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PubMed2004

Induced crystallization of polyelectrolyte-surfactant complexes at the gas-water interface.

Synchrotron x-ray and surface-tension studies of a strong polyelectrolyte (PE) in the semidilute regime (approximately 0.1 M monomer charges) with varying surfactant concentrations show that minute surfactant concentrations induce the formation of a PE-surfactant complex at the gas-solution interface. X-ray reflectivity and grazing angle x-ray diffraction show the complex PE-surfactant resides at the interface and the alkyl chains of the surfactant form a two-dimensional liquidlike monolayer. With the addition of salt (NaCl), columnar crystals with distorted-hexagonal symmetry are formed.

Crystallization↗
PubMed2005

Stratification kinetics of polyelectrolyte solutions confined in thin films.

We have studied free horizontal liquid films made with semidilute polyelectrolyte solutions. A stratification phenomenon is observed during film thinning, with a step size close to the mesh size of the polymer network: dark domains nucleate and expand, the outer polymer layer dewetting a thinner film. The kinetics of dark spot expansion is not simply related to bulk viscosity and becomes faster when the film thickness decreases, suggesting an increase of the chain mobility of the confined polymer chains. These findings are similar to recent ones for other confined liquids and are the first reported so far for freely standing films.

Electrolytes↗
PubMed2006

Critical adsorption of polyelectrolytes onto charged spherical colloids.

The adsorption of a flexible polyelectrolyte in a salt solution onto an oppositely charged spherical surface is investigated. An analytical solution is derived, which is valid for any sphere radius and consistently recovers the result of a planar surface in the limit of large sphere radii, by substituting the Debye-Hückel potential via the Hulthén potential. Expressions for critical quantities such as the critical radius and the critical surface charge density are provide. A comparison of our theoretical results with experiments and computer simulations yields remarkable good agreement.

Journal Article↗
PubMed2006

Salt-induced swelling-to-shrinking transition in polyelectrolyte multilayer capsules.

We study the size of polyelectrolyte multilayer capsules as a function of ionic strength, temperature, and time. A dynamic micromechanical model is developed which successfully describes the experiments. The model includes the polymer-solvent surface tension, an electrostatic force which is strongly ionic strength dependent, and a temperature-dependent mobility parameter. The activation of >50 kT suggests that multiple ion pairs must be broken simultaneously in the process of chain rearrangement. In support of our physical model capsules can repeatedly swell and shrink by varying ionic strength.

Journal Article↗
PubMed2004

Microstructuring of polyelectrolyte coated surfaces for directing capsule adhesion.

We use microcontact printing (microCP) of polyelectrolytes (PEs) onto flat substrates for creating surfaces with regions of negative and positive surface charge. Subsequent incubation of these surfaces with solutions containing hollow PE capsules leads to preferential adsorption of the capsules on regions of opposite charge, while regions of like charge are passivated against adhesion. As well, adsorption of fluorescently labeled PEs is found to be directed toward oppositely charged regions at neutral pH. This approach could lead to novel functional surfaces for combinatorial chemistry or sensor applications and could also be expanded toward cell immobilization.

Adsorption↗
PubMed2005

Cellular response to gelatin- and fibronectin-coated multilayer polyelectrolyte nanofilms.

Surface engineering is a critical effort in defining substrates for cell culture and tissue engineering. In this context, multilayer self-assembly is an attractive method for creating novel composites with specialized chemical and physical properties that is currently drawing attention for potential application in this area. In this work, effects of thickness, surface roughness, and surface material of multilayer polymer nanofilms on the growth of rat aortic smooth muscle cells were studied. Polyelectrolyte multilayers (PEMs) electrostatically constructed from poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) (PSS) with gelatin, fibronectin, and PSS surface coatings were evaluated for interactions with smooth muscle cells (SMCs) in an in vitro environment. The results prove that PEMs terminated with cell-adhesive proteins promote the attachment and further growth of SMCs, and that this property is dependent upon the number of layers in the underlying multilayer film architecture. Cell roundness and number of pseudopodia were also influenced by the number of layers in the nanofilms. These findings are significant in that they demonstrate that both surface coatings and underlying architecture of nanofilms affect the morphology and growth of SMCs, which means additional degrees of freedom are available for design of biomaterials. This work supports the excellent potential of nanoassembled ultrathin films for biosurface engineering, and points to a novel perspective for controlling cell-material interaction that can lead to an elegant system for defining the extracellular in vitro environment.

Animals↗
PubMed1982

Response to infusions of polyelectrolyte fractionated human factor VIII concentrate in human haemophilia A and von Willebrand's disease.

Factor VIII was purified from cryoprecipitate by ion exchange chromatography on solid phase polyelectrolyte E-5 (PE-E5). The product was highly purified (3.5 u VIII:C/mg protein) compared to conventional concentrate (0.3 u VIII:C/mg protein) with low fibrinogen, low isoagglutinin titre, and a ratio of factor VIII coagulant activity (VIII:C) to factor VII related antigen (VIIIR:Ag) of 16:1. Trial infusions of this material (PE VIII) were given to three patients with severe haemophilia A and one patient with homozygous von Willebrand's disease. These patients also each received separate infusions of intermediate purity concentrate (IPC) for comparison. There were no adverse effects. The mean half life of VIII:C after PE VIII infusion in the haemophiliacs was 10.9 h and after IPC was 12.1 h, a statistically insignificant difference. The survival of factor VIII coagulant antigen (VIII:CAg) was similar to that of VIII:C. In contrast, the half life of VIII:C and of VIII:CAg was very short after infusion of PE VIII in the patient wih von Willebrand's disease (2.4 h). IPC when infused in this patient produced a typical secondary rise of VIII:C. Two bleeding episodes in severe haemophiliacs were satisfactorily treated with PE VIII. PE-E5 deserves further study as a means of preparing clinical concentrates of factor VIII.

Antigens↗
PubMed1979

Freedom from transmission of hepatitis-B of gamma-globulin and heat-inactivated plasma protein fraction prepared from contaminated human plasma by fractionation with solid-phase polyelectrolytes.

Plasma contaminated with hepatitis B surface antigen (HBsAg) and shown by others to be infectious when injected in a dilution of 1:1,000,000 in chimpanzees, was fractionated by a solid-phase polyelectrolyte (PE) procedure for its content of plasma protein fraction (PPF) and gamma-globulin (immune serum globulin; ISG). Quantitative Ausria II radioimmunoassays showed that nearly half the HBsAg was bound by the PE and could be eluted at low pH, while the rest was found in the heat-inactivated PPF. When the ISG was concentrated to 16%, the 13 mg/kg (comparable to a human dose) was injected intramuscularly in 6 chimpanzees, or when the PPF was heated at 60 degrees C for h and injected intravenously in 2 chimpanzees, there was no clinical or laboratory evidence of hepatitis B infection after 12 months, although 1 chimp of 2 who received the same material showed a borderline positive anti-HBsAg antibody result on one of 52 weekly serum samples. Since the new PE fractionation method is essentially nondenaturing, and simpler than the classical ethanol procedures, it was important to establish the noninfectivity of the final products.

Adsorption↗
PubMed1985

Enzymes in polyelectrolyte complexes. The effect of phase transition on thermal stability.

Penicillin amidase, alpha-chymotrypsin and urease have been immobilized in water-soluble nonstoichiometric polyelectrolyte complexes (N-PEC). N-PEC are formed by modified poly(N-ethyl-4-vinyl-pyridinium bromide) (polycation) and excess poly(methylacrylic acid) (polyanion). N-PEC are a new class of polymers capable, characteristically, of phase transitions solution in equilibrium precipitate induced by slight change in pH or ionic strength. Neither the chemical structure of the carrier nor the number of cross-linkages between an enzyme and a carrier change on phase transition. That gives an unique opportunity to elucidate the difference between enzymes immobilized on water-soluble and water-insoluble supports. A detailed study of the phase transition effect on thermal stability of the enzymes and protein-protein interactions has been carried out. The following effects were found. Pronounced thermal stabilization of penicillin amidase and urease may be achieved on two conditions: the enzyme is in the precipitate; (b) the enzyme is linked to the N-PEC nucleus. Then the thermal stability of N-PEC-bound penicillin amidase increases 7-fold at pH 5.7, 60 degrees C, and 300-fold at pH 3.1, 25 degrees C, compared to the native enzyme. For urease, the thermal stabilization increases 20-fold at pH 5.0, 70 degrees C. The localization of enzyme on N-PEC has been established by titration of alpha-chymotrypsin bound to a polycation or polyanion with basic pancreatic trypsin inhibitor. Both in solution (pH 6.1) and in N-PEC precipitate (pH 5.7), an alpha-chymotrypsin molecule bound to a polyanion is fully exposed to the solution. If the enzyme is bound to a polycation, only 20% of alpha-chymotrypsin molecules in the precipitate and 40% in solution retain their ability for protein-protein interactions. This means that a polycation-bound enzyme is localized in the hydrophobic nucleus of the complex, whereas the polyanion-bound enzyme sits on the hydrophilic shell of the complex. On pH-induced phase transition (pH decreases from 6.1 to 5.7), there occurs a stepwise decrease in penicillin amidase activity which is due to a 9.8-fold increase in the Km for 2-nitro-4-phenylacetamidobenzoic acid. Change of the catalytic activity and thermal stability of N-PEC-bound penicillin amidase is fully reversible and reproducible. Such soluble-insoluble immobilized enzymes with controllable thermal stability and activity may be used for simulating events in vivo and in biotechnology.

Chymotrypsin↗
PubMed2001

Optimal conditions of transplantable binary polyelectrolyte microcapsules.

Binary polyanion/oligocation microcapsules, prepared in a one-step process, are proposed as an alternative to the common alginate/poly-L-lysine system used in bioencapsulation technology. The model system is based on natural polysaccharides and involves the anionic sodium alginate, or iota-carrageenan, complexed with cationic oligochitosan. This system has been characterized with respect to capsule formation, mechanical strength, and permeability. This paper provides a general description of the influence of the most pronounced parameters that can be used as a tool to modulate the properties of binary microcapsules. These parameters have been separated into two categories. The first, which includes molar mass of polyanion, pH, ionic strength, and concentration of both polyelectrolytes, can be used to simultaneously control capsule mechanical and structural properties. The second set, molar mass of polyanion and reaction time, influences only mechanical resistance without altering membrane permeability. Additional issues related to mechanical stability and the possible change of capsule properties following transplantation are discussed.

Animals↗
PubMed2004

Multilayer polyelectrolyte films functionalized by insertion of defensin: a new approach to protection of implants from bacterial colonization.

Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic surgery. In the present study, we developed a new strategy based on the insertion of an antimicrobial peptide (defensin from Anopheles gambiae mosquitoes) into polyelectrolyte multilayer films built by the alternate deposition of polyanions and polycations. Quartz crystal microbalance and streaming potential measurements were used to follow step by step the construction of the multilayer films and embedding of the defensin within the films. Antimicrobial assays were performed with two strains: Micrococcus luteus (a gram-positive bacterium) and Escherichia coli D22 (a gram-negative bacterium). The inhibition of E. coli D22 growth at the surface of defensin-functionalized films was found to be 98% when 10 antimicrobial peptide layers were inserted in the film architecture. Noticeably, the biofunctionalization could be achieved only when positively charged poly(l-lysine) was the outermost layer of the film. On the basis of the results of bacterial adhesion experiments observed by confocal or electron microscopy, these observations could result from the close interaction of the bacteria with the positively charged ends of the films, which allows defensin to interact with the bacterial membrane structure. These results open new possibilities for the use of such easily built and functionalized architectures onto any type of implantable biomaterial. The modified surfaces are active against microbial infection and represent a novel means of local host protection.

Adsorption↗
PubMed1971

Concentration and purification of viruses by adsorption to and elution from insoluble polyelectrolytes.

Acid-resistant, nonenveloped viruses belonging to the enterovirus, reovirus, and adenovirus groups were readily concentrated on PE60, an insoluble cross-linked polyelectrolyte based on isobutylene maleic anhydride. Hydrolysis of PE60 by NaOH increased its capacity to adsorb viruses. Hydrogen ion levels played an important role in virus concentration; optimal pH levels for maximal virus adsorption were between pH 3.0 and 4.5. Undiluted virus was easily concentrated from large volumes on PE60, and the adsorbed virus was readily eluted at pH 8 to 9.

Adenoviridae↗
PubMed1972

Use of polyelectrolytes and electron microscopy for detection of viruses from stool.

Insoluble polyelectrolytes (PE60) were used for the concentration of viruses from stool specimens, confirming the results of Wallis et al. (1969). Ten percent suspensions inoculated with poliovirus type 3 were used in these experiments. A small number of stool specimens from patients naturally infected with enteroviruses were also tested. Preferential adsorption of viruses to PE60 was maximum at a pH range of 4.5 to 6.0. The elution of the adsorbed viruses was optimal at pH 8.5. Other parameters were also investigated. Electron microscopy was used successfully to detect the eluted viruses.

Adsorption↗
PubMed1976

Comparison of talc-Celite and polyelectrolyte 60 in virus recovery from sewage: development of technique and experiments with poliovirus (type 1, Sabin)-contaminated multilitre samples.

For virus recovery from sewage, a mixture of talc and Celite was tested as a possible inexpensive substitute for polyelectrolyte 60 (PE 60). After adjustment of pH to 6 and the addition of 45-60 plaque forming units (PFU)/ml of poliovirus type I (Sabin) to the sewage sample under test, 100 ml of it was passed through either a PE 60 (400 mg) or a talc (300 mg)-Celite (100 mg) layer; the layer-adsorbed virus was eluted with 10 ml of 10% fetal calf serum (FCS) in saline (pH 7.2). In these experiments, PE 60 layers recovered 73-80% (mean 76%) of the input virus. In comparison, virus recoveries with the talc-Celite layers were 65-70% (mean 68%). Passage of 5 litres of raw sewage (containing 50 to 1.26 X 10(5) PFU/100 ml of the poliovirus) through the talc (15 g)-Celite (5 g) layers and virus elution with 50 ml of 10% FCS in saline gave virus recoveries of 33-63% (mean 49%). Except for pH adjustment and prefiltration through two layers of gauze to remove large solids, no other sample pretreatment was found to be necessary. Application of this technique to recovery of indigenous viruses from field samples of raw sewage and effluents has been highly satisfactory.

Adsorption↗
PubMed2003

Persistence length for a model semirigid polyelectrolyte as seen by small angle neutron scattering: a relevant variation of the lower bound with ionic strength.

In a SANS experiment, we have directly determined for the first time the conformation of hyaluronan, a model semirigid polyelectrolyte. At high ionic strength, this is completely possible, where the scattered intensity crosses over (when decreasing q) from a q(-1) rod variation to a q(-2) and, where fitting to the "wormlike" chain model gives the backbone, intrinsic, persistence length: L0 = 86.5 A. At low ionic strength, we can safely check that the measured persistence length appears increased by at least the amount predicted by Odijk for the electrostatic contribution, L(e) (approximately kappa(-2), square of the Debye screening length). However, the intensity at the lowest q is not only due to the single chain, since it crosses over from a q(-1) to a q(-4) variation, characteristic of polymer associations.

Journal Article↗
PubMed2004

Water-dispersed lamellar phases of symmetric poly(styrene)-block-poly(acrylic acid) diblock copolymers: model systems for flat dense polyelectrolyte brushes.

We investigate the static properties of a water-dispersed lamellar ( L) phase formed in the melt state with a nearly symmetric poly(styrene)-block-poly(acrylic acid) (PS- b-PAA) diblock copolymer. The PAA brush is considered as a model flat polyelectrolyte ( PE) brush of controlled surface density. Thanks to small-angle X-ray scattering, its behavior in water is studied as a function of (i) its ionization, through the pH of the dispersions which is increased by an addition of a known amount of a base, i.e. sodium hydroxyde NaOH, and (ii) in the presence of a monovalent salt, i.e. sodium chloride NaCl, of concentration C(S). At low pH, we find that the brush effectively behaves as a neutral brush. At high pH, the brush is in the so-called "osmotic regime", in which all sodium counterions are trapped within the brush volume and stretch the chains via an osmotic effect. The properties of such a brush in the presence of a monovalent salt, confirm this result, showing a C(S)(-1/3) dependence in the brush height L(O), in agreement with mean-field predictions. The L(O)- C(S) profiles at different ionizations give access to the actual brush internal charge fraction f. The results are found to be in very good quantitative agreement with experimental measures found in the literature, and can be completely and quantitatively described by Oosawa's approach to counterion condensation in a semi-dilute to concentrated solution of charged, rod-like chains.

Acrylic Resins↗
PubMed2002

Equilibrium charge distribution on annealed polyelectrolytes.

Monte Carlo simulations are used to study the non-uniform equilibrium charge distribution along a single annealed polyelectrolyte chain under theta solvent conditions and with added salt. Within a range of the order of the Debye length charge accumulates at chain ends while a slight charge depletion appears in the central part of the chain. The simulation results are compared with theoretical predictions recently given by Castelnovo et al. In the parameter range where the theory can be applied we find almost perfect quantitative agreement.

Journal Article↗
PubMed2002

Monte Carlo simulations of star-branched polyelectrolyte micelles.

The concentration profiles of monomers and counterions in star-branched polyelectrolyte micelles are calculated through Monte Carlo simulations, using the freely jointed chain model. We have investigated the onset of different regimes corresponding to the spherical and Manning condensation of counterions as a function of the strength of the Coulomb coupling. The Monte Carlo results are in fair agreement with the predictions of Self-Consistent-Field analytical models. We have simulated a real system of diblock copolymer micelles of (sodium-polystyrene-sulfonate)(NaPSS)-(polyethylene-propylene)(PEP) with f = 54 hydrophilic branches of N = 251 monomers at room temperature in salt-free solution. The calculated form factor compares nicely with our neutron scattering data.

Journal Article↗