| 1. |
- Vandoolaeghe, Pauline, et al.
(author)
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Adsorption of cubic liquid crystalline nanoparticles on model membranes
- 2008
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In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 4:11, s. 2267-2277
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Journal article (peer-reviewed)abstract
- The interactions of lipid based cubic liquid crystalline nanoparticles (Cubosome (R)) with surface supported model membranes constituted of dioleylphosphatidylcholine ( DOPC) have been studied in situ by use of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectivity. The systems investigated were cubic phase dispersions of glycerol monooleate (GMO) stabilised by a non-ionic block copolymer, Pluronic (R) F-127. The interaction between the cubic nanoparticles and the lipid bilayer is a dynamic process where the nanoparticles initially adsorb at the bilayer surface. Interfacial lipid exchange takes place where GMO is delivered into the bilayer and DOPC is extracted into the nanoparticle (34% loss). A subsequent release of the adsorbates can be triggered when the solution concentration exceeds 0.002 mg ml(-1). The release shows that the attractive interaction between the cubic nanoparticles and lipid bilayer is unstable after sufficient exchange of material takes place.This instability is indicative of a local phase separation at the interface between the bilayer and the nanoparticles, which causes desorption of nanoparticles. Some particles remain attached to the bilayer even hours after the initial interaction. The ability to trigger the release of the nanoparticles through increasing the solution concentration offers exciting potential in the design of drug delivery aids.
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| 2. |
- Wacklin, Hanna, et al.
(author)
-
Distribution of reaction products in phospholipase A(2) hydrolysis
- 2007
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In: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736. ; 1768:5, s. 1036-1049
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Journal article (peer-reviewed)abstract
- We have monitored the composition of supported phospholipid bilayers during phospholipase A(2) hydrolysis using specular neutron reflection and ellipsometry. Porcine pancreatic PLA(2) shows along lag phase of several hours during which the enzyme binds to the bilayer surface, but only 5 +/- 3% of the lipids react before the onset of rapid hydrolysis. The amount of PLA(2), which resides in a 21 +/- 1 angstrom thick layer at the water-bilayer interface, as well as its depth of penetration into the membrane, increase during the lag phase, the length of which is also proportional to the enzyme concentration. Hydrolysis of a single-chain deuterium labelled d(31)-POPC reveals for the first time that there is a significant asymmetry in the distribution of the reaction products between the membrane and the aqueous environment. The lyso-lipid leaves the membrane while the number of PLA(2) Molecules bound to the interface increases with increasing fatty acid content. These results constitute the first direct measurement of the membrane structure and composition, including the location and amount of the enzyme during hydrolysis. These are discussed in terms of a model of fatty-acid mediated activation of PLA(2).
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