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PubMed1996

Light Scattering Study of Magnetic Latex Particles and Their Interaction with Polyelectrolytes.

Commercially available latex particles with superparamagnetic inclusions have been characterized by polarized and depolarized dynamic light scattering. The particles are spherical, but the larger ones (R(g) approximately 0.1 µm) with many magnetic inclusions behave in dynamic light scattering experiments like symmetric tops while the smaller particles do not. The as-received materials had a broad size distribution, but more narrowly distributed particles were prepared by selective filtration for use in probe diffusion and stability studies. The interaction of these negatively charged particles with a linear polyelectrolyte, negatively charged sodium polystyrene sulfonate, was studied by static and dynamic light scattering. Depolarized dynamic light scattering is particularly sensitive to changes in the stability of the colloids or interaction with the polyelectrolyte. The polyelectrolyte can prevent or reverse salt-induced aggregation of the superparamagnetic latex particles. Fluorescence photobleaching recovery experiments to monitor the mobility of fluorescently labeled polyelectrolyte suggest that it is not bound to the latex particles; apparently, a mechanism other than steric stabilization is involved. The dependence of the diffusion of the superparamagnetic latex particles upon added salt is discussed in terms of the ion atmosphere surrounding the polyelectrolyte.

Journal Article↗
PubMed1999

Adsorption Kinetics of Polyelectrolytes on Planar Surfaces under Flow Conditions.

The focus of our work has been to develop a theory of adsorption kinetics for polyelectrolytes in a flow cell onto planar surfaces in the framework of the two-dimensional model and to study adsorption processes of polyelectrolytes on a planar surface by ellipsometry. We have studied the adsorption kinetics of water-soluble cationic poly(vinylamine) hydrochloride homopolymer from aqueous solution onto both silicon wafers and polystyrene films by ellipsometry. Equations were derived to calculate (a) the equilibrium adsorption, (b) the thickness of the adsorbed layer, (c) the activation energy of adsorption for water-soluble polyelectrolytes, (d) the rate constant for the water-soluble polyelectrolytes, (e) the effective coefficients of diffusion in the adsorbed layer, and (f) the time needed to attain the equilibrium state for the adsorption of the water-soluble polyelectrolytes in a flow cell. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Adsorption of polyelectrolyte-nanoparticle systems on silica: influence of ionic strength.

In this work the effect of ionic strength on the adsorption behavior of cationic polyelectrolyte (acrylamide-acrylamidopropyltrimethylammonium chloride) and negatively charged silica particles has been studied by means of ellipsometry. The adsorption of the polyelectrolyte was observed to increase with increasing salt concentration, a behavior typical for polyelectrolytes with a screening-reduced solvency and a nonelectrostatic affinity for the surface. A similar dependence on the ionic strength was observed when studying the electrolyte effect on the nanoparticle adsorption to the preadsorbed polyelectrolyte film, suggesting that the polyelectrolyte surface conformations largely govern the binding capacity of the particles to the surface.

Journal Article↗
PubMed1985

Chemiluminescence and superoxide generation by leukocytes stimulated by polyelectrolyte-opsonized bacteria. Role of histones, polyarginine, polylysine, polyhistidine, cytochalasins, and inflammatory exudates as modulators of oxygen burst.

Human blood leukocytes generate intense luminol-dependent chemiluminescence (LDCL) following stimulation by streptococci and by Gram negative rods which had been preopsonized by cationic polyelectrolytes (histone, poly L-arginine-PARG, poly L-histidine-PHSTD). Streptococci but not Gram negative rods or hyaluronic acid-rich streptococci (group C) also induced intense LDCL following opsonization with the anionic polyelectrolytes-dextran sulfate or polyanethole sulfonate (liquoid) suggesting that the outer surfaces of different bacteria bound anionic polyelectrolytes to different extents. Both normal and immune serum, synovial fluids and pooled human saliva inhibited the LDCL responses induced by streptococci preopsonized with poly cations. On the other hand, bacteria which had been first preopsonized by the various body fluids and then subjected to a second opsonization by cationic ligands ("sandwiches"), induced a very intense LDCL response in leukocytes. Streptococci which had been preopsonized by PARG, histone or by PHSTD also triggered superoxide generation by blood leukocytes, which was markedly enhanced by a series of cytochalasins. PHSTD alone induced the formation of very large amounts of superoxide. Paradoxically, the same concentrations of cytochalasins B or C which markedly boosted the generation of superoxide following stimulation of leukocytes with soluble or particulate ligands, had a strong inhibitory effect on the generation of LDCL. On the other hand cycochalasins failed to inhibit LDCL which had been induced by phorbol myristate acetate (PMA). Peritoneal macrophages which had been harvested from C. parvum-stimulated mice, generated more LDCL and superoxide following stimulation by PARG than macrophages obtained from proteose peptone-stimulated mice. Macrophages which had been activated either by proteose peptone or by C. parvum and cultivated for 2 hours on teflon surfaces, generated much more LDCL than macrophages which had been cultivated for 24 hours on teflon surfaces. Both cationic and anionic polyelectrolytes mimic the effects of antibodies as activators of the oxygen burst in blood leukocytes and in macrophages. Such polyelectrolytes can serve as models to further study leukocyte-bacteria interactions in infectious and inflammatory sites.

Adult↗
PubMed1983

Grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber.

Using a [3H]-labelled polyelectrolyte as a tracer, the 60Co grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber was studied. The polyelectrolyte was labelled by the coupling of a radioactive amine to carboxylate groups of the polyelectrolyte. The amount of grafted polyelectrolyte was found to be dependent on the radiation dose.

Adsorption↗
PubMed1983

Hydrogels by irradiation of a synthetic heparinoid polyelectrolyte.

Gamma irradiation of aqueous solutions of a synthetic heparinoid polyelectrolyte results in the formation of hydrogels, varying in water content and mechanical strength. The equilibrium water content and the mechanical strength of the hydrogels are dependent on the initial polyelectrolyte concentration, the molecular weight of the polyelectrolyte, the percentage of double bonds in the polyelectrolyte and the radiation dose. The polyelectrolyte hydrogels do not deplete Antithrombin III from blood and there is no activation of factor XII according to an in vitro kallikrein generation test. However, in a very sensitive test for factor XII activation (contact promoted shortening of the thrombotest) a slight activation of this factor was observed.

Biocompatible Materials↗
PubMed2006

Human osteosarcoma cell adhesion behaviour on hydroxyapatite integrated chitosan-poly(acrylic acid) polyelectrolyte complex.

A novel degradable composite system has been prepared by integrating hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2), (HAP) in a polyelectrolyte complex matrix of chitosan (CHI) and poly(acrylic acid) (PAA). The composite was formulated by integrating 80 wt.% HAP in the polyelectrolyte complex matrix of CHI and PAA in the ratio 40/60 (designated as CPH). The composite could be easily fabricated into clinically significant shapes by a simple moulding procedure intended for bone graft applications. The adhesion behaviour of human osteosarcoma (HOS) cells on this degradable composite system was studied by selecting the polyelectrolyte complex, CHI/PAA 40/60 (designated as CP) as control sample. Light microscopic observations show that cells around CPH retained the typical morphology of HOS cells while cells around the polyelectrolyte complex showed a cytotoxic effect. The adhesion behaviour as well as morphological responses of the seeded cells was further investigated by scanning electron microscopy. The scanning electron micrographs of the polyelectrolyte complex, CP, showed the presence of rounded cells with raised nuclear regions, indicating delayed spreading; cells adhered on CPH were flattened with filopodia and showed good attachment and spreading, indicating better adhesion onto the HAP integrated composite. Comparing the MTT assay for quantitative evaluation of cell viability, CPH showed a higher percentage of metabolically active cells compared to CP.

Acrylic Resins↗
PubMed2004

The bridging force between two plates by polyelectrolyte chains.

The interaction between particles in a colloidal system can be significantly affected by their bridging by polyelectrolyte chains. In this paper, the bridging is investigated by using a self-consistent field approach which takes into account the van der Waals interactions between the segments of the polyelectrolyte molecules and the plates, as well as the electrostatic and volume exclusion interactions. A positive contribution to the force between two plates is generated by the van der Waals interactions between the segments and the plates. This positive (repulsive) contribution plays an important role in the force when the distances between the plates are small. With increasing van der Waals interaction strength between segments and plates, the force between the plates becomes more repulsive at small distances and more attractive at large distances. When the surfaces of the plates have a constant surface electrical potential and a charge sign opposite to that of the polyelectrolyte chains, the force between the two plates becomes less attractive as the bulk polyelectrolyte concentration increases. This behavior is due to a higher bulk counterion concentration dissociated from the polyelectrolyte molecules. At short distances, the force between plates is more repulsive for stiffer chains. A comparison between theoretical and experimental results regarding the contraction of the interlayer separation between the platelets of vermiculite clays against the concentration of poly(vinyl methyl ether) was made.

Journal Article↗
PubMed2004

Intrinsic charge and Donnan potentials of grafted polyelectrolyte layers determined by surface conductivity data.

In order to characterize grafted polyelectrolyte layers based on electrokinetic measurements a theory of the surface conductivity Ksigma was developed, starting from the model of thick polyelectrolyte layers with uniform segment distribution and dissociable groups with an unknown pK value. According to this model the inner part of the polyelectrolyte layer adjacent to the substrate is considered to be isopotential while the potential decay occurs in a zone near the solution side of the layer. A simple equation for the Donnan potential psiD as a function of pH, pK, electrolyte concentration C0, and volume charge density rho was obtained. In the derived equation Ksigma is directly related to psiD while the other terms have less influence on the magnitude of Ksigma and can be accounted for in a second approximation using psiD as determined from the measured Ksigma. Evaluation of the suggested model indicates that Ksigma measurements provide an effective method to characterize polyelectrolyte layers by analyzing the dependence of psiD on pH and C0: The magnitude of Ksigma yields information about the surface charge at complete dissociation of the ionizable groups. The dependence of Ksigma on pH and C0 can be used for the determination of the pK value of the dissociating functions and the segment volume fraction of the polyelectrolyte can be estimated using the measured value of rho.

Journal Article↗
PubMed2004

Fluorescence and ESR studies of the conformational behavior of oppositely charged polyelectrolytes at solid/liquid interfaces.

The conformational behavior of oppositely charged polyelectrolytes on alumina in solutions was investigated by means of excimer fluorescence and electron spin resonance spectroscopy using maleic acid-propene copolymer labeled with pyrene or TEMPO. It was found that the ability of the polyanion at the surface for conformational rearrangements is strongly influenced by the constraints of the adsorbed state that restrict its complexation. Polyelectrolyte complexes (PEC) formed by mixing of the oppositely charged polyelectrolytes exhibited extreme coiling due to the screening of the charged groups. The polyelectrolytes undergo spreading during the adsorption process due to the electrostatic attraction. Surface binding can irreversibly limit the flexibility for the reconformation process to a great extent. It is also shown here that a flatter adsorbed state could be reached by sequential adsorption of polyanion and polycation than could be reached by the direct adsorption of the polyelectrolyte complex itself.

Journal Article↗
PubMed2005

Surface viscoelastic properties of floating polyelectrolyte multilayers films: a capillary wave study.

A capillary wave technique was used to study the viscoelastic properties of floating polyelectrolyte multilayers of (PSS/PAH)(n) at the air-water interface. Oppositely charged polyelectrolyte layers were adsorbed onto two different Langmuir monolayers, either the lipid dimethyldioctadecylammonium bromide (DODAB) or the block copolymer poly(styrene-b-sodium acrylate) (PS-b-PAA). The results allow to propose a schematic representation of the multilayers in three zones: Zone I as a precursor, representing the adhesion between the Langmuir monolayer and the bulk polyelectrolyte multilayer. Zone II forms a bulk or core zone of the multilayer. Zone III as an outer zone in direct contact with the aqueous phase. The results show an increase of the elasticity after the formation of four polyelectrolyte layers accompanied by an apparent negative viscosity. This behaviour was interpreted as a translation of elasticity dominance from zone I to zone II. The Young modulus of seven layers was in the same order of magnitude as observed for planar polyelectrolyte multilayer films.

Journal Article↗
PubMed2006

Nature and significance of the interactions between amyloid fibrils and biological polyelectrolytes.

Charged polyelectrolytes such as glycosaminoglycans and nucleic acids have frequently been found associated with the proteinaceous deposits in the tissues of patients with amyloid diseases. We have investigated the nature and generality of this phenomenon by studying the ability of different polyanions, including DNA, ATP, heparin, and heparan sulfate, to promote the aggregation of amyloidogenic proteins and to bind to the resulting aggregates. Preformed amyloid fibrils of human muscle acylphosphatase and human lysozyme, proteins with a net positive charge at physiological pH values, were found to bind tightly to the negatively charged DNA or ATP. The effects of the polyelectrolytes on the kinetics of aggregation were studied for acylphosphatase, and the presence of ATP, DNA, or heparin was found to increase its aggregation rate dramatically, with a degree dependent on the net charge and size of the polyanion. Magnesium or calcium ions were found to attenuate, and ultimately to suppress, these interactions, suggesting that they are electrostatic in nature. Moreover, heparin was found to stabilize the aggregated state of acylphosphatase through compensation of electrostatic repulsion. Noteworthy, differences in affinity between native and aggregated acylphosphatase with heparin suggest that amyloid fibrils can themselves behave as polyelectrolytes, interacting very strongly with other polyelectrolytes bearing the opposite charge. Within an in vivo context, the strengthening of the electrostatic interactions with other biological polyelectrolytes, as a consequence of protein misfolding and aggregation, could therefore result in depletion of essential molecular components and contribute to the known cytotoxicity of amyloid fibrils and their precursors.

Amyloid↗
PubMed2000

Polyelectrolyte molecular weight and electrostatically-induced domains in lipid bilayer membranes.

Polyelectrolyte-induced domain formation in charged lipid bilayer membranes was investigated as a function of polyelectrolyte molecular weight using 2H nuclear magnetic resonance (NMR) spectroscopy. Lipid bilayers consisting of mixtures of alpha- or beta-choline-deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC-alpha-d2 or POPC-beta-d2) plus the cationic amphiphile 1,2-dioleoyl-3-(dimethylamino)propane (DODAP) were exposed to the anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSSS) of various molecular weights. Regardless of molecular weight, PSSS produced dual component 2H NMR spectra, indicating two distinct POPC populations, corresponding to PSSS-bound and PSSS-free lipid, in slow exchange with one another. Analysis of the 2H NMR subspectra quadrupolar splittings and intensities showed the PSSS-bound domain to be enriched in DODAP, with the PSSS-free domain correspondingly depleted. At polyelectrolyte loadings below global charge equivalence, PSSS bound DODAP stoichiometrically for all PSSS molecular weights, indicating that the polyelectrolyte chain lies flat upon the membrane surface. At higher PSSS loadings the domains dissipated, leading to single component 2H NMR spectra. At high NaCl concentrations PSSS dissociated from the bilayer surface. Domain size on a per PSSS chain basis increased while the degree of enrichment with DODAP decreased progressively as the PSSS chain length decreased. Such molecular weight-dependent domain characteristics have not been predicted theoretically and need to be taken into account in future refinements of domain models.

Electrochemistry↗
PubMedDate not supplied

Vascular smooth muscle cells on polyelectrolyte multilayers: hydrophobicity-directed adhesion and growth.

Polyelectrolyte multilayer films were employed to support attachment of cultured rat aortic smooth muscle A7r5 cells. Like smooth muscle cells in vivo, cultured A7r5 cells are capable of converting between a nonmotile "contractile" phenotype and a motile "synthetic" phenotype. Polyelectrolyte films were designed to examine the effect of surface charge and hydrophobicity on cell adhesion, morphology, and motility. The hydrophobic nature and surface charge of different polyelectrolyte films significantly affected A7r5 cell attachment and spreading. In general, hydrophobic polyelectrolyte film surfaces, regardless of formal charge, were found to be more cytophilic than hydrophilic surfaces. On the most hydrophobic surfaces, the A7r5 cells adhered, spread, and exhibited little indication of motility, whereas on the most hydrophilic surfaces, the cells adhered poorly if at all and when present on the surface displayed characteristics of being highly motile. The two surfaces that minimized cell adhesion consisted of two varieties of a diblock copolymer containing hydrophilic poly(ethylene oxide) and a copolymer bearing a zwitterionic group AEDAPS, (3-[2-(acrylamido)-ethyldimethyl ammonio] propane sulfonate). Increasing the proportion of AEDAPS in the copolymer decreased the adhesion of cells to the surface. Cells presented with micropatterns of cytophilic and cytophobic surfaces generated by polymer-on-polymer stamping displayed a surface-dependent cytoskeletal organization and a dramatic preference for adhesion to, and spreading on, the cytophilic surface, demonstrating the utility of polyelectrolyte films in manipulating smooth muscle cell adhesion and behavior.

Animals↗
PubMed2001

Polyelectrolyte multilayers prepared from water-soluble poly(alkoxythiophene) derivatives.

Electronically conducting polyanion and polycation based on poly(alkoxythiophene) derivatives, poly-3-(3'-thienyloxy)propanesulfonate (P3TOPS) and poly-3-(3'-thienyloxy)propyltriethylammonium (P3TOPA) have been synthesized. Both polymers are water-soluble and exhibit high conjugation length in solution and in the solid state. These polyelectrolytes were used to prepare conducting and electroactive polyelectrolyte multilayers by the sequential layer-by-layer adsorption technique. In aqueous solutions multilayers of P3TOPS with inactive polyelectrolytes (e.g., poly(diallyldimethylammonium chloride), PDADMA) displayed electrochemical and optical behavior similar to polythiophene films prepared in organic media. Their in-plane conductivity was low (ca. 1.6 x 10(-)(5) S cm(-)(1)). The conductivity could, however, be increased by a factor of ca. 40 in "all-thiophene" films, in which P3TOPA was substituted for the inactive polycation (PDADMA). The interpenetration of layers is of prime importance in films containing conducting components. The interpenetration of P3TOPS was studied by measuring the charge-transfer rate across an insulating polyelectrolyte multilayer between the substrate and the P3TOPS layer with modulated electroreflectance. The extent of interpenetration was 8-9 polyelectrolyte layers, the length scale (7-15 nm) depending on the nature of the insulating layer and, especially, on the ionic strength of the solution used for the adsorption of P3TOPS.

Journal Article↗
PubMed2006

Thermal behavior of polyelectrolyte multilayer microcapsules: 2. Insight into molecular mechanisms for the PDADMAC/PSS system.

Polyelectrolyte multilayer capsules consisting of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS) were used as a model system to study the temperature-dependent behavior of polyelectrolyte multilayer films in aqueous media. Shells terminated with PSS shrink upon heating, whereas PDADMAC-terminated ones swell, independent of the nature of the first layer, as measured by means of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Elemental analysis shows that the initial exponential layer growth of the film leads to a nearly neutral overall charge in the first case or a high positive excess charge in the latter. Depending on this overall charge either surface tension, due to an unfavorable polymer-solvent interaction, or electrostatics dominates, resulting in a shrinkage or expansion of capsules, respectively. Thus, it is possible to swell temperature-shrunk capsules by coating them with an additional PDADMAC layer. Micro-DSC measurements prove that polyelectrolyte multilayers undergo a glass transition in water at which the wall material softens, allowing the rearrangements to occur. It is found that the thermal history has an influence on the temperature behavior of capsules, especially on those ones terminated with PDADMAC. Also, the molecular weight of the polyelectrolytes affects the rearrangement of capsules. The lower the molecular weight and thus the smaller the entanglement of chains, the easier polyelectrolytes can rearrange.

Journal Article↗
PubMed2004

Matrix polyelectrolyte microcapsules: new system for macromolecule encapsulation.

A new approach to fabricate polyelectrolyte microcapsules is based on exploiting porous inorganic microparticles of calcium carbonate. Porous CaCO3 microparticles (4.5-5.0 microns) were synthesized and characterized by scanning electron microscopy and the Brunauer-Emmett-Teller method of nitrogen adsorption/desorption to get a surface area of 8.8 m2/g and an average pore size of 35 nm. These particles were used as templates for polyelectrolyte layer-by-layer assembly of two oppositely charged polyelectrolytes, poly(styrene sulfonate) and poly(allylamine hydrochloride). Calcium carbonate core dissolution resulted in formation ofpolyelectrolyte microcapsules with an internal matrix consisting of a polyelectrolyte complex. Microcapsules with an internal matrix were analyzed by confocal Raman spectroscopy, scanning electron microscopy, force microscopy, and confocal laser-scanning fluorescence microscopy. The structure was found to be dependent on a number of polyelectrolyte adsorption treatments. Capsules have a very high loading capacity for macromolecules, which can be incorporated into the capsules by capturing them from the surrounding medium into the capsules. In this paper, we investigated the loading by dextran and bovine serum albumin as macromolecules. The amount of entrapped macromolecules was determined by two independent methods and found to be up to 15 pg per microcapsule.

Animals↗
PubMed2004

Multicompartment films made of alternate polyelectrolyte multilayers of exponential and linear growth.

The layer by layer deposition process of polyelectrolytes is used to construct films equipped with several compartments containing "free polyelectrolytes". Each compartment corresponds to a stratum of an exponentially growing polyelectrolyte multilayer film, and two consecutive compartments are separated by a stratum composed of a linearly growing multilayer that acts as a barrier preventing polyelectrolyte diffusion from one compartment to another. We use hyaluronic acid/poly(L-lysine) as the system to build the compartments and the poly(styrene sulfonate)/poly(allylamine) system for the barrier. Using confocal microscopy, it is shown that poly(L-lysine) diffuses only within the compartment in which it was initially introduced during the film construction and is thus unable to cross the barriers. Using fluorescein isothiocyanate as a pH indicator, it is also shown that although poly(styrene sulfonate)/poly(allylamine) multilayers act as a barrier for polyelectrolytes, they do not prevent proton diffusion through the film. Such films open the route for multiple functionalization of biomaterial coatings.

Journal Article↗