| 1. |
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| 2. |
- Kjellman, Tomas, et al.
(författare)
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Influence of microporosity in SBA-15 on the release properties of anticancer drug dasatinib
- 2014
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry (RSC). - 2050-750X .- 2050-7518. ; 2:32, s. 5265-5271
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Tidskriftsartikel (refereegranskat)abstract
- The release of the hydrophobic cancer drug dasatinib from two mesoporous silica materials as drug delivery vehicles has been studied. One material is a reference 2D-hexagonal SBA-15 with the typical bimodal pore system with ordered primary mesopores and disordered intrawatI pores. The other material is a modified version of the same material where the intrawall porosity in the micropore regime has been selectively removed. Material characterization shows that, with the exception of the difference in intrawall porosity, the materials have identical properties. The drug dasatinib, a tyrosine kinase inhibitor, has been loaded, to the same extent, into the pores of both materials. The two materials give rise to very different release profiles of the drug. The presence of micropores leads to desired release properties: a high initial release of the drug, which is maintained over time. The lack of micropores also leads to a high initial release but followed by a rapid drop in the concentration of released drug, a consequence of its low solubility and hence crystallisation. We suggest that the presence of micropores in the carrier material, and the resultant kinetic release profile, leads to a stabilization of dasatinib in solution and to a sustained supersaturated level of the released drug. Our findings suggest that by controlling the mesoporous host with small variation in the textural properties, the kinetic release and crystallization behaviour of a drug can be altered. It is thus potentially possible to influence the drug post-release and thereby its bioavailability.
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| 3. |
- Andersson, Martin, 1974, et al.
(författare)
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Vesicle and bilayer formation of diphytanoylphosphatidylcholine (DPhPC) and diphytanoylphosphatidylethanolamine (DPhPE) mixtures and their bilayers' electrical stability
- 2011
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Ingår i: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82:2, s. 550-561
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Tidskriftsartikel (refereegranskat)abstract
- Lipid bilayers are of interest in applications where a cell membrane mimicking environment is desired. The performance of the lipid bilayer is largely dependent on the physical and chemical properties of the component lipids. Lipid bilayers consisting of phytanoyl lipids have proven to be appropriate choices since they exhibit high mechanical and chemical stability. In addition, such bilayers have high electrical resistances. Two different phytanoyl lipids, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1,2-diphytanoyl-sn-glycero-3-phosphoethanolamine(DPhPE), and various combinations of the two have been investigated with respect to their behavior in aqueous solutions, their interactions with solid surfaces, and their electrical stability. Dynamic light scattering, nuclear magnetic resonance diffusion, and cryogenic transmission electron microscopy measurements showed that pure DPhPC as well as mixtures of DPhPC and DPhPE consisting of greater than 50% (mol%) DPhPC formed unilamellar vesicles. If the total lipid concentration was greater than 0.15 g/l, then the vesicles formed solid-supported bilayers on plasma-treated gold and silica surfaces by the process of spontaneous vesicle adsorption and rupture, as determined by quartz crystal microbalance with dissipation monitoring and atomic force microscopy. The solid-supported bilayers exhibited a high degree of viscoelasticity, probably an effect of relatively high amounts of imbibed water or incomplete vesicle fusion. Lipid compositions consisting of greater than 50% DPhPE formed small flower-like vesicular structures along with discrete liquid crystalline structures, as evidenced by cryogenic transmission electron microscopy. Furthermore, electrophysiology measurements were performed on bilayers using the tip-dip methodology and the bilayers' capacity to retain its electrical resistance towards an applied potential across the bilayer was evaluated as a function of lipid composition. It was shown that the lipid ratio significantly affected the bilayer's electrical stability, with pure DPhPE having the highest stability followed by 3DPhPC:7DPhPE and 7DPhPC:3DPhPE in decreasing order. The bilayer consisting of 5DPhPC:5DPhPE had the lowest stability towards the applied electrical potential.
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| 4. |
- Han, Lu, et al.
(författare)
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Silica-Based Nanoporous Materials
- 2014
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Ingår i: Zeitschrift für Anorganische und Allgemeines Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 640:3-4, s. 521-536
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Forskningsöversikt (refereegranskat)abstract
- Ordered nanoporous structures are among the most fascinating and industrially important materials currently in use. The archetypal zeolite material has now been joined by an eclectic array of new structures that exhibit porosity over a wide range of length scales and with order/disorder expressed in a multitude of ways. This raises the bar in terms of characterization and extends a real challenge to the scientific community to fully understand the properties and potential future applications of such materials. In this review we discuss the importance of modern microscopy tools combined with diffraction in this endeavour and show how the details of even the most complex quasi-crystalline nanoporous architectures can be elucidated. We show by using the appropriate spherical aberration (C-s) corrections in scanning transmission electron microscopy it is possible to decipher all the individual silicon and aluminum atoms in a zeolite structure. Automated routines for using large electron diffraction datasets for crystal structure determination of nanocrystals is described making the need for large single crystal synthesis less-and-less important. The power of complementary combinations of surface tools such as atomic force microscopy and high-resolution scanning electron microscopy is discussed to elucidate crystal growth mechanisms. For mesoporous materials synthesized from self-organized organic mesophases electron microscopy reveals the details of the complex hierarchy of porosity so crucial for the functional performance of the structure.
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| 5. |
- Ruan, Juanfang, et al.
(författare)
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Transient Colloidal Stability Controls the Particle Formation of SBA-15
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:31, s. 11567-11574
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Tidskriftsartikel (refereegranskat)abstract
- A hypothesis about (transient) colloidal stability as a controlling mechanism for particle formation in SBA-15 is presented. The hypothesis is based on results from both in situ and ex situ investigations, including cryogenic transmission electron microscopy (cryo-TEM), UV-vis spectroscopy, and dynamic light scattering (DLS). Cryo-TEM images show that particles grow via the formation of silica-Pluronic-water flocs, which coalesce in a seemingly arbitrary manner. Despite this, the final material consists of well-defined particles with a small size distribution. We argue that the interface between the flocs and surrounding media is covered by Pluronic molecules, which provide steric stabilization. As the flocs grow, the coverage of polymers at the interface is increased until a stable size is reached, and that regulates the particle size. By targeting the characteristics of the Pluronic molecules, during the on-going synthesis, the hypothesis is tested. The results are consistent with the concept of (transient) colloidal stability.
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| 6. |
- Suga, Mitsuo, et al.
(författare)
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Recent progress in scanning electron microscopy for the characterization of fine structural details of nano materials
- 2014
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Ingår i: Progress in Solid State Chemistry. - : Elsevier BV. - 0079-6786 .- 1873-1643. ; 42:1-2, s. 1-21
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Forskningsöversikt (refereegranskat)abstract
- Research concerning nano-materials (metal-organic frameworks (MOFs), zeolites, mesoporous silicas, etc.) and the nano-scale, including potential barriers for the particulates to diffusion to/from is of increasing importance to the understanding of the catalytic utility. of porous materials when combined with any potential super structures (such as hierarchically porous materials). However, it is difficult to characterize the structure of for example MOFs via X-ray powder diffraction because of the serious overlapping of reflections caused by their large unit cells, and it is also difficult to directly observe the opening of surface pores using ordinary methods. Electron-microscopic methods including high-resolution scanning electron microscopy (HRSEM) have therefore become imperative for the above challenges. Here, we present the theory and practical application of recent advances such as through-the-lens detection systems, which permit a reduced landing energy and the selection of high-resolution, topographically specific emitted electrons, even from electrically insulating nano-materials.
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| 7. |
- Schmitt, Julien, et al.
(författare)
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Outset of the Morphology of Nanostructured Silica Particles during Nucleation Followed by Ultrasmall-Angle X-ray Scattering
- 2016
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:20, s. 5162-5172
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Tidskriftsartikel (refereegranskat)abstract
- Nucleation and growth of SBA-15 silica nanostructured particles with well-defined morphologies has been followed with time by small-angle X-ray scattering (SAXS) and ultrasmall-angle X-ray scattering (USAXS), using synchrotron radiation. Three different morphologies have been compared: platelets, toroids, and rods. SEM observations of the particles confirm that two key physical parameters control the morphology: the temperature and the stirring of the solution. USAXS curves demonstrate that primary particles with a defined shape are present very early in the reaction mixture, immediately after a very fast nucleation step. This nucleation step is detected at 10 min (56 degrees C) or 15 min (50 degrees C) after the addition of the silica precursor. The main finding is that the USAXS signal is different for each type of morphology, and we demonstrate that the difference is related to the shape of the particles, showing characteristic form factors for the different morphologies (platelet, toroid, and rod). Moreover, the size of the mesocrystal domains is correlated directly with the particle dimensions and shape. When stirred, aggregation between primary particles is detected even after 12 min (56 degrees C). The platelet morphology is promoted by constant stirring of the solution, through an oriented aggregation step between primary particles. In contrast, toroids and rods are only stabilized under static conditions. However, for toroids, aggregation is detected almost immediately after nucleation.
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| 8. |
- Agzenai, Y, et al.
(författare)
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In Situ X-ray Polymerization: From Swollen Lamellae to Polymer-Surfactant Complexes
- 2014
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 118:4, s. 1159-1167
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the monomer diallyldimethylammonium chloride (D) on the lamellar liquid crystal formed by the anionic surfactant aerosol OT (AOT) and water is investigated, determining the lamellar spacings by SAXS and the quadrupolar splittings by deuterium NMR, as a function of the D or AOT concentrations. The cationic monomer D induces a destabilization of the AOT lamellar structure such that, at a critical concentration higher than 5 wt %, macroscopic phase separation takes place. When the monomer, which is dissolved in the AOT lamellae, is polymerized in situ by X-ray initiation, a new collapsed lamellar phase appears, corresponding to the complexation of the surfactant with the resulting polymer. A theoretical model is employed to analyze the variation of the interactions between the AOT bilayers and the stability of the lamellar structure.
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| 9. |
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| 10. |
- Akesson, Anna, et al.
(författare)
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The effect of PAMAM G6 dendrimers on the structure of lipid vesicles
- 2010
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:38, s. 12267-12272
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Tidskriftsartikel (refereegranskat)abstract
- Dendrimers are polymers with unique properties that make them promising in a variety of applications such as potential drug and gene delivery systems. PAMAM dendrimers, in particular, have been widely investigated and are efficiently translocated into the cell. The mechanism of translocation, however, is still unknown. Recently it was proposed that PAMAM dendrimers are able to open holes in lipid bilayers by stealing lipid from the bilayer and forming "dendrisomes''. The present work intends to contribute in the clarification of this question: why are dendrimers able to translocate into the cell? We create simple models for cell membranes by using small lipid vesicles that present a single lipid phase at physiologically relevant conditions. We then follow the effect that dendrimers have on the structure of the vesicles by using a combination of various techniques: dynamic light scattering, cryo-TEM and small angle X-ray scattering. We discuss our results with respect to the previous findings and reflect on their possible implications for real translocation in living cells.
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