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PubMed2006

Photooxidative degradation of dye pollutants accumulated in self-assembled natural polyelectrolyte microshells under visible radiation.

A novel route to facilitate the degradation of dye pollutants, a class of well-known recalcitrant organic pollutants, is reported. This new approach is based on a natural polyelectrolyte microshell that was preformed by the alternate adsorption of the anionic alginate sodium (ALG) and the cationic chitosan (CHI) onto weakly cross-linked melamine formaldehyde (MF) colloidal particles, and the subsequent sacrifice of MF templates in 0.1 M HCl. The as-prepared microshells could accumulate rhodamine B (RhB) and fluorescein (Flu) efficiently in water under ordinary conditions by means of a simple mixing process. The photodegradation of the accumulated RhB and Flu was examined in the presence of Fe3+ and H2O2 under visible radiation. The accumulated RhB and Flu are rapidly degraded and the assembled shells maintain their intact spherical shape throughout the photoreaction process. Results of recycling degradation experiments and the photochemical behavior of the shells, as demonstrated by confocal laser scanning microscopy (CLSM), UV-visible spectroscopy, and scanning force microscopy (SFM), further suggest that the constructed shells may be used as environmentally friendly microcontainers for the elimination of dyes in wastewater.

Journal Article↗
PubMed2006

Freestanding polyelectrolyte films as sensors for osmotic pressure.

Freestanding ultrathin polyelectrolyte-multilayer membranes, transferred to topographically structured polydimethylsiloxane (PDMS), are used as mechanical sensors. Due to the membranes' semipermeability, high-molecular-weight molecules can be either entrapped inside them or excluded, thus generating an osmotic pressure. This leads to a deformation. We investigate the deformation as a function of the osmotic pressure and present an analytical theory that fully describes the data. Thus, osmotic pressures can be determined quantitatively. The individual osmotic-sensitive elements have only microscopic dimensions, and arrays can be easily produced.

Chemistry, Physical↗
PubMed1997

Size-based separation of polyelectrolytes by capillary zone electrophoresis: migration regimes and selectivity of poly(styrenesulphonates) in solutions of derivatized cellulose.

The migration regimes and the separation selectivity of linear poly(styrenesulfonates) (PSS) were investigated in solutions of linear polymeric hydroxyethylcellulose (HEC). Variable parameters were the number of PSS monomer units (in the range of 25-6520), HEC concentration (below and above the entanglement threshold), molecular mass of HEC (between 35900 and 438000 Da) and electric field strength (from 190 to 1140 V/cm). Besides those regimes which are known for migration of polyelectrolytes in physical networks (Ogston sieving, reptation without and with orientation), the observed separation below the entanglement threshold indicates an effect of solute-chain interactions similar to that observed for the separation of double-stranded DNA. From the dependence of the separation selectivity on HEC concentration and molecular weight it was found that both parameters increase the separation. The selectivity of the solutions of higher concentrated low molecular HEC was compared to lower concentrated high molecular HEC, which has a similar bulk viscosity, and therefore obeys comparable peak dispersion due to thermal broadening. At high field strengths (preferably used in capillary electrophoresis) the former gave better separation only for shorter PSS molecules. For separation of longer PSS molecules, only high molecular HEC is applicable due to the deformation of the low molecular matrix by large analyte molecules.

Cellulose↗
PubMed2006

Characterization of the SDS-induced electroosmotic flow in micellar electrokinetic chromatography with cationic polyelectrolyte-coated capillaries.

Manipulation of the EOF is essential for achieving optimal separations by MEKC. In this paper, we present an extensive investigation of the effect of common experimental conditions on the EOF observed in a capillary coated with poly(diallyldimethylammonium chloride) (PDADMA) polyelectrolyte under MEKC conditions. It was found that highly reproducible cathodal EOF is achieved approximately at or just below the conditional CMC value of SDS in the electrolytes used. At concentrations of SDS greater than the CMC the EOF is independent of pH. The impact of common organic modifiers (ACN, methanol, urea, beta-CD and nonionic surfactant) on the EOF behavior in both a PDADMA-coated capillary and a bare silica capillary is compared. The suppressing effect of organic modifiers on the EOF is much stronger for coated capillary indicating that these compounds additionally reduce the negative charge density on the capillary surface due to alteration of the surfactant coating.

Cations↗
PubMed1987

Application of polyelectrolytes to fractionation of alfalfa juice protein (short communication).

The quantities of protein which can be extracted from green plants depend on a number of factors such as the botanical composition of the plant, its growth stage, topdressing and system of extraction. Leaf protein concentrates have been incorporated into food for human consumption, but their green color has limited its application. Thermal precipitation of chloroplastic material is not specific, causes denaturation and requires high energy input. A selective recovery of the green fraction is possible by centrifugation at high centrifugal forces or by the combination of this method with an addition of calcium salt to a green juice. Application of high molecular polyelectrolytes in green juice precipitation allows the separation of pigmented material at room temperature. The objective of this work was to determine the effect of cationic and anionic flocculants on fractionation of alfalfa green juice into two fractions: chloroplastic (green LPC) and cytoplasmatic (white LPC).

Chemical Fractionation↗
PubMed1983

Degradative analysis of glass ionomer polyelectrolyte cements.

As part of a detailed investigation of the setting mechanisms of dental polyelectrolyte cements, the Al3+, Ca2+, and Na+ concentrations in the matrix phase of glass ionomer cements were measured as a function of the cements age by use of a selective degradation technique. In the early stages of cement formation, all three cations were rapidly released from the glass, and it is inferred that both Ca2+ and Al3+ are responsible for gelation. Even after 5 X 10(4) min, the reaction was incomplete and still continuing.

Aluminum↗
PubMed2004

Lubrication and wear properties of grafted polyelectrolytes, hyaluronan and hylan, measured in the surface forces apparatus.

Hyaluronan is believed to have an important function in the boundary biolubrication of articular cartilage. Using a Surface Forces Apparatus, we tested the tribological properties of surface bound, rather than "free" hyaluronan. The grafting process of the polyelectrolyte included either a biological route via an HA-binding protein or a chemical reaction to covalently bind the polymer to a lipid bilayer coated surface. In another reaction, we constructed a surface with covalently grafted hylan (crosslinked hyaluronan). We studied the normal and shear forces between these surfaces. None of the systems demonstrated comparable lubrication to that found between cartilage surfaces except at very low loads. Both grafted hyaluronan and hylan generated coefficients of friction between 0.15 and 0.3. Thus, the polysaccharide, which is a constituent of the lamina splendens (outermost cartilage layer), is not expected to be the responsible molecule for the great lubricity of cartilage; however, it may contribute to the load bearing and wear protection of these surfaces. This was concluded from the results with hylan, where a thin gel layer was sufficient to shield the underlying surfaces from damage even at applied pressures of over 200 atmospheres during shear. Our study shows that a low coefficient of friction is not a requirement for, or necessarily a measure of, wear protection.

Aluminum Silicates↗
PubMed2006

In vitro antibacterial and cytotoxicity assay of multilayered polyelectrolyte-functionalized stainless steel.

Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic and implant surgery. In the present study, a new strategy for confering stainless steel with antibacterial property via the alternate deposition of quaternized polyethylenimine (PEI) or quaternized polyethylenimine-silver complex and poly(acrylic acid) (PAA) was investigated. The success of the deposition of the polyelectrolyte multilayers (PEM) and its chemical nature was investigated by static water contact angle and X-ray photoelectron spectroscopy (XPS), respectively. The antibacterial activity was assessed using Escherichia coli (E. coli, a gram-negative bacterium) and Staphylococcus aureus (S. aureus, a gram-positive bacterium). The inhibition of E. coli and S aureus growth on the surface of functionalized films was clearly shown using the LIVE/DEAD Baclight bacterial viability kits and fluorescence microscopy. The cytotoxicity of the PEM to mammalian cells, evaluated by the MTT assay, was shown to be minimal and long-term antibacterial efficacy can be maintained. These results indicate new possibilities for the use of such easily built and functionalized architectures for the functionalization of surfaces of implanted medical devices.

Anti-Bacterial Agents↗
PubMed2007

Layer-by-layer assembly of polyelectrolyte films improving cytocompatibility to neural cells.

The using of layer-by-layer assembly polyelectrolyte (PE) films has been suggested as a new versatile technique for surface modification aimed at tissue engineering and cell-based chips. In this study, we investigated the surface morphology of the hyaluronic acid (HA)-based PE films deposited on the amino-functionalized glass slides using atomic force microscopy. These thin films (bilayer number <9) were measured to have nanoscale roughness ranging from 10 to 100 nm. Then the primary hippocampal and cortical neural cells were cultured on the PE films, respectively. After 5 days of culturing, the cytocompatibility to neural cells was evaluated by cellular morphology, neurite outgrowth, and microtubule-associated protein 2 expressions. From the present results, the HA-based PE films were found to be able to support neural cell adhesion and neurite development, especially for the polycation-ending films. It is suggested these HA-based multilayer PE films or similar build-ups could thus be used in the future as a way to modify surfaces for nerve scaffolds and neuron-based chips.

Animals↗
PubMed2005

Novel polyelectrolyte carboxymethyl konjac glucomannan-chitosan nanoparticles for drug delivery. II. Release of albumin in vitro.

Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles were spontaneously prepared under very mild conditions via polyelectrolyte complexation. Bovine serum albumin (BSA), as a model protein drug, was incorporated into the CKGM-CS nanoparticles. The physicochemical properties of the BSA-loaded nanoparticles were identified by Zetasizer 3000 and FTIR spectrophotometry. Their sizes were from 330 nm to 900 nm; zeta potentials were positive according to varies CKGM/CS ratios. The encapsulation efficiency was up 20%. The release behavior in vitro of BSA from the nanoparticles was also investigated. We could find that the BSA release from the CKGM-CS nanoparticles is much more influenced by the CS coating layer than by the CKGM inner structure. And the CKGM-CS matrices not only exhibited pH-responsive properties, but ionic strength-sensitive properties. These systems may present a potential for pulsatile protein drug delivery.

Delayed-Action Preparations↗
PubMed2002

Confocal laser scanning microscopy to study formation and properties of polyelectrolyte nanocapsules derived from CdCO3 templates.

Three-dimensional confocal laser scanning microscopy (CLSM) was used as an essential investigation method to obtain information about the formation and morphological characteristics of nanocapsules. Nanocapsules are built by layer-by-layer deposition of alternatively charged polyelectrolytes on templates forming nanostructured hollow shells. CLSM is unique in allowing for monitoring of the core dissolution process in real time and for studying nanocapsule functioning in hydrated conditions within a three-dimensional and temporal framework. Since we are also interested in the identification of other possible templates, we briefly report on the use of yeast cells as biocolloidal cores monitored by means of two-photon microscopy. Here we focus our attention on the use of CdCO(3) crystals as template candidates for the preparation of stable capsules. Both cubic and spherical CdCO(3) cores have been produced. Cubic cores exhibit higher monodispersity and smaller size compared to spherical ones. Capsules templated on these cores have a higher surface-to-volume ratio that is valuable for applications related to drug delivery, functional properties of the shells and adsorption of proteins, and other biologically relevant molecules. Microsc. Res. Tech. 59:536-541, 2002.

Journal Article↗
PubMed2005

Capillary electrochromatography using polyelectrolyte multilayer coatings.

This review covers recent progress in polyelectrolyte multilayer (PEM) coatings applied to analytical separations using open-tubular capillary electrochromatography (OT-CEC). The simple preparation procedure involved in the PEM approach has provided some attractive features over other modes of capillary electrophoresis-based separations including packed column capillary electrochromatography (PC-CEC) and micellar electrokinetic chromatography (MEKC). PEM coatings have been used to alleviate the adsorption of basic analytes, to improve separations, and to improve the stability of the electroosmotic flow. Fundamental aspects of PEM coatings on surfaces and analytical separation platforms are briefly outlined in this review. In addition, applications of PEM coatings to fused-silica capillaries or microchip separation devices for the separation of small achiral or chiral analytes, as well as large biomolecules, are discussed.

Journal Article↗
PubMed2004

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.

Absorption↗
PubMed2006

Chemo-enzymatic synthesis of raffinose-branched polyelectrolytes and self-assembly application in microcapsules.

A novel biocompatible polyelectrolyte poly(vinyl raffinose-co-acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe(2+)/K(2)S(2)O(8)/H(2)O(2) starting from enzymatically-synthesized monomer: 1-O-vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV-Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano-capsule-carrying galactose residue is a potential targeting drug-controlled delivery systems.

Acrylates↗
PubMed2006

Monomodal polyelectrolyte complex nanoparticles of PDADMAC/Poly(styrenesulfonate): preparation and protein interaction.

The binding of the model proteins HSA, LYZ and MYO to PEC nanoparticles is reported. PEC particles were prepared by mixing solutions of PDADMAC either with PSS or PMA-MS, followed by consecutive centrifugation. Monomodal anionic (PEC-1.50) and cationic (PEC-0.66) PEC particles were obtained using non-stoichiometric mixing ratios. PEC/protein conjugates were prepared by adding charged protein solutions to dispersions of respective like charged PEC particles, followed by one centrifugation step. Mixing proteins and PEC particles under attractive conditions led to flocculation of the dispersion. From CD, DLS and AFM the following trend for protein binding at PEC particles under repulsive conditions was obtained: HSA/PEC-1.50 > MYO/PEC-1.50 > LYZ/PEC-0.66. Protein uptakes up to 0.33 g x g(-1) (protein/PEC) (CD) and particle diameter enlargements up to 13 nm (AFM) were obtained at c(PROT) = 0.091 mg . mL(-1). Furthermore, novel spin coated films of PEC particles were interacted with proteins under both repulsive and attractive conditions. In-situ ATR FT-IR spectroscopy revealed that the adsorbed amount of HSA and LYZ under attractive conditions was significantly higher than under repulsive ones, which is analogous to protein adsorption at polyelectrolyte multilayers terminated either by polycation or polyanion. Similarly to the dispersed PEC/protein conjugates, under repulsive conditions the uptake of HSA was higher compared to LYZ. The shown protein uptake under repulsive conditions is related to concepts of mild enzyme or protein binding at nonbiogenic substrates.

Circular Dichroism↗
PubMed2000

Production of Fab fragments of monoclonal antibodies using polyelectrolyte complexes.

A new method for the production of monovalent Fab fragments of antibodies has been developed. Traditionally Fab fragments are produced by proteolytic digestion of antibodies in solution followed by isolation of Fab fragments. In the case of monoclonal antibodies against inactivated subunits of glyceraldehyde-3-phosphate dehydrogenase, digestion with papain resulted in significant damage of the binding sites of the Fab fragments. Antigen was covalently attached to the polycation, poly(N-ethyl-4-vinylpyridinium bromide). Proteolysis of monoclonal antibodies in the presence of the antigen-polycation conjugate followed by (i) precipitation induced by addition of polyanion, poly(methacrylic) acid, and pH shift from 7.3 to 6.5 and (ii) elution at pH 3.0 resulted in 90% immunologically competent Fab fragments. Moreover, the papain concentration required for proteolysis was 10 times less in the case of antibodies bound to the antigen-polycation conjugate than that of free antibodies in solution. The digestion of antibodies bound to the antigen-polyelectrolyte complex was less damaging, suggesting that binding to the antigen-polycation conjugate not only protected binding sites of monoclonal antibodies from proteolytic damage but also facilitated the proteolysis probably by exposing antibody molecules in a way convenient for proteolytic attack by papain.

Animals↗
PubMed1997

Cryo-TEM of Polyelectrolyte-Micelle Complexes

Cryo-TEM was carried out on samples containing polyelectrolyte-micelle complexes, formed by combining poly(diallyldimethylammonium chloride) (PDADMAC), a strong cationic polyelectrolye, with oppositely charged mixed micelles of sodium dodecyl sulfate (SDS) and nonionic Triton X-100 (TX100), in 0.40 M NaCl. Complexation appears to involve the formation of micelle-rich regions, presumably within the domains of polymer chains, without any particular organization or restructuring of the micelles. At polymer concentrations (CP) </= 0.4 g/L, the observation of such clusters with dimensions as low as 50 nm suggests that intrapolymer complexes may exist at low CP. With increasing polymer concentration, aggregates grow in size, with dimensions that indicate the involvement of many polymer chains. Upon increase in the ratio of SDS:TX100, the system coacervates, and the micelle/polymer-rich phase forms a continuous matrix.

Journal Article↗
PubMed1997

Electrophoretic Mobility of a Polyelectrolyte-Adsorbed Particle: Effect of Segment Density Distribution

Varoqui's theory [Nouv. J. Chim. 6, 187 (1982)] for the electrophoretic mobility of a charged colloidal particle adsorbed by neutral polymers with an exponential distribution of the polymer segments is extended to the case where adsorbed polymers are charged. An analytic mobility expression is derived on the basis of the linearized Poisson-Boltzmann equation. Comparison is made with the case of particles coated with a polyelectrolyte layer of fixed thickness with uniform segment distribution.

Journal Article↗