hydroxypropylcellulose films
- 2022
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Ingår i: Soft Matter. - : Royal Society of Chemistry. - 1744-683X .- 1744-6848. ; 18:16, s. 3206-3217
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Tidskriftsartikel (refereegranskat)abstract
- Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport from pharmaceutical pellets. The drug transport rate is determined by the structure of the porous films that are formed as water-soluble HPC leaches out. However, a detailed understanding of the evolution of the phase-separated structure in the films is lacking. In this work, we have investigated EC/HPC films produced by spin-coating, mimicking the industrial fluidized bed spraying. The aim was to investigate film structure evolution and coarsening kinetics during solvent evaporation. The structure evolution was characterized using confocal laser scanning microscopy and image analysis. The effect of the EC:HPC ratio (15 to 85 wt% HPC) on the structure evolution was determined. Bicontinuous structures were found for 30 to 40 wt% HPC. The growth of the characteristic length scale followed a power law, L(t) ∼ t(n), with n ∼ 1 for bicontinuous structures, and n ∼ 0.45-0.75 for discontinuous structures. The characteristic length scale after kinetic trapping ranged between 3.0 and 6.0 μm for bicontinuous and between 0.6 and 1.6 μm for discontinuous structures. Two main coarsening mechanisms could be identified: interfacial tension-driven hydrodynamic growth for bicontinuous structures and diffusion-driven coalescence for discontinuous structures. The 2D in-plane interface curvature analysis showed that the mean curvature decreased as a function of time for bicontinuous structures, confirming that interfacial tension is driving the growth. The findings of this work provide a good understanding of the mechanisms responsible for morphology development and open for further tailoring of thin EC/HPC film structures for controlled drug release. © 2022 The Royal Society of Chemistry
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| 6. |
- De Kort, Daan W., et al.
(författare)
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Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry
- 2018
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 34:37, s. 11110-11120
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Tidskriftsartikel (refereegranskat)abstract
- A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8-11 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H pulsed-field gradient NMR, fluorescence recovery after photobleaching, and raster image correlation spectroscopy revealed a fast and a slow component, pointing toward microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modeled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser dynamic nuclear polarization-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-labeled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modeling of transport through and release of solutes from heterogeneous biopolymer gels.
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| 7. |
- Deschout, Hendrik, et al.
(författare)
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Straightforward FRAP for quantitative diffusion measurements with a laser scanning microscope
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:22, s. 22886-22905
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Tidskriftsartikel (refereegranskat)abstract
- Confocal or multi-photon laser scanning microscopes are convenient tools to perform FRAP diffusion measurements. Despite its popularity, accurate FRAP remains often challenging since current methods are either limited to relatively large bleach regions or can be complicated for non-specialists. In order to bring reliable quantitative FRAP measurements to the broad community of laser scanning microscopy users, here we have revised FRAP theory and present a new pixel based FRAP method relying on the photo bleaching of rectangular regions of any size and aspect ratio. The method allows for fast and straightforward quantitative diffusion measurements due to a closed–form expression for the recovery process utilizing all available spatial and temporal data. After a detailed validation, its versatility is demonstrated by diffusion studies in heterogeneous biopolymer mixtures.
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| 8. |
- Eriksson Barman, Sandra, 1985, et al.
(författare)
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New characterization measures of pore shape and connectivity applied to coatings used for controlled drug release
- 2021
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 1520-6017 .- 0022-3549. ; 110:7, s. 2753-2764
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Tidskriftsartikel (refereegranskat)abstract
- Pore geometry characterization-methods are important tools for understanding how pore structure influences properties such as transport through a porous material. Bottlenecks can have a large influence on transport and related properties. However, existing methods only catch certain types of bottleneck effects caused by variations in pore size. We here introduce a new measure, geodesic channel strength, which captures a different type of bottleneck effect caused by many paths coinciding in the same pore. We further develop new variants of pore size measures and propose a new way of visualizing 3-D characterization results using layered images. The new measures together with existing measures were used to characterize and visualize properties of 3-D FIB-SEM images of three leached ethyl-cellulose/hydroxypropyl-cellulose films. All films were shown to be anisotropic, and the strongest anisotropy was found in the film with lowest porosity. This film had very tortuous paths and strong geodesic channel-bottlenecks, while the paths through the other two films were relatively straight with well-connected pore networks. The geodesic channel strength was shown to give important new visual and quantitative insights about connectivity, and the new pore size measures provided useful information about anisotropies and inhomogeneities in the pore structures. The methods have been implemented in the freely available software MIST.
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| 9. |
- Fager, Cecilia, 1990, et al.
(författare)
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3D high spatial resolution visualisation and quantification of interconnectivity in polymer films
- 2020
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Ingår i: International Journal of Pharmaceutics. - : Elsevier B.V.. - 0378-5173 .- 1873-3476. ; 587
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Tidskriftsartikel (refereegranskat)abstract
- A porous network acts as transport paths for drugs through films for controlled drug release. The interconnectivity of the network strongly influences the transport properties. It is therefore important to quantify the interconnectivity and correlate it to transport properties for control and design of new films. This work presents a novel method for 3D visualisation and analysis of interconnectivity. High spatial resolution 3D data on porous polymer films for controlled drug release has been acquired using a focused ion beam (FIB) combined with a scanning electron microscope (SEM). The data analysis method enables visualisation of pore paths starting at a chosen inlet pore, dividing them into groups by length, enabling a more detailed quantification and visualisation. The method also enables identification of central features of the porous network by quantification of channels where pore paths coincide. The method was applied to FIB-SEM data of three leached ethyl cellulose (EC)/hydroxypropyl cellulose (HPC) films with different weight percentages. The results from the analysis were consistent with the experimentally measured release properties of the films. The interconnectivity and porosity increase with increasing amount of HPC. The bottleneck effect was strong in the leached film with lowest porosity.
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| 10. |
- Fager, Cecilia, 1990, et al.
(författare)
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Correlating 3D porous structure in polymer films with mass transport properties using FIB-SEM tomography
- 2021
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Ingår i: Chemical Engineering Science: X. - : Elsevier BV. - 2590-1400. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Porous polymer coatings are used to control drug release from pharmaceutical products. The coating covers a drug core and depending on the porous structure, different drug release rates are obtained. This work presents mass transport simulations performed on porous ethyl cellulose films with different porosities. The simulations were performed on high spatial resolution 3D data obtained using a focused ion beam scanning electron microscope. The effective diffusion coefficient of water was determined using a diffusion chamber. Lattice Boltzmann simulations were used to simulate water diffusion in the 3D data. The simulated coefficient was in good agreement with the measured coefficient. From the results it was concluded that the tortuosity and constrictivity of the porous network increase with decreasing amount of added hydroxypropyl cellulose, resulting in a sharp decrease in effective diffusion. This work shows that high spatial resolution 3D data is necessary, and that 2D data is insufficient, in order to predict diffusion through the porous structure with high accuracy.
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| 11. |
- Fager, Cecilia, 1990, et al.
(författare)
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Optimization of FIB-SEM Tomography and Reconstruction for Soft, Porous, and Poorly Conducting Materials
- 2020
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Ingår i: Microscopy and Microanalysis. - 1431-9276 .- 1435-8115. ; 26:4, s. 837-845
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Tidskriftsartikel (refereegranskat)abstract
- Tomography using a focused ion beam (FIB) combined with a scanning electron microscope (SEM) is well-established for a wide range of conducting materials. However, performing FIB-SEM tomography on ion- and electron-beam-sensitive materials as well as poorly conducting soft materials remains challenging. Some common challenges include cross-sectioning artifacts, shadowing effects, and charging. Fully dense materials provide a planar cross section, whereas pores also expose subsurface areas of the planar cross-section surface. The image intensity of the subsurface areas gives rise to overlap between the grayscale intensity levels of the solid and pore areas, which complicates image processing and segmentation for three-dimensional (3D) reconstruction. To avoid the introduction of artifacts, the goal is to examine porous and poorly conducting soft materials as close as possible to their original state. This work presents a protocol for the optimization of FIB-SEM tomography parameters for porous and poorly conducting soft materials. The protocol reduces cross-sectioning artifacts, charging, and eliminates shadowing effects. In addition, it handles the subsurface and grayscale intensity overlap problems in image segmentation. The protocol was evaluated on porous polymer films which have both poor conductivity and pores. 3D reconstructions, with automated data segmentation, from three films with different porosities were successfully obtained.
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| 12. |
- Fransson, S., et al.
(författare)
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Effect of confinement and kinetics on the morphology of phase separating gelatin-maltodextrin droplets
- 2009
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:6, s. 1446-1453
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Tidskriftsartikel (refereegranskat)abstract
- The effect of confinement on the structure evolution and final morphology during phase separation and gelation of gelatin and maltodextrin was investigated and compared to the structures seen in bulk phase. Emulsion droplets with diameters from 4 to 300 ?m were analyzed using confocal laser scanning microscopy and image analysis. With the confocal laser scanning microscope it was possible to follow the entire phase separating process inside the droplets in real-time. The samples were either quenched directly from 70°C down to 20°C or exposed to holding times at 40°C. Different cooling procedures were studied to examine the structure evolution both before and after gelation in the restricted geometries. The concentration of the biopolymer mixture was kept constant at 4 w/w% gelatin and 6 w/w% maltodextrin. The results revealed that the size of the confinement had a great effect on both the initiation of phase separation and the final morphology of the microstructure inside the emulsion droplets. The phase separation in small droplets was observed to occur at a temperature above the phase separating temperature for bulk. Small droplets had either a microstructure with a shell of maltodextrin and core of gelatin or a microstructure where the two biopolymers had formed two separate bicontinuous halves. The initiation of phase separation in large droplets was similar to what was seen in bulk. The microstructure in large droplets was discontinuous, resembling the morphology in bulk phase. The kinetics had an effect on the character of the maltodextrin inclusions, as the cooling procedure of a direct quench gave spherical inclusions with an even size distribution, while a holding time at 40°C resulted in asymmetrical and elongated inclusions. © 2009 American Chemical Society.
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| 13. |
- Fransson, Sophia, 1979, et al.
(författare)
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Modelling and confocal microscopy of biopolymer mixtures in confined geometries
- 2010
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 6:12, s. 2713-2722
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of a phase separating and gelling biopolymer mixture (gelatin-maltodextrin) is strongly affected not only by thermodynamic conditions, but also by the presence of a restricted geometry. Phase separation within droplets is analysed using confocal laser scanning microscopy and image analysis by varying concentration (4% gelatin and 4%-7.3% maltodextrin), quench temperature (10 degrees C to 25 degrees C) and droplet diameters (10 mu m-120 mu m). The effects of confinement as well as quench temperature increase with increasing maltodextrin concentration in 120 mu m sized droplets. In small droplets below 20 mu m, the confinement and surface dominate the microstructure. The trends observed show good agreement with predictions of the elastic Lennard-Jones (ELJ) model, adapted to handle confinement, that is solved via conventional molecular dynamics. A one-dimensional spin-chain with variable bond length is furthermore introduced and shown to capture a number of qualitative behaviors. The findings reveal that the confined biopolymer mixture can be characterized by the very few parameters of the ELJ model, which incorporates the basic mechanism of short range attraction (collapse, crystallization) versus long range elastic repulsion (osmotic penalty). Accordingly, the study suggests that the model provides a handle towards the morphological design of binary polymer mixtures in microcapsules, droplets or other geometries of well defined size and shape.
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| 14. |
- Gmoser, Rebecca, et al.
(författare)
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Effect of dispersed particles on instant coffee foam stability and rheological properties
- 2017
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Ingår i: European Food Research and Technology. - : Springer Science and Business Media LLC. - 1438-2377 .- 1438-2385. ; 243:1, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- Properties of instant coffee foam constitute the focus of this study. The coffee, obtained from commercial sources, was dispersed in water at a concentration in the range of standard use. The resulting solution contained a substantial amount of micron and submicron size particles that were filtered with membranes having difference size cut-offs in order to investigate the relationship foam properties—particles size. The foams produced from these solutions have been imaged by confocal laser scanning microscopy, and their moduli and stability have been measured by oscillatory rheology, using an in-house developed rheometric set-up. The results show that particles larger than 0.8 µm have little effect on the reduction of drainage while a clear strengthening effect on the foam was evident. This was a result of their diffusion to the lamellae borders, which increases the viscosity of the liquid–air interface. Particles smaller than 0.2 µm affect bubble coarsening and likely hinder the migration of soluble surface active species to the bubble surface. Particles also participate in the stabilization of the air–water interface, and this affects both the foam stability and mechanical properties. Established models developed for ideal foam systems containing particles are difficult to apply due to the complexity of the system studied. Despite this limitation, these results provide increased understanding of the effect of particles on instant coffee foams.
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| 15. |
- Guillot, Gilles, 1972, et al.
(författare)
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Spatial prediction of weed intensities from exact count data and image-based estimates
- 2009
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Ingår i: Journal of the Royal Statistical Society Series C-Applied Statistics. - : Oxford University Press (OUP). - 0035-9254 .- 1467-9876. ; 58, s. 525-542
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Tidskriftsartikel (refereegranskat)abstract
- Collecting weed exact counts in an agricultural field is easy but extremely time consuming. Image analysis algorithms for object extraction applied to pictures of agricultural fields may be used to estimate the weed content with a high resolution (about 1 m(2)), and pictures that are acquired at a large number of sites can be used to obtain maps of weed content over a whole field at a reasonably low cost. However, these image-based estimates are not perfect and acquiring exact weed counts also is highly useful both for assessing the accuracy of the image-based algorithms and for improving the estimates by use of the combined data. We propose and compare various models for image index and exact weed count and we use them to assess how such data should be combined to obtain reliable maps. The method is applied to a real data set from a 30-ha field. We show that using image estimates in addition to exact counts allows us to improve the accuracy of maps significantly. We also show that the relative performances of the methods depend on the size of the data set and on the specific methodology (full Bayes versus plug-in) that is implemented.
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| 16. |
- Gårdebjer, Sofie, 1985, et al.
(författare)
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The impact of interfaces in laminated packaging on transport of carboxylic acids
- 2016
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 518, s. 305-312
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Tidskriftsartikel (refereegranskat)abstract
- The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.
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| 17. |
- Hagman, Joel H, 1983, et al.
(författare)
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Effect of Gelatin Gelation Kinetics on Probe Diffusion Determined by FRAP and Rheology
- 2010
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:12, s. 3359-3366
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Tidskriftsartikel (refereegranskat)abstract
- The time-dependent diffusion and mechanical properties of gelatin in solution, in the gel state, and during the sol/gel transition were determined using fluorescence recovery after photobleaching (FRAP) and rheology. The parameters in the experimental design were 2% w/w and 5% w/w gelatin concentration; 15, 20, and 25 degrees C end quench temperatures; and Na-2-fluorescein, 10 kDa FITC-dextran, and 500 kDa FITC-dextran as diffusion probes. The samples were monitored in solution at 60 degrees C, during quenching, for 75 min at end quench temperatures and after 1, 7, and 14 days of storage at the end quench temperature. The effect of temperature on the probe diffusion was normalized by determining the free diffusion of the probes in pure water for the different temperatures. The results gained by comparing FRAP and rheology showed that FRAP is able to capture structural changes in the gelatin before gelation occurs, which was interpreted as a formation of transient networks. This was clearly seen for 2% w/w gelatin and 20 and 25 degrees C end quench temperatures. The structural changes during sol/gel transition are detected only by the larger probes, giving information about the typical length scales in the gelatin structure. The normalized diffusion rate increased after 7 and 14 days of storage. This increase was most pronounced for fluorescein but was also seen for the larger probes.
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| 18. |
- Hagman, Joel H, 1983, et al.
(författare)
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Probe diffusion in κ-carrageenan gels determined by fluorescence recovery after photobleaching
- 2012
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 29:1, s. 106-115
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Tidskriftsartikel (refereegranskat)abstract
- The effects of free volume and heterogeneity on probe diffusion in κ-carrageenan gels were determined by fluorescence recovery after photobleaching (FRAP) and rheology. By changing the ionic conditions, biopolymer concentration and end temperature, different microstructures and aggregation kinetics in the κ-carrageenan gels were evaluated. The results of the FRAP measurements were compared to transmission electron microscopy (TEM) and nuclear magnetic resonance diffusometry (NMRd) data from previous studies. The results showed that the free diffusion rates of the probe (FITC dextran) in water were influenced by both temperature and ionic conditions. The free diffusion values were used for normalization of the diffusion rates in the κ-carrageenan gel measurements. The compatibility between FITC dextran with different molecular weights (10 and 500 kDa) and κ-carrageenan was evaluated. The results showed that the larger FITC dextran probe phase separates; therefore only the 10 kDa FITC dextran probe was used in the FRAP experiments. FRAP measurements and NMRd probe diffusion in combination with TEM in κ-carrageenan revealed that the void space, degree of aggregation and heterogeneity influence the probe diffusion rate. The κ-carrageenan gelation was analyzed at different end temperatures using rheology and FRAP. The FITC dextran probe diffusion was not influenced by κ-carrageenan aggregation, regardless of rheological gelation kinetics and storage modulus near the gel point. This indicates that the average void space between the gel strands is larger than the size of the probe. Good correlation between the microstructure and the probe diffusion rate in κ-carrageenan gel with different ionic conditions and constant biopolymer concentration were obtained with TEM and FRAP.
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| 19. |
- Hagsten, Carin, et al.
(författare)
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Composition and structure of high temperature dairy fouling
- 2016
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Ingår i: Food Structure. - : Elsevier BV. - 2213-3291. ; 7, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- The fouling structure and composition is dependent on the product, but also on the heating process applied to it. The structure will have profound effect on the cleaning process and the down time in the production plant. Here, the structure of high temperature (137 °C) milk fouling has been investigated, which so far has not been sufficiently studied in a systematic way. This particular fouling has a high content of the mineral calcium phosphate and a relatively low concentration of protein. Wide angle X-ray diffraction (WAXD) reveals a crystalline structure of calcium phosphate in agreement to the chemical analysis of the bulk layer. Microscopic investigations visualize the heterogeneous structure and energy dispersive X-ray spectroscopy (EDX) shows a spatial variation of the elements through the radius of the sample.
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| 20. |
- Hagsten, Carin, et al.
(författare)
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Structural and compositional changes during UHT fouling removal-Possible mechanisms of the cleaning process
- 2019
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Ingår i: Food Structure. - : Elsevier BV. - 2213-3291. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-high temperature (UHT) treatment of milk forms a deposit or fouling in the processing equipment that is mineral-based with an enclosed protein network. This study addresses the fundamental mechanisms that control the removal of this deposit. For this purpose, the structural and compositional changes during the cleaning process have been studied. The structure analysis was performed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) on samples that were quenched at different stages of the cleaning process. It was found for acid cleaning that the mineral content is rapidly decreasing in the fouling layer as the cleaning continues, but there is still an intact protein structure with the similar thickness as the original fouling. For alkali cleaning, part of the protein structure was subsequently removed from the outside towards the stainless steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolyrnerization of protein aggregates, were found to control the cleaning efficiency. The weakening of the protein network facilitates the removal of the UHT fouling layer during the acid cleaning step and allow for an efficient cleaning cycle. The chemical reactions that occur within the fouling layer between the hydroxyl ions and the protein network was modeled according to a depolymerization reaction and a mechanistic model of the cleaning process is presented.
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| 21. |
- Hamngren Blomqvist, Charlotte, 1984, et al.
(författare)
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Interconnectivity imaged in three dimensions : Nano-particulate silica-hydrogel structure revealed using electron tomography
- 2017
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Ingår i: Micron. - : Elsevier BV. - 0968-4328 .- 1878-4291. ; 100, s. 91-105
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Tidskriftsartikel (refereegranskat)abstract
- We have used Electron Tomography (ET) to reveal the detailed three-dimensional structure of particulate hydrogels, a material category common in e.g. controlled release, food science, battery and biomedical applications. A full understanding of the transport properties of these gels requires knowledge about the pore structure and in particular the interconnectivity in three dimensions, since the transport takes the path of lowest resistance. The image series for ET were recorded using High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). We have studied three different particulate silica hydrogels based on primary particles with sizes ranging from 3.6 nm to 22 nm and with pore-size averages from 18 nm to 310 nm. Here, we highlight the nanostructure of the particle network and the interpenetrating pore network in two and three dimensions. The interconnectivity and distribution of width of the porous channels were obtained from the three-dimensional tomography studies while they cannot unambiguously be obtained from the two-dimensional data. Using ET, we compared the interconnectivity and accessible pore volume fraction as a function of pore size, based on direct images on the nanoscale of three different hydrogels. From this comparison, it was clear that the finest of the gels differentiated from the other two. Despite the almost identical flow properties of the two finer gels, they showed large differences concerning the accessible pore volume fraction for probes corresponding to their (two-dimensional) mean pore size. Using 2D pore size data, the finest gel provided an accessible pore volume fraction of over 90%, but for the other two gels the equivalent was only 10–20%. However, all the gels provided an accessible pore volume fraction of 30–40% when taking the third dimension into account.
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| 22. |
- Hamngren Blomqvist, Charlotte, 1984, et al.
(författare)
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Pore size effects on convective flow and diffusion through nanoporous silica gels
- 2015
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 484, s. 288-296
-
Tidskriftsartikel (refereegranskat)abstract
- Material structure has great impact on mass transport properties, a relationship that needs to be understood on several length scales. Describing and controlling the properties of flow through soft materials are both challenges concerning the industrial use of gel structures. This paper reports on how the porous structure in nanoporous materials affects the water transport through them. We used three different silica gels with large differences in the pore sizes but of equal silica concentration. Particle morphology and gel structure were studied using high-resolution transmission electron microscopy and image analysis to estimate the pore size distribution and intrinsic surface area of each gel. The mass transport was studied using a flow measurement setup and nuclear magnetic resonance diffusometry. The average pore size ranged from approximately 500. nm down to approximately 40. nm. An acknowledged limit for convective flow to occur is in the pore size range between 100 and 200. nm. The results verified the existence of a non-linear relationship between pore size and liquid flow at length scales below 500. nm, experimentally. A factor of 4.3 in flow speed separated the coarser gel from the other two, which presented almost identical flow speed data despite a factor 3 in pore size difference. In the setup, the mass transport in the gel with the largest pores was flow dominated, while the mass transport in the finer gels was diffusion dominated. Besides providing new insights into mass transport as a function of pore sizes, we conclude that three-dimensional analysis of the structures is needed for a comprehensive understanding of the correlation between structure and mass transport properties.
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| 23. |
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| 24. |
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| 25. |
- Jonasson, Jenny, 1976, et al.
(författare)
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A pixel-based likelihood framework for analysis of fluorescence recovery after photobleaching data
- 2008
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 232:2, s. 260-269
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Tidskriftsartikel (refereegranskat)abstract
- A new framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM) is presented. It is a pixel-based statistical methodology that efficiently utilizes all information about the diffusion process in the available set of images. The likelihood function for a series of images is maximized which gives both an estimate of the diffusion coefficient and a corresponding error. This framework opens up possibilities (1) to obtain localized diffusion coefficient estimates in both homogeneous and heterogeneous materials, (2) to account for time differences between the registrations at the pixels within each image, and (3) to plan experiments optimized with respect to the number of replications, the number of bleached regions for each replicate, pixel size, the number of pixels, the number of images in each series etc. To demonstrate the use of the new framework, we have applied it to a simple system with polyethylene glycol (PEG) and water where we find good agreement with diffusion coefficient estimates from NMR diffusometry. In this experiment, it is also shown that the effect of the point spread function is negligible, and we find fluorochrome-concentration levels that give a linear response function for the fluorescence intensity. © 2008 The Authors.
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| 26. |
- Jonasson, Jenny, 1976, et al.
(författare)
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Pixel-based analysis of FRAP data with a general initial bleaching profile
- 2010
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 239:2, s. 142-153
-
Tidskriftsartikel (refereegranskat)abstract
- Jonasson et al. (2008), we presented a new pixel-based maximum likelihood framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM). The main method there, called the Gaussian profile method below, is based on the assumption that the initial intensity profile after photobleaching is approximately Gaussian. In the present paper, we introduce a method, called the Monotone profile method, where the maximum likelihood framework is extended to a general initial bleaching profile only assuming that the profile is a non-decreasing function of the distance to the bleaching centre. The statistical distribution of the image noise is further assumed to be Poisson instead of normal, which should be a more realistic description of the noise in the detector. The new Monotone profile method and the Gaussian profile method are applied to FRAP data on swelling of super absorbent polymers (SAP) in water with a Fluorescein probe. The initial bleaching profile is close to a step function at low degrees of swelling and close to a Gaussian profile at high degrees of swelling. The results obtained from the analysis of the FRAP data are corroborated with NMR diffusometry analysis of SAP with a polyethylene glycol probe having size similar to the Fluorescein. The comparison of the Gaussian and Monotone profile methods is also performed by use of simulated data. It is found that the new Monotone profile method is accurate for all types of initial profiles studied, but it suffers from being computationally slow. The fast Gaussian profile method is sufficiently accurate for most of the profiles studied, but underestimates the diffusion coefficient for profiles close to a step function. We also provide a diagnostic plot, which indicates whether the Gaussian profile method is acceptable or not.
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| 27. |
- Karlsson, Kristina, 1988, et al.
(författare)
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Extrusion Parameters for Foaming of a β-Glucan Concentrate
- 2019
-
Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919. ; 27:6, s. 1167-1177
-
Tidskriftsartikel (refereegranskat)abstract
- Plastics is a group of materials commonly encountered on a daily basis by many people. They have enabled rapid, low-cost manufacturing of products with complicated geometries and have contributed to the weight reduction of heavy components, especially when produced into a foamed structure. Despite the many advantages of plastics, some drawbacks such as the often fossil-based raw-material and the extensive littering of the material in nature, where it is not degraded for a very long time, needs to be dealt with. One way to address at least one of the issues could be to use polymers from nature instead of fossil-based ones. Here, a β-glucan concentrate originating from barley was investigated. The concentrate was processed into a foam by hot-melt extrusion, and the processing window was established. The effect of different blowing agents was also investigated. Water or a combination of water and sodium bicarbonate were used as blowing agents, the latter apparently giving a more uniform pore structure. The porous structure of the foamed materials was characterized mainly by using a combination of confocal laser scanning microscope and image analysis. The density of the samples was estimated and found to be in a similar range as some polyurethane foams. A set of 3D parameters were also quantified on two selected samples using X-ray microtomography in combination with image analysis, where it was indicated that the porous structure had a pre-determined direction, which followed the direction of the extrusion process. © 2019, The Author(s).
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| 28. |
- Kvarnström, Mats, 1974, et al.
(författare)
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Brownian dynamics simulations in hydrogels using an adaptive time-stepping algorithm
- 2009
-
Ingår i: Physical Review E. - 2470-0045 .- 2470-0053. ; 79:1, s. 16102-
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Tidskriftsartikel (refereegranskat)abstract
- The adaptive time-stepping algorithm for Brownian simulation of solute diffusion in three-dimensional complex geometries previously developed by the authors of this paper was applied to heterogeneous three-dimensional polymer hydrogel structures. The simulations were performed on reconstructed three-dimensional hydrogels. The obstruction effect from the gel strands on water and diffusion of dendrimers with different sizes were determined by simulations and compared with experimental nuclear magnetic resonance diffusometry data obtained from the same material. It was concluded that obstruction alone cannot explain the observed diffusion rates, but an interaction between the dendrimers and the gel strands should be included in the simulations. The effect of a sticky-wall interaction potential with geometrically distributed residence times on the diffusion rate has been studied. It was found that sticky-wall interaction is a possible explanation for the discrepancy between simulated and experimental diffusion data for dendrimers of different sizes diffusing in hydrogels.
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| 29. |
- Kvist, Patric, et al.
(författare)
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Using fluorescent probes and FRAP to investigate macromolecule diffusion in steam-exploded wood
- 2018
-
Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 0043-7719 .- 1432-5225. ; 52:5, s. 1395-1410
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion of fluorescently labeled dextran of varying molecular weight in wood pretreated by steam explosion was studied with a confocal microscope. The steam explosion experiments were conducted at relatively mild conditions relevant for materials biorefinery at a pressure of 14 bars for 10 min. The method of fluorescence recovery after photobleaching (FRAP) was used to perform diffusion measurements locally in the wood microstructure. It was found that the FRAP methodology can be used to observe differences in the diffusion coefficient based on localization in the microstructure, i.e., earlywood, latewood, and cell wall. Microscopic changes due to steam explosion were seen to increase diffusion of the smaller 3-kDa dextran diffusion probe in the earlywood, while the latewood structure was not affected in any significant way. Macroscopic changes to the structure in the form of ruptures due to the steam explosion pretreatment were observed to increase the rate of diffusion for the larger 40-kDa dextran probe.
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| 30. |
- Longfils, Marco, 1990, et al.
(författare)
-
Raster Image Correlation Spectroscopy Performance Evaluation
- 2019
-
Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 117:10, s. 1900-1914
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Tidskriftsartikel (refereegranskat)abstract
- Raster image correlation spectroscopy (RICS) is a fluorescence image analysis method for extracting the mobility, concentration, and stoichiometry of diffusing fluorescent molecules from confocal image stacks. The method works by calculating a spatial correlation function for each image and analyzing the average of those by model fitting. Rules of thumb exist for RICS image acquisitioning, yet a rigorous theoretical approach to predict the accuracy and precision of the recovered parameters has been lacking. We outline explicit expressions to reveal the dependence of RICS results on experimental parameters. In terms of imaging settings, we observed that a twofold decrease of the pixel size, e.g., from 100 to 50 nm, decreases the error on the translational diffusion constant (D) between three- and fivefold. For D = 1 mu m(2) s(-1), a typical value for intracellular measurements, similar to 25-fold lower mean-squared relative error was obtained when the optimal scan speed was used, although more drastic improvements were observed for other values of D. We proposed a slightly modified RICS calculation that allows correcting for the significant bias of the autocorrelation function at small (<<50 x 50 pixels) sizes of the region of interest. In terms of sample properties, at molecular brightness E = 100 kHz and higher, RICS data quality was sufficient using as little as 20 images, whereas the optimal number of frames for lower E scaled pro rata. RICS data quality was constant over the nM-mM concentration range. We developed a bootstrap-based confidence interval of D that outperformed the classical leastsquares approach in terms of coverage probability of the true value of D. We validated the theory via in vitro experiments of enhanced green fluorescent protein at different buffer viscosities. Finally, we outline robust practical guidelines and provide free software to simulate the parameter effects on recovery of the diffusion coefficient.
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| 31. |
- Longfils, Marco, 1990, et al.
(författare)
-
Single particle raster image analysis of diffusion
- 2017
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 266:1, s. 3-14
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Tidskriftsartikel (refereegranskat)abstract
- As a complement to the standard RICS method of analysing Raster Image Correlation Spectroscopy images with estimation of the image correlation function, we introduce the method SPRIA, Single Particle Raster Image Analysis. Here, we start by identifying individual particles and estimate the diffusion coefficient for each particle by a maximum likelihood method. Averaging over the particles gives a diffusion coefficient estimate for the whole image. In examples both with simulated and experimental data, we show that the new method gives accurate estimates. It also gives directly standard error estimates. The method should be possible to extend to study heterogeneous materials and systems of particles with varying diffusion coefficient, as demonstrated in a simple simulation example. A requirement for applying the SPRIA method is that the particle concentration is low enough so that we can identify the individual particles. We also describe a bootstrap method for estimating the standard error of standard RICS.
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| 32. |
- Longfils, Marco, 1990, et al.
(författare)
-
Single particle raster image analysis of diffusion for particle mixtures
- 2018
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 269:3, s. 269-281
-
Tidskriftsartikel (refereegranskat)abstract
- Recently we complemented the raster image correlation spectroscopy (RICS) method of analysing raster images via estimation of the image correlation function with the method single particle raster image analysis (SPRIA). In SPRIA, individual particles are identified and the diffusion coefficient of each particle is estimated by a maximum likelihood method. In this paper, we extend the SPRIA method to analyse mixtures of particles with a finite set of diffusion coefficients in a homogeneous medium. In examples with simulated and experimental data with two and three different diffusion coefficients, we show that SPRIA gives accurate estimates of the diffusion coefficients and their proportions. A simple technique for finding the number of different diffusion coefficients is also suggested. Further, we study the use of RICS for mixtures with two different diffusion coefficents and investigate, by plotting level curves of the correlation function, how large the quotient between diffusion coefficients needs to be in order to allow discrimination between models with one and two diffusion coefficients. We also describe a minor correction (compared to published papers) of the RICS autocorrelation function. Lay description Diffusion is a key mass transport mechanism for small particles. Efficient methods for estimating diffusion coefficients are crucial for analysis of microstructures, for example in soft biomaterials. The sample of interest may consist of a mixture of particles with different diffusion coefficients. Here, we extend a method called Single Particle Raster Image Analysis (SPRIA) to account for particle mixtures and estimation of the diffusion coefficients of the mixture components. SPRIA combines elements of classical single particle tracking methods with utilizing the raster scan with which images obtained by using a confocal laser scanning microscope. In particular, single particles are identified and their motion estimated by following their center of mass. Thus, an estimate of the diffusion coefficient will be obtained for each particle. Then, we analyse the distribution of the estimated diffusion coefficients of the population of particles, which allows us to extract information about the diffusion coefficients of the underlying components in the mixture. On both simulated and experimental data with mixtures consisting of two and three components with different diffusion coefficients, SPRIA provides accurate estimates and, with a simple criterion, the correct number of mixture components is selected in most cases.
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| 33. |
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| 34. |
- Loren, Niklas, et al.
(författare)
-
Confocal fluorescence microscopy (CLSM) for food structure characterisation
- 2007
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Ingår i: Understanding and Controlling the Microstructure of Complex Foods. - : Elsevier. ; , s. 232-260
-
Tidskriftsartikel (refereegranskat)abstract
- * Introduction * Principles of modern CLSM * CLSM and the study of food structure * Application of CLSM to food systems * Measuring and modelling using CLSM images * Conclusions and future trends * References. © 2007 Woodhead Publishing Limited. All rights reserved.
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| 35. |
- Loren, Niklas, et al.
(författare)
-
Confocal laser scanning microscopy and image analysis of kinetically trapped phase-separated gelatin/maltodextrin gels
- 1999
-
Ingår i: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 13:2, s. 185-198
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of phase separation on the gelatin/maltodextrin systems has been studied using confocal laser scanning microscopy and image analysis. Stereological image analysis has been used to analyse the effect of different cooling rates, holding times, holding temperatures and gelatin types on the microstructure at pH 5.3. The quantified microstructural parameters were the volume-weighted mean volume, the interfacial area and the area fraction. A factorial experimental design was used, with cooling rate (0.2°C/min, 1°C/min, 10°C/min), holding time (0 min, 10 min, 20 min), holding temperature (20°C, 25°C, 30°C), and two different gelatin types (LH, PS) as design parameters. Gelatin lime hide (LH) has an isoelectric point of pH 4.7, and gelatin pig skin (PS), has an isoelectric point of pH 9.1. The composition was kept constant at 4% gelatin and 5% maltodextrin. The results showed that the phase-separated system was gelatin continuous. The size of the maltodextrin inclusions decreases with increasing cooling rate and was largest at the lowest cooling rate (0.2°C/min). Gelatin PS has larger maltodextrin inclusions and a smaller interfacial area than gelatin LH. The size of the maltodextrin inclusions varied in diameter between 3 and 10 ?m for gelatin LH and between 3 and 18 ?m for gelatin PS. The size of the maltodextrin inclusions increases with increasing holding time and was largest at 20 min. The interfacial area increases with increasing cooling rates and was largest at 10°C/min. A region was found where the phase separation and the gel formation competed with each other in connection with mobility. The residence time in that region and how fast the sample proceeds through it, are important for the morphology of the resulting microstructure. © 1999 Elsevier Science Ltd.
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| 36. |
- Loren, Niklas, et al.
(författare)
-
Dendrimer diffusion in ?-carrageenan gel structures
- 2009
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:2, s. 275-284
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of the ?-carrageenan concentration on gel microstructure and self-diffusion of polyamideamine dendrimers has been determined by transmission electron microscopy (TEM), image analysis, and nuclear magnetic resonance (NMR) diffusometry. Different salt conditions of KCl, NaCl, and mixtures thereof allowed for formation of significantly different microstructures. The ?-carrageenan concentrations were varied between 0.25 and 3.0 w/w% for a salt mixture containing 20 mM KCl and 200 mM NaCl gels and between 0.5 and 4.0 w/w% for 250 mM NaCl gels. Furthermore, the effect of potassium ion concentration on the gel structure and the dendrimer diffusion rate was determined. The potassium ion concentration was varied between 20 mM KCl and 200 mM KCl. Two different dendrimer generations with significant difference in size were used: G2 and G6. Dendrimers were found to be sensitive probes for determination of the effect of the gel microstructure on molecular diffusion rate. A qualitative comparison between TEM micrographs, NMR diffusometry data and image analysis showed that the gel structure has a large impact on the dendrimers diffusion in ?-carrageenan gels. It was found that diffusion was strongly influenced by the ?-carrageenan concentration and the dendrimer generation. Small voids in the gel network gave strongly reduced diffusion. Image analysis revealed that the interfacial area between the gel network and the surrounding water phase correlated well with the dendrimer diffusion. © 2009 American Chemical Society.
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| 37. |
- Loren, Niklas, et al.
(författare)
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Determination of local diffusion properties in heterogeneous biomaterials
- 2009
-
Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686 .- 1873-3727. ; 150:1, s. 42139-
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Tidskriftsartikel (refereegranskat)abstract
- The coupling between structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. Structural heterogeneity is defined and its implications for time-dependent diffusion are discussed in detail. The effect of structural heterogeneity in biomaterials on diffusion and the relevance of length scales are exemplified with regard to different biomaterials such as gels, emulsions, phase separated biopolymer mixtures and chocolate. Different diffusion measurement techniques for determination of diffusion properties at different length and time scales are presented. The interplay between local and global diffusion is discussed. New measurement techniques have emerged that enable simultaneous determination of both structure and local diffusion properties. Special emphasis is given to fluorescence recovery after photobleaching (FRAP). The possibilities of FRAP at a conceptual level is presented. The method of FRAP is briefly reviewed and its use in heterogeneous biomaterials, at barriers and during dynamic changes of the structure is discussed. © 2009 Elsevier B.V. All rights reserved.
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| 38. |
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| 39. |
- Lorén, Niklas, 1970, et al.
(författare)
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Fluorescence recovery after photobleaching in material and life sciences: Putting theory into practice
- 2015
-
Ingår i: Quarterly Reviews of Biophysics. - 1469-8994 .- 0033-5835. ; 48:3, s. 323-387
-
Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2015 Cambridge University Press.Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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| 40. |
- Loren, Niklas, et al.
(författare)
-
Measuring shapes for application in complex food structures
- 2006
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 20:5, s. 712-722
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Tidskriftsartikel (refereegranskat)abstract
- The image analysis method of Fourier shape description is implemented to analyse shaped food microstructural entities, independent of their complexity, because entity shape is an important and nearly unexploited possibility for designing food material properties. The method is described in four steps: the accuracy of image acquisition, representation of the object outline, calculation of components and interpretation of the components, all focusing on colloidal food system applications. Three different common food systems are used to emphasise the possibilities that Fourier shape description offers for food structure design and food processing. Fourier shape measurements make it possible to quantify, present a typical shape and determine the distribution of shape independently of size of model food suspension consisting of complex shaped entities. This was done in an automatic and replicable way. The time evolution of entities structured in a flow field during model processing is analysed using Fourier shape descriptors. Graphs of time-dependent, low order single Fourier components allow control of the entity shape during processing. Differences in the shape of water domains in heterogeneous emulsions are quantified and classified on different length scales using a multivariate hypothesis test. © 2005 Elsevier Ltd. All rights reserved.
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| 41. |
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| 42. |
- Loren, Niklas, et al.
(författare)
-
Phase separation induced by conformational ordering of gelatin in gelatin/maltodextrin mixtures
- 2001
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 34:2, s. 289-297
-
Tidskriftsartikel (refereegranskat)abstract
- Mixtures of gelatin and maltodextrin in aqueous solution have been quenched to temperatures at which they are initially miscible but where gelatin ordering is initiated. In many cases phase separation was observed to occur after a significant time delay, and the dependence of these delays on quench temperature and biopolymer concentration has been studied in detail using turbidity measurements and confocal laser scanning microscopy (CLSM). Furthermore, by observing the optical rotation (OR) and turbidity of the system simultaneously, the gelatin helix content and the time delay before the onset of phase separation were monitored concurrently. The observed delay times were found to correspond to the time taken for the development of a certain degree of gelatin ordering, which drives the separation process. A further consequence of gelatin ordering is the viscosifying of the solution and, at sufficient concentrations, the formation of a gel. Therefore, rheological measurements have been used in addition to turbidity measurements and CLSM in order to monitor further the structural development of the systems. A comparison of the data obtained from these techniques shows that while the development of a certain elasticity will trap the system morphology, this elasticity is not directly related to that found at the gel point. At low maltodextrin concentrations, where phase separation was not detected by turbidity, transmission electron microscopy (TEM) has been used to examine the microstructure on a smaller length scale.
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| 43. |
- Loren, Niklas, et al.
(författare)
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Sodium reduction in foods : Challenges and strategies for technical solutions
- 2023
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Ingår i: Journal of Food Science. - : John Wiley and Sons Inc. - 0022-1147 .- 1750-3841. ; 88:3, s. 885-
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Tidskriftsartikel (refereegranskat)abstract
- In many parts of the world, sodium consumption is higher than recommended levels, representing one of the most important food-related health challenges and leading to considerable economical costs for society. Therefore, there is a need to find technical solutions for sodium reduction that can be implemented by food producers and within food services. The aims of this review are to discuss the barriers related to sodium reduction and to highlight a variety of technical solutions. The barriers relate to consumer perception, microbiology, processing, and physicochemistry. Existing technical solutions include inhomogeneous salt distribution, coated salt particles, changing particle sizes and forms, surface coating, multisensory combinations, sodium replacements, double emulsions, adapted serum release by microstructure design, and adapted brittleness by microstructure design. These solutions, their implementation and the associated challenges, and applicable product categories are described. Some of these solutions are ready for use or are in their early development stages. Many solutions are promising, but in most cases, some form of adaptation or optimization is needed before application in specific products, and care must always be taken to ensure food safety. For instance, further research and innovation are required in the dynamic evolution of saltiness perception, consumer acceptance, the binding and migration of sodium, juiciness, microbiological safety, and the timing of salt addition during processing. Once implemented, these solutions will undoubtedly support food producers and food services in reducing sodium content and extend the application of the solutions to different foods. © 2022 Research Institutes of Sweden, Swedish Food Federation and Lyckeby Culinar AB.
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| 44. |
- Loren, Niklas, et al.
(författare)
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Structure evolution during gelation at later stages of spinodal decomposition in gelatin/maltodextrin mixtures
- 2001
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 34:23, s. 8117-8128
-
Tidskriftsartikel (refereegranskat)abstract
- The kinetics of phase separation and gelation in kinetically trapped gelatin/maltodextrin/water gels was studied using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). The time evolution of the morphology was followed by CLSM during temperature quenches from 60°C to between 1 and 40°C. The maltodextrin concentration was varied between 2.25% and 7.5% (w/w), and the gelatin concentration was held constant at 4% (w/w). Spinodal decomposition, self-similar growth, percolation-to-cluster transition, coalescence, and diffusion of maltodextrin inclusions were observed during the progress of gelation. The start and completion of these processes, the onset of phase separation, and the relative rates of phase separation and gelation were found to determine the morphology. The characteristic wavelength showed a crossover in its growth rate power law from one-third to one in a slowly gelling, near-symmetric system. Droplet and bicontinuous morphologies were observed in off-symmetric and near-symmetric quenches, respectively. Secondary phase separation occurred at low temperatures and near-symmetric composition. Partial coalescence and contracted flocculation were observed during the progress of gelation. Stereological measurements showed that the size of maltodextrin inclusions increases and that the volume fraction decreases with increasing quench temperature. In addition, the number of the maltodextrin inclusions decreases with increasing quench temperature.
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| 45. |
- Lorén, Niklas, 1970
(författare)
-
Structure Evolution during Phase Separation and Gelation of Biopolymer Mixtures
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the kinetics of phase separation and gelation in aqueous mixtures of gelatin and maltodextrin. The structure evolution of these mixtures at different length scales was recorded by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). The microstructure was quantified by image analysis. All mixtures phase separated during cooling into the incompatible region of the phase diagram. The main conclusion of this work is that it is possible to control the final microstructure of mixed biopolymer systems by the kinetics of phase separation and gelation, which can lead to new materials with unique properties in the future. The work shows that the phase separation was kinetically trapped by the gelation in a non-equilibrium situation. The final morphology was determined by the relative rates of phase separation and gelation, the onset of phase separation and gelation, and the gelation context in which the phase separation proceeded. The phase separation processes involve self-similar growth, percolation-to-cluster transition, coalescence, secondary phase separation and sedimentation. Start, stop, rate and which of these processes are involved in the time evolution of the microstructure in relation to the rate and progress of the gelation determine the final morphology. The phase separation mechanisms and the energetically most favourable growing wavelength in the early stage of spinodal decomposition strongly affected the final morphology. Another interesting result was that it was possible to determine the phase separation mechanism by comparing the time evolution of the microstructure with existing theories about the kinetics of phase separation and coarsening. Three kinetic zones were established according to the size of the maltodextrin inclusions and the temperature of phase separation. The kinetic zones were an effect of the relative rates of phase separation and gelation. It was generally found that the size of the maltodextrin inclusions increases with an increasing phase separation temperature, a decreasing cooling rate, an increasing maltodextrin concentration and an increasing end temperature. The conformational ordering of gelatin gives an extra incentive for phase separation, which results in increased incompatibility of the mixture with time. It was found that the gelation can trap the coalescence in intermediate stages, resulting in partial coalescence and contracted flocculation. In the end state, after the microstructure has been trapped by the gelation, small maltodextrin inclusions can migrate towards the larger inclusions and the gelatin network becomes more uniform. Turbidity and rheological measurements showed that several hundred Pascals are required to trap the microstructure, and the gel point does not necessarily reflect this trapping. A crossover from diffusive growth to hydrodynamic growth was found in bicontinuous microstructures. The growth rate after the crossover, and the increase of the peak intensity with time were found to increase with increasing quench depth at constant composition. The dimensionality of the growth was three and the time evolution of the microstructure obeyed dynamical scaling in both the intermediate and late stages of spinodal decomposition.
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| 46. |
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| 47. |
- Loren, Niklas, et al.
(författare)
-
Water mobility in heterogeneous emulsions determined by a new combination of confocal laser scanning microscopy, image analysis, nuclear magnetic resonance diffusometry, and finite element method simulation
- 2005
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 122:2, s. 24716-
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear magnetic resonance (NMR) diffusometry and confocal laser scanning microscopy (CLSM) were combined in a quantitative way in finite element calculations of water propagation in CLSM images obtained from a very heterogeneous emulsion. The propagators calculated on the basis of microstructure were Fourier transformed and subsequently compared with the echo decays obtained by the NMR diffusometry method. The results showed very good agreement between microstructure based calculations and experiments, indicating that the short gradient pulse approximation in the NMR diffusometry experiment holds for a certain q range. Furthermore, the CLSM was able to achieve a relevant two-dimensional microstructure although some discrepancy at low q values was noted. This effect is attributed to the inherent three-dimensional connectivity between the water domains in this type of structures, making the calculations slightly underestimate the water diffusion at longer distances. © 2005 American Institute of Physics.
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| 48. |
- Lundell, C., et al.
(författare)
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Influence of elongational flow on phase separated inclusions within gelling biopolymer drops
- 2004
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 18:5, s. 805-815
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Tidskriftsartikel (refereegranskat)abstract
- Drops of an immiscible biopolymer mixture containing maltodextrin/gelatine were shaped and set in an elongational flow in a flow cell called 4-RM. The kinetics of phase separation as well as the kinetics of gel formation were governed by the temperature differences which appear as the 60°C maltodextrin/gelatine mixture reaches the 10°C silicon oil in the 4-RM. The shape and inner structure of the drops were visualized with the help of a confocal laser scanning microscope (CLSM). The result showed that the solution phase separated into gelatine-rich and a maltodextrin-rich phase during the short time it takes to gel the particle, i.e. in approximately 2 s. It was found that the shape of the phase separated inclusions was affected by the elongational flow. Mixtures of a 10% constant gelatine concentration and a 2-15% maltodextrin concentration were evaluated. The size of the inclusions within the phase separated drops increases as the maltodextrin concentration increases. At a maltodextrin concentration of 12%, the phase inversion has occurred. Shape transfer between the drop and its inclusions was investigated. The length to width ratios of the drops and its inclusions were compared and it was found that for the gelatine-continuous drop created at a flow rate of 10 rpm the ratio responds well. A comparison of the Taylor parameter calculated from viscosity data before gel formation and image analysis of experimental results showed that deformation takes place within the critical stage of gel formation. © 2004 Elsevier Ltd. All rights reserved.
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| 49. |
- Mohlin, Kristina, 1970, et al.
(författare)
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Water pores in alkyl ketene dimer (AKD) dispersions studied by NMR diffusometry and optical microscopy
- 2007
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 297:1-3, s. 114-121
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Tidskriftsartikel (refereegranskat)abstract
- Water borne alkyl ketene dimer (AKD) dispersions have been investigated by means of optical microscopy and NMR diffusometry (NMR-D). In two different formulations, different amounts of entrapped water in pores with different sizes are obtained, which can be compared to a waterin-oil-in-water (w/o/w) dispersion. It is shown that the amount of entrapped water inside the AKD particles can conveniently be measured with the NMR-D technique. The pore size is however not obtained correctly from the NMR-D experiment. Due to the small size of the water pores, the pore size is underestimated when measured with NMR-D. This effect is investigated in more detail by Brownian dynamic simulations from which a correction factor is obtained that allows a more correct value of the pore size from NMR-D measurements. When the pore size is too small to be observed by optical microscopy, typically below 0.5 mu m, NMR diffusometry combined with Brownian dynamic simulations are shown to be a rapid and reliable tool for quantifying the porosity in these types of systems.
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| 50. |
- Niimi, Jun, et al.
(författare)
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Saltiness enhancement : Impact of acid added to bread with heterogeneously distributed sodium chloride
- 2023
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Ingår i: Lebensmittel-Wissenschaft + Technologie. - : Academic Press. - 0023-6438 .- 1096-1127. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- The current global sodium consumption exceeds recommended daily intakes and there is a great need to reduce the sodium content in foods for a healthier society. The current study investigated the effect of combining sensory interaction principles and heterogeneous distribution of NaCl in bread on sensory properties, structure, and NaCl distribution. Breads were prepared in three different arrangements of NaCl distribution: homogenous, layered, and layered with lactic acid. Within each arrangement, four NaCl levels were tested. The breads were evaluated by a sensory panel for perceived saltiness, sourness, and qualitative texture, measured for stiffness, and the NaCl distribution was determined by X-ray fluorescence microscopy (XFM). Perceived saltiness was significantly enhanced in breads beyond heterogeneous NaCl distribution when lactic acid was added. Stiffness measurements were affected by layering of bread, the layers without NaCl were stiffer with an increase in overall salt concentration. The heterogeneous distribution of NaCl in layered breads could be visualised by XFM and textural consequences of layering bread are discussed. The current study demonstrates the potential of combining principles of pulsation of taste and sensory interactions together to enhance salt perception, and hence suggesting the approach as a possible further strategy for NaCl reduction in bread.
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