| 1. |
- Falk, Yana Znamenskaya, et al.
(författare)
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Effects of Hydration on Structure and Phase Behavior of Pig Gastric Mucin Elucidated by SAXS
- 2018
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 122:30, s. 7539-7546
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Tidskriftsartikel (refereegranskat)abstract
- In this work small-angle X-ray scattering (SAXS) was used to study hydration and temperature-induced changes of pig gastric mucin (PGM) within the entire concentration range. The scattering is interpreted as originating from PGM fiber-like structures that adopt rod-like bottle-brush conformation in dilute solutions. On the basis of the knowledge about molecular structure of mucins and SAXS data for dilute solutions, we propose a theoretical model for predicting mucin conformation in solution and calculate the corresponding scattering profile. This bottle-brush model comprises a protein backbone with carbohydrate side chains and corresponding structural parameters, such as grafting distance and lengths of the backbone and side chains. It describes the experimental PGM data from dilute solutions in the full q range very well. It furthermore suggests that the carbohydrate side chains are grafted with a regular separation of around 5 nm and a length of 14 nm. The cross-section size with a radius of about 1 nm is also in accordance with the size of the carbohydrate units. Structuring of PGM solutions at higher concentrations was investigated by analyzing semidilute and concentrated PGM samples. Starting at about 20 wt %, Bragg peaks become clearly visible indicating a more ordered mucin system. In very dehydrated and fully dry mucin samples these peaks are not present indicating lack of long-range order. The SAXS data show that the structural change occurring at about 80 wt % mucin and 25 degrees C corresponds to a glass transition in agreement with our previous calorimetric results. Temperature also has an effect on the phase behavior of mucin. At intermediate levels of hydration, a phase transition is observed at about 60-70 degrees C. The main Bragg peak appears to split in two, indicating formation of a different structure at elevated temperatures. These findings are used to improve the PGM water phase diagram.
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| 2. |
- Falk, Yana Znamenskaya, et al.
(författare)
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Interactions of Perfluorohexyloctane With Polyethylene and Polypropylene Pharmaceutical Packaging Materials.
- 2020
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier. - 0022-3549 .- 1520-6017. ; 109:7, s. 2180-2188
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Tidskriftsartikel (refereegranskat)abstract
- Semifluorinated alkanes (SFAs) are aprotic solvents, which may be used as drug solvents for topical ocular applications, for instance, in dry eye syndrome. Their physical properties suggest that they might be prone to interaction with plastic materials, such as, polyethylene (PE) and polypropylene (PP), which are commonly used as packaging materials for pharmaceutical products. In this study, we investigate interactions of PE and PP with a liquid SFA perfluorohexyloctane (PFHO) using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross-polarized light microscopy. Binary phase diagrams of PFHO-PE and PFHO-PP systems demonstrating interactions of PFHO with the polymeric materials were constructed based on DSC data. According to this data, PFHO tends to lower the melting temperatures of PE and PP. The equilibrium values of solubilities of the polymers in PFHO and PFHO in the polymers were obtained by extrapolation of melting enthalpy data. Absorption of PFHO by PE and PP materials at ambient conditions after four weeks of equilibration was also studied by TGA. From the presented results, it may be concluded that thorough studies of interactions of PE or PP with SFAs are required when these materials are used as packaging components in SFA-based formulations.
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| 3. |
- Falk, Yana Znamenskaya, et al.
(författare)
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Langmuir - Blodgett monolayers of SBA-15 particles with different morphologies
- 2018
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 256, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- This study presents an optimized protocol for the deposition of mesoporous SBA-15 particles with platelet-like and rod-like morphologies on different types of supporting substrates using LangmuirBlodgett methodology, resulting in the formation of monolayers with porosity orientation controlled by the type, i. e. the morphology, of particles used over large areas. The morphology of the SBA-15 particles and specifically their aspect ratio are essential for the orientation of the particles and, hence, the orientation of the intrinsic porosity. Deposition on a surface, establishes a layer of SBA-15 platelets with pores oriented perpendicular to the substrate, or a layer of SBA-15 rods with pores oriented parallel to the substrate. In both cases, the oriented SBA-15 particles can be deposited onto areas that are larger than square centimeter using Langmuir-Blodgett technique. SEM characterization demonstrates formation of uniform close-packed layer of oriented mesoporous SBA-15 silica particles. Additionally, the particles coverage of the surface is independent and unaffected by the type of supporting substrate, which allows convenient experimental performance without requiring surface or particle modifications. In conclusion, Langmuir Blodgett is a convenient technique for deposition of mesoporous SBA-15 particles with different morphology types in order to obtain a close-packed layer. The methodology is suitable to create large area sensors, used in; for instance, bio-sensing applications. (C) 2017 Elsevier Inc. All rights reserved.
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| 4. |
- Gonzalez-Martinez, Juan Francisco, et al.
(författare)
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Humidity-induced phase transitions of surfactants embedded in latex coatings can drastically alter their water barrier and mechanical properties
- 2018
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Latex coatings are environmentally friendly i.e., they are formed from aqueous polymer dispersions, are cheap to produce and provide exceptional mechanical properties. Therefore, they are ubiquitous and can be found in a wide range of different applications such as paints and varnishes, pressure-sensitive adhesives, textiles, construction materials, paper coatings and inks. However, they also have weaknesses and their surfactant content is among them. Surfactants are often needed to stabilize polymer particles in the aqueous latex dispersions. These surfactants also form part of the coatings formed from these dispersions, and it is well-known that they can lower their performance. This work further explores this aspect and focuses on the role that embedded surfactant domains play in the response of latex coatings to humid environments. For this purpose, we made use of several experimental techniques where humidity control was implemented: quartz crystal microbalance with dissipation, atomic force microscopy and differential scanning calorimetry. By means of this multimethodological approach, we report that surfactants embedded in latex coatings can undergo humidity-induced transitions towards more hydrated and softer phases, and that this results in a drastic decrease of the mechanical and water barrier properties of the whole coatings. Subsequently, this work highlights the potential of taking into account the phase behavior of surfactants when choosing which ones to use in the synthesis of latex dispersions as this would help in predicting their performance under different environmental conditions.
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