Polyelectrolyte Complex Films Research Articles

Characterization of a New Scaffold Formed of Polyelectrolyte Complexes Using Atomic Force and Ultrasonic Force Microscopy

Poly(acryloxyethyl-trimethylammonium chloride-co-2-hydroxyethyl methacrylate) [poly(Q-co-H)]/ sodium alginate gel (Ca2+) [AlgNa]/poly-l-lysine [PLL] films have been prepared on a mica surface. The structural arrangement and elasticity of the polyelectrolyte complexes have been studied with nanoscale resolution using Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). The elastic contrast on the AlgNa surface is indicative of the formation of a biopolymer network. On the AlgNa film, the surface morphology is mostly characterized by areas with rounded beads (approximately =150 nm in diameter) and polymer strands. Flatter, more homogenous surface regions are also present, presumably related to outdiffused PLL. Incorporation of the poly(Q-co-H) layer results in an increased compactness of the film, and an enhancement of the previous AlgNa topographic features. The unique subsurface sensitivity provided by UFM allows us to resolve the elastic bonding distribution in the buried biopolymer network by imaging from the poly(Q-co-H) overlayer. Provided the biocompatibility of the resulting polyelectrolyte complex film, we propose this system as a novel scaffold for bioengineering applications. The results we present demonstrate the potential of UFM to get insight in the elastic behavior of encapsulated bionetworks.

Controlled Molecular Organization of Surface Macromolecular Assemblies Based on Stimuli-Responsive Polypeptide Brushes

End-tethered cationic polypeptide brushes of poly(L-lysine) (t-PLL) were combined with three anionic polymers, poly(acrylic acid) (PAA), poly(L-glutamic acid) (PLGA), and poly(L-aspartic acid) (PLAA), to form reversible polyelectrolyte complex films at surfaces at neutral pH. The polyelectrolyte complex formation was confirmed by an in situ zeta-potential study and by positive fluorescent images after adding prelabeled anionic polymers. The secondary conformations of the t-PLL complex films depend upon the specific polyelectrolyte with which t-PLL was coupled as studied by circular dichroism and FTIR. Specifically, the random coil chain configuration of the t-PLL film was converted to an alpha-helical, beta-sheet, or random coil structure after forming complexes with PAA, PLGA, or PLAA, respectively. Each of these complexes could be returned to the original random coil t-PLL structure by a dilute acid rinse. Additional thickness and morphological studies from ellipsometry and atomic force microscopy have further shown that the corresponding film thicknesses of the individual solvated films were affected more by the secondary structures in films than by the adsorbed mass or surface net charges. The solvated thickness was reduced significantly after the random coil t-PLL film was coupled with polyanions in forming compact regulated structures in films. This biomimetic approach provides a new opportunity for controlling the molecular organization in surface macromolecular assemblies and may provide a model for structural study of protein complexes on a chip.

Characterization of silk fibroin/hyaluronic acid polyelectrolyte complex (PEC) films

This study aimed the characterization of the films casted from the aqueous mixtures of the pH induced complexes between silk fibroin (SF) and hyaluronic acid (HA). The insoluble and transparent films were subjected to scanning electron microscopy (SEM) analyses to show the morphological changes. Thermal analysis of complex films was determined by a differential scanning calorimeter (DSC). The changes in the crystalline state were monitored by X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). It was shown that the complexation between HA and SF was dominantly induced by pH. It was shown that the complex films comprised mixtures of crystalline and non-crystalline regions.

Hydration Contributions to Association in Polyelectrolyte Multilayers and Complexes: Visualizing Hydrophobicity

Thin films of polyelectrolyte complex were assembled using the multilayering method with direct, in situ observation of all multilayer components using attenuated total internal reflectance FTIR (ATR-FTIR). Buildup and ion doping of two representative combinations of positive and negative polyelectrolytes are controlled by salt type. The internal hydration of multilayers, measured precisely by ATR-FTIR, depends on the chemical identities of the polymers and the salt ions. The efficiency of doping inversely tracks the degree of hydration: less hydrated ("hydrophobic") ions are more efficient dopants, and less hydrated polyelectrolye complexes are harder to dope. Given that polyelectrolyte complexation is essentially entropy-driven, driving forces for doping, or association (the inverse of doping), are rationalized by counting all species in the condensed polyelectrolyte phase, including water molecules. For any combination of uni-univalent salt ions and polyelectrolyte, the strength of polyelectrolyte association is described by a single universal parameter. The magnitudes of the interactions per repeat unit are not high--a few kT--and are proportional to the number of water molecules released from the polymers when they form ion pairs. Hydration within multilayers due to residual salt is extensive but may be removed by an external osmotic stressing agent.

Preparation and characterization of free mixed-film of pectin/chitosan/Eudragit ® RS intended for sigmoidal drug delivery

Polyelectrolyte complex (PEC) film between pectin as an anionic polyelectrolyte and chitosan as a cationic species was prepared by blending two polymer solutions at weight ratio of 2:1 and then solvent casting method. Besides pectin/chitosan PEC film, Eudragit ® RS, pectin/Eudragit ® RS and pectin/chitosan/Eudragit ® RS films were also prepared by aforementioned method. In mixed-film formulations, a fixed weight ratio of 1:5 of pectin or pectin/chitosan complex to Eudragit ® RS was used. Characterizations of pectin/chitosan interaction in solution were investigated by turbidity and viscosity measurement and in the solid state by Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXRD) and thermogravimetric analysis (TGA). It was observed that the swelling profile of pectin/chitosan film was pH-dependent and its swelling ratio in phosphate buffer solution (PBS) pH 7.4 was about 2.5-fold higher than that of PBS pH 6.0. Formulation containing only pectin/chitosan could not protect free film from high swelling in the aqueous media, therefore, Eudragit ® RS as a water-insoluble polymer must be included in the mixed-film. The formation of PEC between pectin and chitosan resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. Drug permeation or diffusion studies were carried out using Plexiglas diffusion cell consisting of donor and acceptor compartments. Theophylline was selected as a model drug to measure permeability coefficient. Drug permeation through pectin/chitosan/Eudragit ® RS showed a sigmoidal pattern; whereas drug diffusion through pectin/Eudragit ® RS and Eudragit ® RS films followed a linear characteristic. The drug permeation through the ternary mixed-film showed a burst release upon exposure to PBS pH 6.0. This mixed-film formulation showed the potential for sigmoidal drug delivery with an initial, controllable slow release followed by a burst release immediately after the change in pH. The burst drug permeation might possibly be due to change in film’s porosity.

Carboxymethyl Cellulose:Polyvinylamine Complex Hydrogel Swelling

The swelling behavior of the polyelectrolyte complex films made from polyvinylamine (PVAm) or poly(vinylformamide-co-vinylamine) copolymers and carboxymethyl cellulose (CMC) was studied as a function of polymer composition, pH, and salt concentration. Swelling is determined by the balance between ionic cross-link density, opposing swelling, with solvation and Donnan effects promoting swelling. Films containing excess ammonium groups gave the greatest swelling at low pH, whereas excess carboxyl groups enhanced swelling at high pH. Films with balanced charge stoichiometry (CMC:PVAm 3:1 w:w) gave the minimum swelling. High concentrations of sodium chloride increased swelling due to the decomposition (screening) of ionic cross-links, whereas calcium ion decreased swelling possibly because of calcium dicarboxylate cross-links. A simple swelling model based on the ionization behavior of dilute polymers and ionic cross-linking predicted the major swelling behaviors, including the effects of pH and polymer compos...

Mechanical Properties of Polyelectrolyte Complex Films Based on Polyvinylamine and Carboxymethyl Cellulose

Homogeneous polyelectrolyte complex films were cast from mixtures of poly(vinylamine-co-vinylformamide) and carboxymethyl cellulose (CMC) in 50% formic acid aqueous solution with compositions varying between CMC blended with pure polyvinylamine (PVAm) and CMC blended with pure poly(N-vinylformamide) (PNVF). The tensile strength and tensile modulus of the complex films were measured as functions of polymer ratio, molecular weight, function group content, and water content. PVAm addition lowered the strength and modulus of dry CMC whereas PNVF did not; intermediate PVAm−PNVF copolymers gave intermediate results. Mechanical strength decreased with increasing molecular weight of CMC and carboxyl content, but was not affected by molecular weight of PVAm. The mechanical properties of all the films decreased with increasing water content. CMC:PVAm films were swollen gels in water, whereas CMC:PNVF films dissolved in water. Heating did not improve the mechanical strength, whereas cross-linking with 5% glutaraldeh...

Effects of mixing ratio on the mechanical and thermal properties of polyelectrolyte complex film

Polyelectrolyte complex films were prepared with two compounds, chitosan and poly(ethylene glycol)-monosuccinate, using a casting in order to synthesize a polyelectrolyte complex film with various mole ratios of chitosan and poly(ethylene glycol)-monosuccinate. The solution properties of isolated PEC were investigated for the effects of FTIR, pH value, Brookfield viscosity and cell viability assay using MTT staining. The PEC films were evaluated for mechanical properties by typical stress-strain curve, for thermal properties by DSC and TGA and for surface morphology properties by SEM. Furthermore, the surface resistance, moisture regain and water content of the films were characterized. The solution properties were affected by several factors including the chitosan content in the PEC, the mixing ratio of PEG and chitosan, and pH. Several PEC in acidic conditions exhibited film formation under appropriate conditions of mixing ratio and chitosan concentration in the mixing process. These PEC films were found to have sufficiently flexible and stable properties due to their hydrophilic structure, which was formed by the oppositely charged interaction between PEG-MS and chitosan matrix. The results showed the potential applicability of chitosan and poly(ethylene glycol)-monosuccinate films as a biocompatible polymer.

The response of normal human osteoblasts to anionic polysaccharide polyelectrolyte complexes

Polyelectrolyte complexes (PEC) were prepared from chitosan as the polycation and several synthesized functional anion polysaccharides, and their effects on cell attachment, morphology, proliferation and differentiation were estimated using normal human osteoblasts (NHOst). After a 1-week incubation, PEC made from polysaccharides having carboxyl groups as polyanions showed low viability of NHOst on it although the NHOst on it showed an enhancement in their differentiation level. On the other hand, NHOst on PEC made from sulfated or phosphated polysaccharides showed similar attachment and morphology to those on the collagen-coated dish. When the number of NHOst was estimated after 1 week, the number on the PEC was ranged from 70% to 130% of those on the collagen-coated dish, indicating few effects of these PEC on cell proliferation. In addition, NHOst on PEC films made from sulfated polysaccharides differentiated to a level very similar to that observed on the collagen-coated dish, indicating that these PEC films maintain the normal potential of NHOst to both proliferate and differentiate. Measurement of gap junctional intercellular communication of NHOst on PEC revealed that PEC did not inhibit communication, suggesting that PEC films have few effects on cell homeostasis. Thus, PEC made from the sulfated polysaccharide may be a useful material as a new scaffold for bone regeneration.

Self-assembly and characterization of polyelectrolyte complex films of hyaluronic acid/chitosan

Due to the theoretical and practical importance of hyaluronic acid (HA) and chitosan in biomedical engineering, self-assembly polyelectrolyte complex films of HA/chitosan were fabricated with two different strategies and characterized by atomic force microscopy (AFM). With the first strategy, while the mica was rich in negative charges, chitosan was fabricated first and the HA were fabricated secondly. The films exhibited cluster features on the substrate. With the second strategy, while the mica was modified to be in positive charges, HA was fabricated first and chitosan was fabricated secondly. The films exhibited a more homogeneous feature and a nice miscibility at nanometer scale and had a lower roughness than pure chitosan films. The self-assembly polyelectrolyte complex films by strategy two were smoother and more uniform than the ones by strategy one.

PH- and temperature-sensitive release behaviors from polyelectrolyte complex films composed of chitosan and PAOMA copolymer

This paper describes the pH and temperature effects on drug release from polyelectrolyte complex (PEC) films composed of a cationic polymer, chitosan, and an anionic polymer, polyalkyleneoxide–maleic acid copolymer (PAOMA). In this study, we prepared and investigated PEC films in terms of the drug release properties as pH- and temperature-sensitive drug carriers. Drug release rates were tested at pH 3.8 and 7.2, and at 25 and 50 °C. Salicylic acid and phenol were selected as model drugs. An increase in pH from 3.8 to 7.2 resulted in an increase in the rate of drug release because of the repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs. When the hydrophobic PAOMA was used as a polyanion, the drug release rate increased at 50 °C. This is attributed to the increase of release area due to the phase transition of PAOMA and the increase of repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs.

PH- and temperature-sensitive permeation through polyelectrolyte complex films composed of chitosan and polyalkyleneoxide–maleic acid copolymer

The pH- and temperature-effects on drug permeation from polyelectrolyte complex (PEC) films composed of a cationic polymer, chitosan (CS) and an anionic polymer, polyalkyleneoxide–maleic acid copolymer (PAOMA), have been investigated. In this study, we prepared and investigated PEC films for utility as on–off switches in drug transport. PEC films were prepared by a casting/solvent evaporation method. PEC films swelled at low pH and low temperature. This swelling behavior was reversible with the films responding rapidly to a change in environmental pH and temperature. Drug permeation rates were tested with pH 3.8 and 6.2 at 25 and 50 °C. Salicylic acid, phenol and glucose were selected as model drugs to examine the effect of molecular weight. A decrease in pH from 6.2 to 3.8 and an increase in temperature from 25 to 50 °C resulted in a corresponding increase in the rate of drug permeation. Of the three model drugs tested, glucose, with the highest molecular weight showed the lowest effective diffusion coefficient.

Polyelectrolyte complex films derived from polyethyleneoxide-maleic acid copolymer and chitosan: preparation and characterization.

Polyelectrolyte complex films were prepared with polyethyleneoxide-maleic acid copolymer and chitosan using a casting/solvent evaporation method. The films were examined in terms of their IR spectra, surface and cross-section morphologies, cytotoxicity, and swelling behavior at different pH levels. To assess the potential of these films as a biomedical device, the profiles of the release of model drug from the CS/PEOMA films were examined at pH 4.8. The surface morphology of the films was quite smooth and uniform, and the cross-sectional morphology was dense and homogeneous. The swelling behaviors of CS/PEOMA films were found to depend on the pH of the solution as well as on the CS/PEOMA composition. Drug release from different CS/PEOMA films at pH 4.8 was found to be dependent on film composition. The results showed the potential applicability of CS/PEOMA film as a drug delivery vehicle.

PH-Gated Permeability of Variably Charged Species through Polyelectrolyte Multilayer Membranes

The transport of weak acid/base molecules through ultrathin films of polyelectrolyte complex formed by the multilayering method was measured by electrochemical means. The net flux of probe molecule through multilayers is a linear combination of all forms in which that probe is found. Neutral molecules are able to traverse the membrane faster because they rely on nonspecific hopping, whereas charged molecules require extrinsically charged sites, which are doped into the multilayer by external salt. Control over probe charge by external pH is thus an effective way to influence net membrane transport. Flux was simulated by Monte Carlo methods and by analytical expressions, which showed that the pH-dependent component of flux was essentially mirrored by the solution titration curve of the weak acid. In situ attenuated total internal reflection Fourier transform IR measurements revealed that multilayer probe concentration was independent of both the solution salt concentration and state of ionization.

Optically active polyelectrolyte multilayers as membranes for chiral separations.

Ultrathin films of chiral polyelectrolyte complex, prepared by the multilayering process, exhibit selectivity in the membrane separations of optically active compounds, such as l- and d-ascorbic acid. The flux through these polyelectrolyte multilayers, PEMUs, is exceptionally high and may be controlled by the concentration of salt present in the permeating solutions. Both in-situ ATR-FTIR and chiral capillary electrochromatography indicate that flux selectivity is mainly kinetically controlled, stemming from a difference in diffusion rates of various enantiomers through PEMUs, rather than a difference in partitioning.

Thermal Characteristics of Polyelectrolyte Complexes Composed of Chitosan and Hyaluronic Acid

The thermal characterization of the polyelectrolyte complexes (PEC) was investigated by thermogravimetric analysis (TGA) and dielectric analysis (DEA). In the results of the DEA, two relaxation peaks appeared around 50 and 180°C in the sample, CSHA11. The relaxation peak of all samples increased the temperature because of an increase in the number of chitosan segments in the PEC films. The activation energy of the relaxation process was obtained by performing a linear least squares analysis (Arrhenius plot) on the plot of ln(frequency) vs. 1/T max, where T max is the temperature which corresponds to the loss factor peak maximum at various test frequencies using the Arrhenius equation. The thermal decomposition and thermal stability of hyaluronic acid (HA), chitosan, and PEC films were investigated using TGA.

ポリイオンコンプレックスを用いたプロトン伝導膜の作製とそのイオン伝導特性

We have developed a novel proton-conduction film by recasting an aqueous solution comprising an acid polymer and a base polymer. This technique is called the polyelectrolyte complex method, in which a film is generally formed by using a concentrated acidic solution, because it is hard to obtain a stable one from a neutral solution. First, poly (sodium-p-stylenesulfonate) (PSSNa) was partially changed to a proton form (PSS) by using cation exchange polymer beads prior to the blending with polyethyleneimine (PEI). By using thus-prepared neutral aqueous blend solution, it has been possible to prepare a stable polyelectrolyte complex film that demonstrates a higher ionic conductivity than that of Nafion. This report also describes ionic conductivity dependence on a SS/EI mole ratio and acid-activation processes of the film.

A novel approach to prepare tripolyphosphate/chitosan complex beads for controlled release drug delivery

A novel approach was developed to improve the mechanical strength of tripolyphosphate (TPP)/chitosan beads prepared under coagulation condition at 4°C in the presence of gelatin. Cross-sectional analysis indicated that the beads had a homogeneous crosslinked structure, as a result the beads were strengthened greatly (the mechanical strength increased more than ten times). Furthermore sodium alginate (a polyanion) can interact with cationic chitosan on the surface of these TPP/chitosan beads to form polyelectrolyte complex film for the improvement of the drug sustained release performances. The loading efficiency of model drugs (brilliant blue and FITC-dextran) in these beads was very high (more than 90%). Crosslinking time, TPP solution pH and other preparation factors had an effect on the drug release performance of beads. The release period of brilliant blue (a poor water soluble dye) was more than 2-months at a fairly constant rate in 0.9% NaCl, 10 mM PBS pH 7.4. However, for FITC-dextran (a water soluble polysaccharide) only 1–2 days in the same conditions. It seems that TPP/chitosan bead prepared by the novel method is a promising formulation for drug delivery.

PEC films prepared from Chitosan-Alginate coacervates.

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.

Properties of polyelectrolyte complex films of chitosan and gelatin

Properties of polyelectrolyte complex films of chitosan and gelatin