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Biomedical subjects

Edwin Donath

Publications and source records attributed to Edwin Donath.

15 recordsLinked to original sources
PubMed2006

Virus-coated layer-by-layer colloids as a multiplex suspension array for the detection and quantification of virus-specific antibodies.

BACKGROUND: Suspension array technology has surpassed ELISA for automated, simultaneous detection and quantification of soluble biomarkers such as virus-specific antibodies. We describe assays in which antigens are attached to a lipid bilayer surrounding color-coded particles. METHODS: We used layer-by-layer technology to establish a multiplex suspension array with distinguishable microbeads coated with authentic viral surfaces to catch and quantify virus-specific antibodies in a flow cytometric analysis. Antigenic surfaces were generated by chimeric and wild-type baculoviruses plus 2 different influenza A virus subtypes fused to a lipid bilayer surrounding distinctly colored particles. Specificity of binding of chosen antibodies and sera was detected by immunofluorescence. Results of multiplex analysis were compared with results of ELISA. RESULTS: Titrations of virus-specific antibodies in the multiplex suspension array demonstrated specific binding to the viral surface proteins. The multiplex suspension array gave positive results for up to log 5-diluted primary antibodies with an approximately 5- to 10-fold reduced dynamic range compared with the respective ELISA. CONCLUSIONS: The bead-based multiplex suspension array is customizable and easy to establish. By displaying native influenza A virus surfaces and recombinant HIV-1 epitopes, the new assay provides a tool for the detection of major viral infections in humans.

Antibodies, Viral↗
PubMed2006

Defoliation and plasmid delivery with layer-by-layer coated colloids.

The uptake of polyelectrolyte multilayer coated colloids into cells, subsequent defoliation and plasmid delivery was studied by means of confocal microscopy and flow cytometry. Silica particles coated layer-wise with protamine and dextran sulfate were given to HEK 293T cells. Optimum uptake was found with protamine as the top layer. The particle uptake likely follows an non-receptor-mediated endocytotic pathway. Defoliation of polyelectrolyte multilayer coated particles within cells was demonstrated by the release of incorporated plasmids as indicated by the expression of plasmid encoded proteins using the enhanced green fluorescence proteine (pEGFP-C1) plasmid and a red fluorescence protein (pDsRed1-N1) plasmid. This proves, together with the direct observation of fluorescent layer debris, the defoliation of coated particles and the release of layer components into the cytoplasm. Particle uptake and GFP expression.

Animals↗
PubMed2005

Elasticity and adhesion of resting and lipopolysaccharide-stimulated macrophages.

Colloidal Force Microscopy was employed to study the viscoelastic and adhesive properties of macrophages upon stimulation with lipopolysaccharide (LPS). Force vs. distance measurements were performed. The adhesion of LPS-stimulated cells (separation force=37+/-3 nN) was almost twice as high as that of resting macrophages (16+/-1 nN). Upon retraction pulling of membrane tethers was observed. Tether lengths and forces at which rupture take place did not depend on stimulation. The reduced Young's modulus K, a measure of cytoskeleton elasticity, was three times lower than that of the control. The data show that LPS has profound effects on cytomechanical and adhesion properties of macrophages.

Cell Adhesion↗
PubMed2005

Interaction forces between cellulose microspheres and ultrathin cellulose films monitored by colloidal probe microscopy-effect of wet strength agents.

Colloidal probe microscopy was employed to study forces between cellulose surfaces upon addition of a series of cationic copolymers in aqueous solution, as model compounds for wet strength agents. The content of quaternary ammonium groups and primary amines was systematically varied in the cationic polymers, to distinguish between the importance of electrostatical and H-bonding effects. Cellulose microspheres were glued at the apex of tipless microfabricated cantilevers and used as colloidal probes. Ultra thin cellulose films and cellulose fibres were employed as model surfaces. The cellulose films of a thickness of about 5 nm were spin-coated from cellulose solution onto silicon substrates. The root-mean-square-roughness (RMS) was 0.3-0.8 nm. The cationic model polymers were compared to Servamine, a polymer employed as standard wet strength resin in papermaking industries. Force versus separation measurements showed a detailed picture of adhesion and contact breaking. Relatively strong adhesion of the order of 0.3 mJ/m(2) was observed with Servamine within a range of approximately 10 nm. At larger distances weak bond breaking and elastic chain pulling were identified. When approaching the surface one to two small jump-in's possibly related to strong binding of Servamine and subsequent attraction could be found in the case of Servamine. In contrast, all the model copolymers showed only a weak adhesion of 8-30 micro/m(2), i.e., an order of magnitude less than that of Servamine and subsequent elastic rupture domains. The contour length, persistence length and characteristic rupture distances were calculated by means of applying the WLC model. Measurements against cellulose fibres obtained from the production process proved the relevance of the model systems.

Amines↗
PubMed2004

Novel formulations of vitamins and insulin by nanoengineering of polyelectrolyte multilayers around microcrystals.

Microcapsules loaded with vitamin K3 (VK3), biotin, or insulin were prepared by using a novel coating technology based on the layer-by-layer (LbL) deposition of oppositely charged polyelectrolytes onto microcrystal templates. This produced multilayered, polymeric shells of varying thickness around the crystalline cores. Dissolution of the core material (VK3 with ethanol, biotin with basic solution, and insulin with acidic solution), resulted in its release through the shells. Microelectrophoresis was employed to monitor the microcrystal coating process; confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) were used to verify multilayer coating and the formation of hollow polymer shells following removal of the microcrystal templates. The release rates of both VK3 and insulin decreased as the wall thickness (the number of polyelectrolyte layers deposited onto the microcrystal cores), increased. The release time could be varied by a factor of more than ten, depending on the number of polyelectrolyte layers applied. Following the addition of 70 mass % ethanol, the solubility of VK3 increased by as much as 170-fold, resulting in an increased rate of VK3 release. By selecting appropriate polymer materials for the shells, and by controlling the number of polyelectrolyte layers applied, shells of various thickness, stiffness, aqueous solubility, dispersibility, biocompatibility, and permeability can be constructed.

Insulin↗
PubMed2004

Permeability and conductivity of red blood cell templated polyelectrolyte capsules coated with supplementary layers.

The permeability of ions and small polar molecules through polyelectrolyte multilayer capsules templated on red blood cells was studied by means of confocal microscopy and electrorotation. Capsules were obtained by removing the cell after polyelectrolyte multilayer formation by means of NaOCl treatment. This procedure results in cross-linking of poly(allylamine hydrochloride) (PAH) molecules and destroying poly(styrene sulfonate) (PSS) within the multilayer. Capsules are obtained being remarkably different from layer-by-layer (LbL) capsules. These capsules are rather permeable for low as well as for high molecular weight species. However, upon adsorption of extra polyelectrolyte layers the permeability decreased remarkably. The assembly of six supplementary layers of PAH and PSS rendered the capsule almost impermeable for fluorescein. Resealing by supplementary layers is a potential means for filling and release control. By means of electrorotation measurements, it was shown that the capsule walls obtained isolating properties in electrolyte solutions. Conclusions are drawn concerning the mechanism of permeability through cell templated polyelectrolyte multilayer capsules.

Capsules↗
PubMed2003

Swelling and shrinking of polyelectrolyte microcapsules in response to changes in temperature and ionic strength.

Swelling and shrinking of polyelectrolyte microcapsules consisting of poly(styrene sulfonate, sodium salt) (PSS) and poly(diallyldimethyl ammonium) chloride (PDADMAC) multilayers have been observed in response to temperature and electrolyte exposure, respectively. Heat-induced capsule swelling and capsule wall volume reduction were observed by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). On the other hand, pronounced shrinking in diameter induced by exposure to an electrolyte was observed in parallel to increases in the thickness of the capsule wall. The estimated wall volume was reduced to two thirds of the control for the salt-exposed capsules and one half for the salt-exposed and simultaneously annealed capsules. This reduction in volume was supposedly mainly caused by the compression of the capsule wall due to the ionic screening from the electrolyte. The highly porous microstructure of the multilayers and loosely bound PSS/PDADMAC complex are thought to be responsible for the structure of the PSS/PDADMAC capsules being easily modulated upon annealing and salt-exposure.

Journal Article↗
PubMed2002

Hollow polymer shells from biological templates: fabrication and potential applications.

Three-dimensional ultrathin polymer shells have been produced by a combination of step-by-step adsorption of polyelectrolytes on glutaraldehyde-treated human erythrocytes and subsequent solubilization of the cytoplasmatic constituents by means of a deproteinizing agent. The obtained hollow films preserve both the size and shape of the templating cells. This opens a pathway for the fabrication of polymeric capsules within a wide range of size and shape by using various biological templates. They may have exciting potential applications, such as templates for nanocomposites, as containers for a large class of materials, or as cages for chemical reactions. The thickness of the films can be adjusted over a large range: from a few nm up to several tens of nm. The polymer shells are permeable to small molecules and ions but not to macromolecules. An increase in the ionic strength of the solution up to 100 mmol make the capsules permeable for proteins. Permeability and conductivity studies have provided evidence that the adsorption of lipids on polyelectrolyte layers is a means of producing capsules with controlled permeability properties. 6-Carboxyfluorescein and Rhodamin 6G were precipitated within the capsules.

Biotechnology↗
PubMed2002

Precipitation of inorganic salts inside hollow micrometer-sized polyelectrolyte shells.

Hollow polymer shells formed by layer-by-layer adsorption of oppositely charged polyelectrolytes onto micrometer-sized colloidal particles with subsequent decomposition of the colloidal core were employed as a model system for the study of inorganic crystallization reactions in restricted volumes. The size-selective permeability of shells is used for spatially controlling the precipitation of inorganic salts CaCO3 and BaCO3 into the shell interior. Outside the shells the precipitation was suppressed by the polymers, which are unable to penetrate the shell wall. The precipitates were studied by scanning electron microscopy and atomic force microscopy. The fundamental and applied aspects of research on spatially confined synthesis of inorganic particles are under discussion.

Journal Article↗
PubMed2002

Investigation of pseudoisocyanine aggregates formed on polystyrenesulfonate.

The interaction of 1,1'-diethyl-2,2'-cyanine (PIC), a non-fluorescent cationic dye known to form emissive J-aggregates in aqueous solutions, with the polyelectrolyte poly(styrenesulfonate) (PSS) is investigated by absorption and fluorescence spectroscopy. Depending on the amount of polyelectrolyte added, three regimes are identified. At a large excess of PIC, there is an equilibrium between the PIC monomer and a non-fluorescent PIC aggregate characterized by a strong absorption band centered at 565 nm. As the amount of PSS increases, we observe the growth of the PIC J-aggregate onto the PSS backbone, characterized by a sharp absorption band at 572 nm and a narrow emission at 577 nm. At a large excess of PSS, the major species consists of PIC molecules adsorbed independently along the polyelectrolyte chains.

Journal Article↗
PubMedDate not supplied

Polyelectrolyte complexes and layer-by-layer capsules from chitosan/chitosan sulfate.

Polyelectrolyte complex formation of chitosans of varying average molecular weight and degree of acetylation with chitosan sulfate or poly(styrene sulfonate) was studied by static light scattering in dilute solution at various ionic strengths. Unlike the molecular weight, the degree of acetylation was found to have a significant effect on the resultant structural densities of the complexes. The same system was applied to the preparation of micrometer-sized hollow shells by means of a layer-by-layer technique (in total eight layers). Their behavior toward fluorescent probes such as fluorescein and rhodamin 6G or fluorescein isothiocyanate labeled dextrans at various ionic strengths and pH (observed by confocal laser light scanning microscopy) could be understood through a discussion of electrostatic forces between the highly charged shells and the probes to be dominant. At an ionic strength of 0.1 M and above, charge effects are largely suppressed (screening effect) and a size-dependent "cutoff" for the permeation of the macromolecular fluorophore was observed.

Acetylation↗
PubMedDate not supplied

Protamine assembled in multilayers on colloidal particles can be exchanged and released.

Biocomposite thin films assembled on colloidal particles by means of layer-by-layer adsorption have been suggested as drug carriers and diagnostic devices. Protamine (PRM)/dextransulfate (DXS) and protamine/bovine serum albumine (BSA) multilayers were fabricated on colloidal silica and subsequently investigated by means of fluorescence activated cell sorting (FACS) and microelectrophoresis. Fluorescein labeled polyelectrolytes were embedded at different positions in the multilayers as a marker for layer growth. FACS showed that PRM and DXS formed regular growing stable multilayers, yet adsorbed PRM can be nevertheless exchanged with PRM in solution during layer formation and also after the multilayer formation has been completed. Up to 90% of the PRM pool was available for exchange. PRM together with BSA as demonstrated by SFM did not form multilayers under the applied conditions although the zeta-potential, commonly used as an indicator for stepwise adsorption, observed characteristic alternations. The capability of bound PRM to exchange with PRM in solution is attributed to its relatively small size. The demonstrated exchange may have importance in designing multilayers with smart release features. Furthermore, FACS proved to be a rather suitable means to quantify the aggregation behavior during coating and washing. Singulets, doublets, triplets, and aggregates of higher order could be clearly resolved. The aggregation of particles coated with PRM/DXS layers was higher than that of silica particles coated with PAH/PSS layers. In the first case about 50% of all recorded events are attributed to aggregats, while the PAH/PSS coating produced only about 10% aggregates.

Adsorption↗