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1.
Donnan equilibrium and osmotic pressure in hollow polyelectrolyte microcapsules
David Haložan, Gleb B. Sukhorukov, Milan Brumen, Edwin Donath, Helmuth Möhwald, 2007, original scientific article

Abstract: A simple theoretical model of the Donnan equilibrium is applied to studies of distributions of ions between the external and internal volumes of hollow polyelectrolyte capsules as well as of concomitant osmotic pressure load on a capsule wall resulting from these distributions and the presence of polyanion. The model system consist of dispersed polyelectrolyte capsules in an electrolyte solution whereby two cases are considered with respect to the presence of the polyanion, either in the inner or external solution. It is assumed that the capsule wall is impermeable to polyanion, but water and all ions can freely penetrate. The model predictions are summarized by presenting the difference between the external pH, the pH of the inner solution and the osmotic pressure difference across the capsule wall, both in the dependence of sodium chloride concentration.
Keywords: biophysics, polyelectrolytes, polyelectrolyte capsules, Donnan equilibrium, osmotic pressure
Published in DKUM: 07.06.2012; Views: 2124; Downloads: 122
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2.
Flow cytometry of HEK 293T cells interacting with polyelectrolyte multilayer capsules containing fluorescein-labeled poly(acrylic acid) as a pH sensor
Uta Reibetanz, David Haložan, Milan Brumen, Edwin Donath, 2007, original scientific article

Abstract: Polyelectrolyte multilayer sensor capsules, 5 m in diameter, which contained fluorescein-labeled poly(acrylic acid) (PAAAF) as pH-sensitive reporter molecules, were fabricated and employed to explore their endocytotic uptake into HEK 293T cells by flow cytometry. The percentage of capsules residing in the endolysosomal compartment was estimated from the fluorescence intensity decrease caused by acidification. Capsules attached to the extracellular surface of the plasma membrane were identified by trypan blue quenching. The number of capsules in the cytoplasm was rather small, being below the detection limit of the method. The advantages of polyelectrolyte multilayer capsules are that the fluorophore is protected from interaction with cellular compartments and that the multilayer can be equipped with additional functions.
Keywords: biophysics, polyelectrolytes, multilayer capsules, polyelectrolyte capsules
Published in DKUM: 07.06.2012; Views: 1636; Downloads: 114
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3.
Lipid layers on polyelectrolyte multilayer supports
Martin Fischlechner, Markus Zaulig, Stefan Meyer, Irina Estrela-Lopis, Luis Cuéllar, Joseba Irigoyen, Paula Pescador, Milan Brumen, Paul Messner, Sergio Moya, Edwin Donath, 2008, original scientific article

Abstract: The mechanism of formation of supported lipid layers from phosphatidylcholine and phosphatidylserine vesicles in solution on polyelectrolyte multilayers was studied by a variety of experimental techniques. The interaction of zwitterionic and acidic lipid vesicles, as well as their mixtures, with polyelectrolyte supports was followed in real time by micro-gravimetry. The fabricated lipid-polyelectrolyte composite structures on top of multilayer coated colloidal particles were characterized by flow cytometry and imaging techniques. Lipid diffusion over the macroscopic scale was quantified by fluorescence recovery after photobleaching, and the diffusion was related to layer connectivity. The phospholipid-polyelectrolyte binding mechanism was investigated by infrared spectroscopy. A strong interaction of polyelectrolyte primary amino groups with phosphate and carboxyl groups of the phospholipids, leading to dehydration, was observed. Long-range electrostatic attraction was proven to be essential for vesicle spreading and rupture. Fusion of lipid patches into a homogeneous bilayer required lateral mobility of the lipids on the polyelectrolyte support. The binding of amino groups to the phosphate group of the zwitterionic lipids was too weak to induce vesicle spreading, but sufficient for strong adsorption. Only the mixture of phosphatidylcholine and phosphatidylserine resulted in the spontaneous formation of bilayers on polyelectrolyte multilayers. The adsorption of phospholipids onto multilayers displaying quarternary ammonium polymers produced a novel 3D lipid polyelectrolyte structure on colloidal particles.
Keywords: biophysics, lipids, lipid layers, electrolytes, multilayer supports
Published in DKUM: 07.06.2012; Views: 1806; Downloads: 73
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