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PubMed2006

Light scattering study of complex formation between protein and polyelectrolyte at various ionic strengths.

Formation of protein-polyelectrolyte complexes (PPCs) between bovine serum albumin (BSA) and potassium poly (vinyl alcohol) sulfate (KPVS) was studied at pH 3 as a function of ionic strength. Turbidimetric titration was employed by a combination of dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The formal charge (Z(PPC)) of the resulting PPCs at different ionic strengths were estimated from ELS data by assuming the free draining and the non-free draining model. The radius of a BSA molecule in the complex was used in the former model for calculation of Z(PPC) with the Henry's equation, while in the latter case the hydrodynamic radius of a PPC particle determined from DLS was employed. The results obtained were compared with the Z(PPC) values calculated using a relation of Z(PPC)=n(b)Z(BSA)+alphaZ(KPVS), where Z(BSA) (> or =0) and Z(KPVS) (< or =0) denote the formal charge of BSA and KPVS, respectively. Moreover, n(b) is the number of bound proteins per complex composed of alpha polymer chains. It was suggested that the PPC between BSA and KPVS behaves as a free draining molecule during the electrophoresis, at least at a high ionic strength. Also suggested is that the PPC formation at low ionic strength follows a 1:1 stoichiometry in the charge neutralization.

Animals↗
PubMed2006

Surface modification of poly(tetramethylene adipate-co-terephthalate) membrane via layer-by-layer assembly of chitosan and dextran sulfate polyelectrolyte multiplayer.

The improvement of hydrophilicity and hemocompatibility of poly(tetramethylene adipate-co-terephthalate) (PTAT) membrane was developed via polyelectrolyte multilayers (PEMs) immobilization. The polysaccharide PEMs included chitosan (CS, as a positive-charged and antibacterial agent) and dextran sulfate (DS, as a negative-charged and anti-adhesive agent) were successfully prepared using the aminolyzed PTAT membrane in a layer-by-layer (LBL) self-assembly manner. The obtained results showed that the contact angle of as-modified PTAT membranes reached to the steady value after four bilayers of coating, hence suggesting that the full coverage was achieved. It could be found that the PTAT-PEMs membranes with DS as the outmost layer could resist the platelet adhesion and human plasma fibrinogen (HPF) adsorption, thereby prolonging effectively the blood coagulation times. According to L929 fibroblast cell growth inhibition index, the as-prepared PTAT membranes exhibited non-cytotoxic. Overall results demonstrated that such an easy, valid and shape-independent processing should be potential for surface modification of PTAT membrane in the application of hemodialysis devices.

Adipates↗
PubMed2006

Surface sliding friction of negatively charged polyelectrolyte gels.

The friction between two polyelectrolyte gels carrying the same or opposite sign of charges has been investigated using a rheometer. It is found that the friction was strongly dependent on the interfacial interaction between two gel surfaces. In the repulsive interaction case, especially, the friction was extremely low. The friction behavior is attempted to be described in terms of the hydrodynamic lubrication of the solvent layer between two like-charged gel surfaces, which is formed due to the electrostatic repulsion of the two gel surfaces. From the theoretical analysis (hydrodynamic mechanism), the friction behaviors were explained qualitatively, all of the experimental results, nevertheless, could not be understood well. The viscoelastic feature of the gel and the non-Newtonian behavior of water at the friction interface are considered to be important to elucidate the gel friction.

Acrylamides↗
PubMed2006

Lower critical solution temperature type of phase separation in aqueous mixture of polyelectrolytes.

Phase separation behavior in aqueous mixture of different polyelectorolytes having like charges has been investigated as functions of concentration and charge density. When the charge densities of both polyelectorolytes were equally high, the compatibility between different polyelectorolytes was relatively good and the phase separation behavior was a normal upper critical solution temperature (UCST) type. With decreasing the charge density of one polyelectorolyte keeping the charge density of another polyelectrolyte unchanged, the compatibility between different polyelectorolytes became poorer. When the charge density of one polyelectorolyte was lowered below a certain value, the phase separation behavior suddenly changed from the UCST type to a lower critical solution temperature (LCST) type.

Electrolytes↗
PubMed2006

A mycelium with polyelectrolyte complex-bunched hyphae: preparation and fermentation performance.

We studied the immobilization of a mycelium (Aspergillus niger) using the working hypothesis as follows: (a) when polycation was added to the cell suspension, a few parts of it would bind on the surface of a hypha, allowing to gather the hyphae in part but not all; (b) upon further addition of polyanion, such a gathering of the hyphae is tightly bunched by the polyelectrolyte complex (PEC) which is resulted from the remaining polycation; (c) as a result, a mycelium with partially bunched hyphae can be obtained. Potassium poly(vinyl alcohol) sulfate and trimethylammonium glycol chitosan iodide [6-O-(2-hydroxyethyl-2-(trimethylamonio)-chitosan iodide) were used as the polyanion and the polycation, respectively. The optical and electron microscopic analyses showed that our immobilized cell contains many of PEC-bunched hyphae. The sedimentation rate increased with the weight ratio of PEC to dry cells and leveled off at the weight ratio larger than 0.5. The gluconic acid production from glucose was studied by a semi-large scale (1l) cultivation of the imobilized and free cells using a jar fermentor. It was found that an apparent specific activity of the immobilized cells for glucose oxidation becomes 1.44 times that of the free cells even at a high cell density of 40 g/l.

Adsorption↗
PubMed2006

Reversed chitosan-alginate polyelectrolyte complex for stability improvement of alpha-amylase: optimization and physicochemical characterization.

The present work explores, using response surface methodology, the main and interaction effects of some process variables on the preparation of a reversed chitosan-alginate polyelectrolyte complex (PEC) with entrapped alpha-amylase for stability improvement. A 3(3) full factorial design was used to investigate the effect of the chitosan and alginate concentrations and hardening time on the percent entrapment, time required for 50% (T(50)) and 90% (T(90)) enzyme release, and particle size. The beads were prepared by dropping chitosan containing alpha-amylase into a sodium alginate solution without any salt. The in vitro enzyme release profile of the beads was fitted to various release kinetics models to study the release mechanism. A topographical characterization was carried out using scanning electron microscopy (SEM), and the entrapment was confirmed using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zones III and IV. Beads prepared using 2.5%w/v chitosan and 3%w/v sodium alginate with a hardening time of 60 min had more than 90% entrapment and a T(90) value greater than 48 min. Moreover, the shelf-life of the enzyme-loaded beads was found to increase to 3.68 years, compared with 0.99 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare a reversed PEC of chitosan and alginate with good mechanical strength, provided both the reactants are in a completely ionized form at the time of the reaction. Proper selection of the reaction pH, polymer concentration and hence charge density, and hardening time is important and determines the characteristics of the PEC.

Alginates↗
PubMed2006

Preparation and characterization of biocompatible polyelectrolyte complex multilayer of hyaluronic acid and poly-L-lysine.

A novel biocompatible polyelectrolyte complex multilayer (PECML) was successfully prepared using hyaluronic acid (HA) and poly-l-lysine (PLL). The formation of PECML through the electrostatic interaction of HA as a polyanion and PLL as a polycation was confirmed by contact angle measurement, ESCA analysis and HA content analysis. According to the Carbazole assay, HA content increased rapidly up to eight cycles for HA/PLL deposition and then slightly increased with an increasing number of deposition cycle. In vitro release of PLL from the PECML continued up to 4 days exhibiting different release profiles depending on the outer layer of PECML. This result provides evidence for PLL diffusion throughout PECML of HA and PLL during the multilayer buildup. About 25% of HA remained on the cover glass after the in vitro release test for 7 days. From the results, we confirmed that PECML of HA and PLL could remain at least partially on the chitosan-coated cover glass for 7 days. The surface modification with PECML resulted in drastically reduced peripheral blood mononuclear cell (PBMC) attachment according to the lactate dehydrogenase assay for cell counting. This nano-scale control of material deposition may be successfully applied for surface modification of various biomaterials.

Cell Adhesion↗
PubMed2004

The improvement of aqueous chemical stability of a model basic drug by ion pairing with acid groups of polyelectrolytes.

Carbomer (C) and procaine (P) were selected respectively as models of polyelectrolyte (PE) and basic drug (B) of low stability in aqueous solution. The purpose of this investigation was to test if a (C-P) aqueous system provides a microenvironment in which P is less exposed to hydroxyl ion catalyzed degradation, its main degradation pathway over a wide pH range. It was determined that in (C-P) a high fraction of P was present in the form of ion pairs [RCOO-PH+] with the carboxylate groups of C. The [RCOO-PH+] fraction was above 97% for compositions containing higher than 50 mol% of P. The chemical stability of C-P was assayed at two selected pHs (7.5 and 8.5) in comparison with conventional reference solutions (RS) without C. Procaine in (C-P) was 4.2 and 6.2 times more stable than in its respective RS at the two conditions assayed. The stabilizing factor was calculated as the ratio of the rate constants k(obs)(RS)/k(obs)(C-P).Since C-B systems exhibit negative electrokinetic potential that attracts positive ions such as (H+) and repels negative ones such as (OH(-)), the stabilizing effect would be associated with the higher acidity of (C-P) environment, in which PH+ molecules attached to the PE should also have lower kinetic energy than those in the bulk medium.

Acrylic Resins↗
PubMed2005

Swellable drug-polyelectrolyte matrices (SDPM). Characterization and delivery properties.

The objective of the study is to develop and characterize the delivery properties of swellable drug-polyelectrolyte matrices (SDPM). Solid complexes (C-D)X of carbomer (C) neutralized with different proportions of model basic drugs (D), in which D is atenolol, lidocaine, and metoclopramide, and X=25, 50, 75 and 100 mol of D per 100 equivalents of carboxylic groups of C, were prepared and characterized by DSC-TG, IR, and X-ray diffraction studies. Mechanistic studies with hydrophilic and hydrophobic basic drugs were conducted to explore the drug release patterns of SDPM. Besides, release and up-take studies were carried out in water and NaCl solution to examine the influence of ionic effects. The authors concluded that drugs can be loaded in a high proportion on to the polymer and therefore the resulting (C-D) material could be diluted with other polymers to modulate delivery properties of SDPM. Matrices of atenolol and lidocaine exhibited robust delivery properties with regard to change in proportion of loading D.

Acrylic Resins↗
PubMed2005

Dynamic swelling behavior of gamma-radiation induced polyelectrolyte poly(AAm-co-CA) hydrogels in urea solutions.

The aim of this study was to investigate the equilibrium swelling properties in urea solutions of gamma-radiation induced polyelectrolyte copolymeric hydrogels consisting of acrylamide (AAm) and crotonic acid (CA). Poly(acrylamide-co-crotonic acid), poly(AAm-co-CA) hydrogels containing different amounts of CA were obtained in the form of rods after radiation. Swelling experiments were performed in aqueous urea solutions at 25 degrees C, gravimetrically. The hydrogels showed large extents of swelling in aqueous (urea/water) media the swelling being highly dependent on the chemical composition of the hydrogels and irradiation dose. The percentage swelling of poly(AAm-co-CA) hydrogels was between 1160 and 4250%, while that of the AAm hydrogels was between 670 and 900%. The diffusional exponent values (n) are between 0.51 and 0.66, hence the diffusion of urea/water into the hydrogels is non-Fickian. Equilibrium urea/water contents of the hydrogel systems were changed between 0.870 and 0.977.

Acrylamides↗
PubMed2006

Swellable drug-polyelectrolyte matrices (SDPM) of alginic acid characterization and delivery properties.

This study deals with the development and characterization of the delivery properties of swellable drug-polyelectrolyte matrices (SDPM) of alginic acid (AA). Complexes (AA-D)(x) in solid state were obtained by neutralization of AA with different molar proportions (x) of model basic drugs (D), in which D is atenolol, metoclopramide and propranolol. They were characterized by DSC, IR and X-ray diffraction. Matrices prepared by compaction of (AA-D)(x) alone or in a mixture with sodium alginate (NaAA) were subjected to measurements of solvent up-take, release kinetics and erosion in three media (water, buffer of pH 6.8 and 0.01 M HCl). In addition, the dynamics of swelling was also evaluated. All SDPM assayed exhibited a remarkable zero order of delivery in water and buffer of pH 6.8 and also in two-step delivery experiments: 2 h in acid medium followed by a second step at pH 6.8. Experimental results indicate that the erosion of the hydrogel layer is the main delivery process. Delivery rate, can be modulated either by varying the composition of (AA-D)(x) or by diluting it with NaAA.

Alginates↗
PubMed2006

Formulation and cytotoxicity of doxorubicin loaded in self-assembled bio-polyelectrolyte microshells.

A bio-polyelectrolyte microshell composed of alginate sodium (ALG) and chitosan (CHI) was fabricated by electrostatic layer-by-layer (LbL) self-assembly technique. The resulting ALG-CHI microshells were found to be able to effectively load anti-cancer drug doxorubicin (DOX) in the interior of the shells under modest conditions without addition of other reagents, as demonstrated by confocal laser scanning microscopy (CLSM). The mass of DOX loaded in one capsule of four alginate/chitosan layers (i.e. the volume V=2.5x10(-10) cm3) is calculated as ca. 1.4x10(-13) g, which corresponds to 1.5x10(8) DOX molecules. Also, the release of DOX in the shells is dependent on the number of assembled layers of the shells. Colorimetric XTT cell viability assay results showed that the DOX-loaded microshells at high concentrations tested could kill cancer cells more efficiently than free-DOX alone.

Alginates↗
PubMed2004

Polyelectrolyte complexes as a tool for purification of plasmid DNA. Background and development.

The demand for highly purified plasmids in gene therapy and plasmid-based vaccines requires large-scale production of pharmaceutical-grade plasmid. Plasmid DNA was selectively precipitated from a clarified alkaline lysate using the polycation poly(N,N'-dimethyldiallylammonium) chloride which formed insoluble polyelectrolyte complex (PEC) with the plasmid DNA. Soluble PECs of DNA with polycations have earlier been used for cell transformation, but now the focus has been on insoluble PECs. Both DNA and RNA form stable PECs with synthetic polycations. However, it was possible to find a range of salt concentration where plasmid DNA was quantitatively precipitated whereas RNA remained in solution. The precipitated plasmid DNA was resolubilised at high salt concentration and the polycation was removed by gel-filtration.

Chromatography, Gel↗
PubMed2004

Solubilization of p-nitrophenol in aggregates formed by hydrophobically modified polyelectrolytes.

The solubilization of p-nitrophenol into the hydrophobic microdomains provided by polyelectrolytes carrying alkyl side chains of different length has been investigated in aqueous solutions of pH 5.0 and 8.0. Under these pH conditions p-nitrophenol is predominantly present in its neutral and ionic forms, respectively. Potassium salts of poly(maleic acid-co-1-olefins), PA-nK2 with n = 12, 14, 16, 18, were synthesized, and the pseudo-phase model was used to determine the distribution coefficient KS, and the standard free energy of transfer Deltamut0 of p-nitrophenol between water and polymer aggregates. The results indicate that at both pH's the solubilization of p-nitrophenol increases with increasing size of the side alkyl chain; i.e., the values of KS follow the order PA-18K2 > PA-16K2 > PA-14K2 > PA-12K2. The free energies, Deltamut0, were plotted as a function of the number of carbon atoms in the side alkyl chain and a linear relation was found. From these plots contributions of -0.324 and -0.676 kJ mol(-1) per methylene group were determined at pH 5.0 and 8.0, respectively. The effect of aggregate size on the solubility of phenol is attributed to the hydrophobic contribution per CH2 group to the free energy of transfer. The hydrophobic nature of the CH2 group is suggested to derive largely from the enthalpic contribution.

Journal Article↗
PubMed2004

Electrical properties of multilayers from low- and high-molecular-weight polyelectrolytes.

The formation of stable multilayer films by using as constituents sodium poly(4-styrene sulfonate) (PSS) and poly(4-vinyl pyridine) (PVP) was studied by electrooptics. A strong increase in basicity of the pyridine rings in the electrical field of the oppositely charged PSS chains was suggested to be the driving force for multilayer film formation. A linear increase in the film thickness was registered after deposition of the first three layers, with no dependence on the polyelectrolyte molecular weight. The electrooptical effect was found to increase with increasing area of each next layer, but depended on the molecular weights of both polymers. Polarization of "condensed" counterions along the chains of the last-adsorbed layer was suggested to explain this dependence. Following the counterion dynamics, we come to the conclusion that the electrical properties of the top layer govern the electrooptical behavior of the PSS/PVP film.

Electric Conductivity↗
PubMed2005

Salt softening of polyelectrolyte multilayer microcapsules.

By using a combination of atomic force and confocal microscopy, we explore the effect of 1:1 electrolyte (NaCl) on the stiffness of polyelectrolyte microcapsules. We study the "hollow" and "filled" (with polystyrene sulfonate) capsules. In both cases the shells are composed of layers of alternating polystyrene sulfonate (PSS) and polyallylamine hydrochloride (PAH). The stiffness of both "hollow" and "filled" capsules was found to be largest in water. It decreases with salt concentration up to approximately 3 mol/L and gets quasi-constant in more concentrated solutions. The "filled" capsules are always stiffer than "hollow." The observed softening correlates with the salt-induced changes in morphology of the multilayer shells detected with the scanning electron microscopy. It is likely that at concentrations below approximately 3 mol/L the multilayer shell is in a "tethered" state, so that the increase in salt concentration leads to a decrease in number of ionic cross-links and, as a result, in the stiffness. In contrast, above the critical concentration of approximately 3 mol/L multilayer shells might be in a new, "melted," state. Here the multilayer structure is still retained, but sufficient amount of ionic cross-links is broken, so that further increase in salt concentration does not change the capsule mechanics. These ideas are consistent with a moderate swelling of multilayers at concentrations below approximately 3 mol/L and significant decrease in their thickness in more concentrated solutions measured with surface plasmon spectroscopy.

Capsules↗
PubMed2005

Electrokinetic phenomena at grafted polyelectrolyte layers.

During the last decades the electrokinetic theory of Smoluchowski (Z. Phys. Chem. 92 (1918) 129) was extended to be applicable for soft surfaces (grafted polyelectrolyte layers (PL), biological and artificial membranes, etc.) by either using the Debye approximation or numerical solutions. In the theory of Ohshima (Colloids Surf. A 103 (1995) 249) the nonlinearized Poisson-Boltzmann (PB) equation for thick and uniform PL is solved analytically and a general hydrodynamic equation is derived in an integral form. These advantages in the theory of Ohshima provided a base for the further development of a generalized electrokinetic theory for soft surfaces. In his theory the final equation for the electroosmotic (electrophoretic) velocity is specified for the case of the complete dissociation of ionic sites within PL. Accordingly, the equation may be used only if the difference between pK and pH is very large. However, it turned out that an analytical solution of the nonlinearized PB equation for thick PL is possible for any degree of dissociation. This was achieved using the approximation of excluded coions if the absolute value of the reduced Donnan potential is larger than 2 and due to the simplification in the case of weak dissociation, when the absolute value of the reduced Donnan potential is less than 2. Combining this generalized double layer (DL) theory for PL and the theory of Ohshima enables to obtain an analytical equation for electroosmosis for the general case of any degree of dissociation. This equation creates for the first time a theoretical base for the interpretation of electrokinetic fingerprinting (EF) for the characterization of soft surfaces.

Algorithms↗
PubMed2005

Visco-elastic and adhesive properties of adsorbed polyelectrolyte multilayers determined in situ with QCM-D and AFM measurements.

The build-up of multilayers constructed from polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) under different pH conditions was continuously monitored using the quartz crystal microbalance with dissipation. The adsorbed amount of polymer as well as the amount of coupled water was determined. Furthermore, from dissipation measurements, it was possible to determine the visco-elastic properties of the adsorbed multilayer. These properties were highly dependent on the polyelectrolyte present in the outermost layer. The multilayer was far more rigid and elastic with PAA as the outermost layer. Furthermore, a link has been established between the conformability or rigidity of a multilayer covered surface and the adhesion between such surfaces. Adhesion measurements using the atomic force microscope showed a greater pull-off force when the more viscous PAH was present in the outermost layer.

Acrylic Resins↗