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| 2. |
- Dédinaité, Andra, et al.
(författare)
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Interfacial properties of chitosan-PEO graft oligomers: Surface competition with unmodified chitosan oligomers
- 2006
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Ingår i: Progress in Colloid and Polymer Science. - Berlin/Heidelberg : Springer-Verlag. - 0340-255X .- 1437-8027. ; 132, s. 124-130
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Tidskriftsartikel (refereegranskat)abstract
- Oligomers of chitosan carrying 45 units long poly(ethylene oxide), PEO, chains grafted to the C-6 position of the sugar units were prepared using a novel synthesis route. The graft density was high, close to one poly(ethylene oxide) chain grafted to each sugar unit of the chitosan oligomer but a small fraction of unreacted chitosan remained in the sample. The molecular weight distribution of the sample was determined using GPC. The interfacial properties of the chitosan-PEO graft oligomers were evaluated using X-ray photoelectron spectroscopy and surface force measurements. It was found that the small fraction of unreacted chitosan was significantly enriched at the solid-solution interface on negatively charged muscovite mica surfaces. The interactions between chitosan-PEO oligomer coated surfaces were found to be dominated by the extended PEO chains, and at high coverage the measured forces were consistent with those expected for polymer brushes. Addition of salt up to 10 mM did not result in any significant desorption of preadsorbed oligomer layers.
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| 3. |
- Pettersson, Torbjörn, et al.
(författare)
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The Effect of Salt Concentration and Cation Valency on Interactions Between Mucin-Coated Hydrophobic Surfaces
- 2008
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Ingår i: Progress in Colloid and Polymer Science. - Berlin, Heidelberg : Springer. - 0340-255X .- 1437-8027. - 9783540680185 ; 134, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The AFM colloidal probe technique has been utilized in order to investigate the forces acting between preadsorbed mucin layers on uncharged, hydrophobic mercaptohexadecane-coated gold surfaces. Layers with some highly extended tails are formed when the adsorption proceeds from 25 ppm mucin solution in 30 mM NaNO3. The effects of salt concentration and cation valency on the interactions have been explored using NaCl, CaCl2, and LaCl3 in the concentration range 1–100 mM. It will be shown that the results in NaCl, where the tail length decreases as the salt concentration is increased, can be rationalized by considering the polyelectrolyte nature of mucin and the screening of intralayer electrostatic interactions between charged groups, mainly anionic sialic acid. When multivalent cations are present in solution a significant compaction of the mucin layer occurs even at low concentrations (1 mM), suggesting binding of these ions to the anionic sites of mucin. The results are discussed in relation to previous data from quartz crystal microbalance measurements on the same systems.
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| 5. |
- Balogh, Joakim, et al.
(författare)
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Investigating the Effect of Adding Drug (Lidocaine) to a Drug Delivery System Using Small-Angle X-Ray Scattering
- 2008
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Ingår i: Colloids for Nano- and Biotechnology (Progress in Colloid and Polymer Science). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0340-255X. - 9783540851332 ; 135, s. 101-106
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Konferensbidrag (refereegranskat)abstract
- The effect on a model drug delivery system when adding a drug, lidocaine, has been studied. Temperature and concentration dependence of a nonionic microemulsion with part of the oil, 1 and 10 vol. %, substituted with drug has been investigated. A nonionic oil-in-water microemulsion consisting of CH3(CH2)(11)(OCH2CH2)(5)OH, (C12E5), decane, water and the drug (lidocaine) that has been used to substitute part of the oil was studied. The microscopic differences have been derived from small-angle X-ray scattering (SAXS) data and the results are compared with light scattering data. Using these results together with the macroscopic differences, as observed in the phase diagram (lowering of phase boundaries), between the systems with and without lidocaine can be explained.
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| 6. |
- Costa, Fatima, et al.
(författare)
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Drug Release and Skin Permeation from Lipid Liquid Crystalline Phases
- 2008
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Ingår i: Colloids for Nano- and Biotechnology (Progress in Colloid and Polymer Science). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0340-255X. - 9783540851332 ; 135, s. 119-129
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Konferensbidrag (refereegranskat)abstract
- We have studied drug release and skin permeation from several different liquid crystalline lipid formulations that may be used to control the respective release rates. We have studied the release and permeation through human skin of a water-soluble and amphiphilic drug, propranolol hydrochloride, from several formulations prepared with monoolein and phytantriol as permeation enhancers and controlled release excipients. Diolein and cineol were added to selected formulations. We observed that viscosity decreases with drug load, wich is compatible with the occurrence of phase changes. Diolein stabilizes the bicontinuous cubic phases leading to an increase in viscosity and sustained release of the drug. The slowest release was found for the cubic phases with higher viscosity. Studies on skin permeation showed that these latter formulations also presented lower permeability than the less viscous monoolein lamellar phases. Formulations containing cineol originated higher permeability with higher enhancement ratios. Thus, the various formulations are adapted to different circumstances and delivery routes. While a slow release is usually desired for drug sustained delivery, the transdermal route may require a faster release. Lamellar phases, which are less viscous, are more adapted to transdermal applications. Thus, systems involving lamellar phases of monoolein and cineol are good candidates to be used as skin permeation enhancers for propranolol hydrochloride.
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| 7. |
- Gonzalez Perez, Alfredo, et al.
(författare)
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Temperature Induced DNA Compaction in a Nonionic Lamellar Phase
- 2008
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Ingår i: Colloids for Nano- and Biotechnology (Progress in Colloid and Polymer Science). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0340-255X. - 9783540851332 ; 135, s. 174-180
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Konferensbidrag (refereegranskat)abstract
- A nonionic lamellar phase was prepared using C10E3 in buffer solution at pH = 7.6. A suitable T4DNA concentration around 5 wt % was immobilized in a lamellar phase with 40 wt % C10E3. The mixed system was investigated at two temperatures, 25 and 5 degrees C by using cryo-fracture TEM direct imaging, fluorescence microscopy and small-angle X-ray scattering. The surprising results where obtained showing that the DNA conformation can be tuned to compacted and extended state at 25 and 5 degrees C, respectively. Additionally, DNA is aligned with a preferential orientation in the direction of the flow by simply injecting the sample in a capillary.
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