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PubMed1999

Comparison of the Poisson-Boltzmann Model and the Donnan Equilibrium of a Polyelectrolyte in Salt Solution.

A sequence of charged parallel flat plates immersed in a salt solution is used to model the swelling behavior of a polyelectrolyte. The solution of the nonlinear Poisson-Boltzmann equation gives rise to an analytical expression of the plate distance as a function of swelling pressure (p), plate charge density (varsigma), and salt concentration (n). The exact treatment of the system also yields the connection between polyelectrolyte concentration nP, p, varsigma, and n. A formula for the electric potential difference between polyelectrolyte and salt solutions is derived. On the other hand, the relation between nP, p, and n is known from the Donnan equilibrium. It is shown that the Donnan potential, UD(nP, n), and swelling pressure, pD(nP, n), are always larger than the equivalent quantities in the Poisson-Boltzmann theory (UPB(varsigma, nP, n) and pPB(varsigma, nP, n), respectively). The transition from the Poisson-Boltzmann theory to the Donnan model is achieved by the limiting process varsigma --> 0 which reveals the intrinsic linkage between the two theories. pD(nP, n) = limvarsigma-->0 pPB(varsigma, nP, n) and UD(nP, n) = limvarsigma-->0 UPB(varsigma, nP, n). Copyright 1999 Academic Press.

Journal Article↗
PubMed1982

Effect of leukocyte hydrolases on bacteria XVI. Activation by leukocyte factors and cationic substances of autolytic enzymes in Staphylococcus aureus: modulation by anionic polyelectrolytes in relation to survival of bacteria in inflammatory exudates.

The mechanisms involved in the activation of autolytic enzymes in Staphylococcus aureus, by leukocyte extracts, cationic proteins, phospholipase A2, amines, and membrane-damaging agents was studied in a resting cell system as well as by growing staphylococci. The bacteria were labeled with [14C]N-acetylglucosamine and were subjected to a variety of agents either in 0.1 M acetate buffer, pH 5.0, or in phosphate buffer, pH 7.4. While intact log-phase cultures were found to undergo partial autolysis at pH 5.0 and almost complete lysis at pH 7.4, both heat-killed bacteria and bacterial cell walls were completely resistant to autolysis in buffers. Autolysis at pH 5.0 can be further activated by leukocyte extracts, nuclear histone, crystalline ribonuclease, egg-white and human lysozyme, phospholipase A2, as well as by spermine, spermidine, and polymyxins B and E. The addition of viable log-phase bacteria to radiolabeled heat-killed staphylococci or to radiolabeled cell walls which had been cleaned off autolytic enzymes resulted in degradation of the radiolabeled targets. The data suggest that the various inducers of autolysin activation caused leakage of autolytic enzymes from the intact bacteria which attacked the depolymerized the bacterial cell walls. Anionic polyelectrolytes like heparin, dextran sulfate, suramine, polyglutamic acid, and liquid (polyanethole sulfonic acid) markedly inhibited both spontaneous and induced lysis. Staphylococci which had grown in the presence of anionic polyelectrolytes became highly resistant to lysis triggered by any of the inducers of autolysis. Since inflammatory exudates are known to be rich in anionic polyelectrolytes, it is suggested that the prolonged survival of intact bacterial cells in such a milieu may be due to the inactivation of autolytic enzymes. It is also postulated that the degradation of certain bacterial species following phagocytosis or extracellular degradation may not be the result of the action of hydrolytic enzymes but rather the result of activation by leukocyte factors of autolytic enzymes which lead to bacteriolysis.

Bacteriolysis↗
PubMed2006

Optimized coagulation of high alkalinity, low temperature and particle water: pH adjustment and polyelectrolytes as coagulant aids.

The Yellow River in winter as source water is characterized as high alkalinity, low temperature and low particle concentrations, which have brought many difficulties to water treatment plants. This study fully examines the optimized coagulation process of the Yellow River by conventional and pre-polymerized metal coagulants, pH adjustment and polyelectrolytes as the primary coagulants or coagulant aids. For all the metal coagulants, polyaluminum chlorides are superior to traditional metal coagulants due to their stable polymeric species and low consumption of alkalinity. The removal of natural organic matter by monomeric metal coagulants can be improved through pH adjustment, which is in accordance with the higher concentration of polymeric species formed at corresponding pH value. With the addition of polyelectrolytes as coagulant aids, the coagulation performance is significantly improved. The effective removal of dissolved organic matter is consistent with high charge density, while molecular weight is relatively important for removing particles, which is consistent with polyelectrolytes as primary coagulants. These results suggest that the coagulation mechanisms in the removal of dissolved organic matter and particles are different, which may be exploited for optimized coagulation for the typical source water in practice.

Alkalies↗
PubMed1986

Phenotype correction of Ir-genic control of immune response to (T,G)-A-L conjugated to synthetic polyelectrolytes.

Experiments in CBA (H-2k) and C57BL/6 (H-2b) strains of mice have shown (T,G)-A-L covalently bound to synthetic polyelectrolytes possessing immunoadjuvant effect to induce a pronounced antibody and cell-mediated immune response irrespective of murine genotype. When conjugated to the polyelectrolytes (T,G)-A-L was also found to acquire the properties of a highly immunogenic thymus-independent antigen. Thus, (T,G)-A-L-synthetic polyelectrolytes conjugates manifested the effects of highly immunogenic thymus-independent antigens inducing a potent Ir-1-independent immune response. It provided for the transformation of genetically low responder individuals into high responder ones.

Animals↗
PubMed1990

Osmotic flow caused by polyelectrolytes.

Osmotic flow of water caused by high concentrations of anionic polyelectrolytes across semipermeable membranes, permeable only to solvent and simple electrolyte, has been measured in a newly designed flow cell. The flow cell features small solution and solvent compartments and an efficient stirring mechanism. We have demonstrated that, while the osmotic pressure of the anionic polyelectrolytes is determined primarily by micro-counterions, the osmotic flow is determined by solution-dependent properties as embodied in the hydrodynamic frictional coefficient which is determined by the polymer backbone segment of the polyelectrolyte. The variation of the osmotic permeability coefficient, L(p)(o), with concentration and osmotic pressure closely correlated with the concentration dependence of this frictional coefficient. These studies confirm previous work that the kinetics of osmotic flow across a membrane impermeable to the osmotically active solute is primarily determined by the diffusive mobility of the solute.

Journal Article↗
PubMed1991

Polyelectrolytes at the endothelial cell surface.

It is recalled that the tension in a stretched polyelectrolyte chain mechanically compensates both the coulomb interaction and the hydrostatic pressure increase around the chain in a compromise which minimises the free energy and keeps water chemical potential constant throughout. Stretching strongly favors parallel cylinder nematic order in polyelectrolyte brushes on a surface or in the slit between two surfaces when the polyelectrolyte chains function as bridges. Strong, stiffly stretched chains result when the molarity of the fixed charge distribution is larger than the molarity of the neutral salt solution with which the brushes are in equilibrium. The relevance of these two systems to the endothelial cells which cover the walls of blood vessels is discussed.

Cell Membrane↗
PubMed1991

Electroviscosity of polyelectrolyte solutions.

A theoretical expression for the electroviscous effect in polyelectrolyte solutions, caused by the distortion of counterion-distribution and counterion flow around a polyion under a velocity gradient of solvent flow, was obtained to elucidate the characteristic behaviour of the viscosity of highly charged polyelectrolyte solutions observed at low salt concentration. The derivation of the theory was performed on the basis of the Navier-Stokes-Onsager equation, Poisson equation, and diffusion equations for low molecular ions by the use of a cell model (free-volume model) for a polyion. Energy dissipation was obtained without directly solving these equations. It was found that the derived expression of viscosity explained the experimental results satisfactorily, and that the streaming potential effect caused by the counterion flow played an essential role in the increase in viscosity of polyelectrolyte solutions at finite polymer concentration and low salt concentration ranges.

Journal Article↗
PubMed2006

Bioactive coatings based on polyelectrolyte multilayer architectures functionalized by embedded proteins, peptides or drugs.

In recent years, considerable effort has been devoted to the design and controlled fabrication of structured materials with functional properties. The layer by layer buildup of polyelectrolyte multilayer films (PEM films) from oppositely charged polyelectrolytes offers new opportunities for the preparation of functionalized biomaterial coatings. This technique allows the preparation of supramolecular nano-architectures exhibiting specific properties in terms of control of cell activation and may also play a role in the development of local drug delivery systems. Peptides, proteins, chemically bound to polyelectrolytes, adsorbed or embedded in PEM films, have been shown to retain their biological activities.

Coated Materials, Biocompatible↗
PubMed2006

Control of drug accessibility on functional polyelectrolyte multilayer films.

A surface coating based on polylysine/hyaluronic acid multilayers was designed and acted as a reservoir for an antiproliferative agent, paclitaxel (Taxol). Absolutely no chemical modification of polyelectrolytes or of the drug was needed and the final architecture was obtained in an extremely simple way using the layer-by-layer method. The paclitaxel dose available for human colonic adenocarcinoma cells HT29 seeded on the films could be finely tuned. Moreover, the accessibility of the drugs was controlled by adding on the top of the drug reservoir a capping made of synthetic polyelectrolyte multilayers. This capping was also required to allow adhesion of HT29 cells. Paclitaxel activity was maintained after embedding in the polyelectrolyte multilayers and cellular viability could be reduced by about 80% 96 h after seeding. The strategy described in this paper could be valuable for various other drug/cell systems.

Antineoplastic Agents, Phytogenic↗
PubMed2006

Cytotoxicity of polyethyleneimine (PEI), precursor base layer of polyelectrolyte multilayer films.

Polyethyleneimine (PEI) is a synthetic polymer commonly used as precursor base layer in polyelectrolyte multilayer films. However, the biological properties of this cationic macromolecule are poorly understood. The aim of this experimental investigation was to evaluate in vitro the biocompatibility of PEI towards two different human cell lines. The experimental investigation was undertaken on pure titanium (Ti) and nickel-titanium (NiTi) alloy samples with an average surface roughness of Ra=0.3microm. A biological study was undertaken at day 0 (2h after seeding), day 2, day 4 and day 7 to observe the cellular response of fibroblasts and osteoblasts cell lines in terms of morphology, adhesion (as observed by scanning electron microscopy), and viability (Mosmann's test). The results showed that PEI can be successfully deposited onto Ti or NiTi alloy, but generates a detrimental cellular response on both substrates as illustrated by a decrease of both fibroblast and osteoblast adhesion and proliferation over a 7-day culture period. These results suggest that PEI is potentially cytotoxic and may not be biocompatible enough in clinical applications using high molecular weight. As a consequence, polyelectrolyte multilayer films, which are promising in prosthesis and implantology fields, could not be coated with PEI at a high molecular weight. A lower molecular weight should be considered or a more biocompatible molecular base as precursor layer of polyelectrolyte multilayer films would be better to use for a good human bio-integration.

Cell Shape↗
PubMed2006

Formation of polyelectrolyte-surfactant complexes on surfaces.

The interfacial behavior of polyelectrolytes, mainly cationic with varying content of amphiphilic groups, and their complexes with oppositely charged surfactant are discussed. Both the kinetics and the reversibility aspect of the adsorption are considered. The structure of adsorbed layer formed was found to be dependent not only on the bulk solution phase behavior, but also on the pre-applied conditions, i.e., the path used to obtain a particular solution condition (e.g., by changing pH and concentration of salt, surfactant or polymer). Polyelectrolyte adsorption appears only partly reversible, due to its high affinity to the surface, which slows down the adsorption process. In general, relaxation occurs more easily if the direction of the process is from low to high surface coverage. Association of the surfactant with the polymer, which depends on the surfactant concentration, can completely alter the interfacial behavior. Maximum adsorption occurs generally at a surfactant concentration just before the expected phase separation region, while the complex in some cases could desorb from the surface at high enough surfactant concentration (above the cmc). Different results were obtained for coadsorption of amphiphilic polyelectrolytes when surfactant was added to the preadsorbed polymer layers and when complexes were pre-formed in the solution prior to exposing the surface to the polymer-surfactant solution.

Adsorption↗
PubMed2005

Combination of adsorption by porous CaCO3 microparticles and encapsulation by polyelectrolyte multilayer films for sustained drug delivery.

Combination of adsorption by porous CaCO(3) microparticles and encapsulation by polyelectrolyte multilayers via the layer-by-layer (LbL) self-assembly was proposed for sustained drug release. Firstly, porous calcium carbonate microparticles with an average diameter of 5 microm were prepared for loading a model drug, ibuprofen (IBU). Adsorption of IBU into the pores was characterized by ultraviolet (UV), infrared (IR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) experiment and X-ray diffraction (XRD). The adsorbed IBU amount Gamma was 45.1mg/g for one-time adsorption and increased with increasing adsorption times. Finally, multilayer films of protamine sulfate (PRO) and sodium poly(styrene sulfonate) (PSS) were formed on the IBU-loaded CaCO(3) microparticles by the layer-by-layer self-assembly. Amorphous IBU loaded in the pores of the CaCO(3) microparticles had a rapider release in the gastric fluid and a slower release in the intestinal fluid, compared with the bare IBU crystals. Polyelectrolyte multilayers assembled on the drug-loaded particles by the LbL reduced the release rate in both fluids. In this work, polymer/inorganic hybrid core-shell microcapsules were fabricated for controlled release of poorly water-soluble drugs. The porous inorganic particles are useful to load drugs in amorphous state and the polyelectrolyte multilayer films coated on the particle assuage the initial burst release.

Adsorption↗
PubMed2004

Ionizable polyelectrolyte brushes: brush height and electrosteric interaction.

Semi-analytical scaling theory is used to describe quenched and annealed (weakly charged, ionizable, charge-regulating) polyelectrolyte brushes in electrolyte solutions of arbitrary salt concentration. An Alexander-De Gennes box model with homogeneous distribution of polymer segments and the free ends located at the edge of the brush is assumed, as is local electroneutrality in the brush. For annealed polyelectrolyte and in the low-salt regime, the theory predicts that for sufficiently dense brushes, the salt concentration has a small influence on brush height, while the brush expands with increasing grafting density, in agreement with experiment. Expressions are presented for the interaction free energy of compressed ionizable and quenched polyelectrolyte brushes (proportional to the force between particles or curved surfaces). In all cases, the required prefactors are explicitly stated. The theory is compared directly with published experiments on the influence of salt concentration, pH, and grafting density on the thickness and interaction force of polystyrene sulfonate (quenched) and poly(meth)acrylic acid (annealed) brushes. In general, trends are well reproduced but significant deviations remain.

Journal Article↗
PubMed2004

Comparison of the shape parameters of DNA-cationic lipid complexes and model polyelectrolyte-lipid complexes.

In this study, we used a rheological method to study the shape of DNA-cationic lipid complexes and model polyelectrolyte-lipid complexes. We introduced two kinds of anionic polyelectrolytes, sodium polygalacturonate (PGU) and sodium dextran sulfate (DSS), of varying size, as models for DNA. The prepared complexes were incubated under laminar flow conditions. The results show the same quantitative relation between the shape parameter of lipoplexes and the length of anionic polyelectrolytes, including DNA. The rheological behavior of PGU and DSS were similar to that of DNA.

Anions↗
PubMed2004

Effect of shear stress on adhering polyelectrolyte capsules.

A parallel plate flow chamber was implemented to study the deformation and adhesion of individual spherical hollow polyelectrolyte multilayered shells adhering to a coated surface. The device provides a well-defined laminar flow allowing the determination of the shear stress to which the capsules are being exposed up to 15 N/m(2). The results of the investigations indicate a strong dependence of the adhesion and mechanical resistance on the capsule size and wall thickness. Thin walled capsules, constituted of 8 polyelectrolyte layers (thickness congruent with 12 nm), are immediately deformed when exposed to flow while thick capsules, constituted of 16 layers (thickness congruent with 24 nm), of equal dimensions are detached from the surface for drag forces below 50 nN. It was observed that adhering capsules exposed to flow undergo an increase in their adhesion area in the direction of flow, resulting in rolling of the capsules. It was also found that the resistance of the capsules decreases after acetone treatment, indicating a weakening of the polyelectrolyte multilayer structure in the presence of this solvent.

Journal Article↗
PubMed2005

Effect of surfactant head group size on polyelectrolyte-surfactant interactions: steady-state and time-resolved fluorescence study.

Interactions between sodium poly(acrylate) (NaPAA) and dodecyltrimethyl/ethyl/propyl/butylammonium bromide (C12NM, C12NE, C12NP, and C12NB) were studied. Variation of the physicochemical properties of the surfactants and polyelectrolyte-surfactant mixtures, such as critical micelle concentration (cmc), critical aggregation concentration (cac), micellar micropolarity, aggregation number, and pyrene lifetime, were determined by steady-state and time-resolved fluorescence methods. It is shown that the surfactant head group size has a striking effect on the interaction between surfactant and polyelectrolyte. The interaction is weakened gradually when the surfactant head group is increased from trimethyl to tripropyl, which might be owing to the increase of the steric hindrance between the polyelectrolyte chain and micellar surface. But when the head group is tributyl, the interaction is enhanced and stronger than that between C12NP and NaPAA. This might be explained by the self-association of the C12NB head groups.

Electrolytes↗
PubMed2005

In situ determination of thickness and electrical properties of multilayers from weak polyelectrolytes.

An electro-optical study of the role that the outermost layer plays in the behavior of a multilayer film of the weak polyelectrolytes poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) was carried out. The film surface was enriched with the chains of the last adsorbed polyelectrolyte when a fully ionized polymer was combined with nearly fully charged chains of the other polyelectrolyte. A distinct influence of the chain length on the critical frequency of relaxation of the electro-optical effect was demonstrated, indicating that polarization of condensed counterions of the last adsorbed polymer governs the behavior of the whole film. The multilayer growth, which was found to proceed via a series of adsorption-desorption steps, correlated well with the changes in the electro-optical effect. No indication was found, however, for participation of small ions from the film bulk in creation of the electro-optical effect.

Journal Article↗
PubMed2006

Salt effect on the interactions between gemini surfactant and oppositely charged polyelectrolyte in aqueous solution.

The effect of alkali halides (NaBr, NaCl, KCl) on the interactions between the cationic gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and the anionic polyelectrolyte sodium polyacrylate (NaPAA) in aqueous solution has been investigated by fluorescence emission spectroscopy, UV transmittance, zeta potential, and transmission electron microscopy (TEM). With increased addition of NaBr, a counterbalancing salt effect on the critical aggregation concentration (CAC) is observed. At low concentrations, NaBr facilitates the formation of micelle-like structures between surfactant and polyelectrolyte and results in a smaller CAC. At high concentrations, NaBr screens the electrostatic attraction between surfactant and polyelectrolyte and leads to a larger CAC. Upon the formation of micelle-like structures at high surfactant concentrations, the addition of NaBr is favorable for larger aggregates. The microstructure detected by TEM show that a global structure is generally formed in the presence of NaBr. The interactions also depend on ion species. Compared to NaBr, the addition of NaCl or KCl yields a smaller CAC.

Journal Article↗