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PubMed2003

Elastic properties of polyelectrolyte capsules studied by atomic-force microscopy and RICM.

Mechanical properties of polyelectrolyte multilayer capsules were studied using a new method combining atomic-force microscopy and reflection interference contrast microscopy. By measuring the force vs. deformation for poly(styrene sulfonate)/poly(allylamine) capsules the existence of different deformation regimes depending on the applied deformation was shown. The present paper focuses on the small-deformation regime. The elastic response of the deformed capsule was studied as a function of the wall thickness and the capsule size, and showed the theoretically expected variations. The Young modulus obtained from the experiments ranges between 1.3 and 1.9 GPa.

Capsules↗
PubMed2005

In vivo tumor targeting of ODN-PEG-folic acid/PEI polyelectrolyte complex micelles.

A tumor-targeting antisense oligodeoxynucleotide (ODN) delivery system based on polyelectrolyte complex (PEC) micelles is demonstrated. ODN-PEG-folic acid (ODN-PEG-FA) was synthesized using a heterofunctional PEG linker. The PEC micelles for the targeted ODN delivery to tumor cells were produced by ionic interactions between the ODN-PEG-FA and polyethylenimine (PEI). The in vivo targeting properties of the PEC micelles were assessed using a mouse tumor model. The size of ODN-PEG-FA/PEI PEC micelles was 92.3 nm with a relatively narrow distribution. Cellular uptake of the ODN-PEG-FA/PEI PEC micelles by folic acid receptor over-expressing cells (KB) was greatly enhanced compared to that of ODN-PEG/PEI PEC micelles. When the ODN-PEG-FA/PEI PEC micelles were systemically administered to the mice bearing KB cell xenograft tumor, ODN was accumulated to the solid tumor in a target specific manner. This study suggests that the PEC micelles with a receptor-recognizable targeting ligand on the surface have potential for passive and active targeted delivery of ODN drugs to cancer cells.

Animals↗
PubMed1998

Effect of polyelectrolyte complex (PEC) on human periodontal ligament fibroblast (HPLF) functions in the presence of glucocorticoids.

Cell functions in vivo are stimulated by extracellular matrices, vitamins, growth factors, and hormones. In this paper, the effects of glucocorticoids, dexamethasone (Dex), and Cortexrone (Cor) on the growth and differentiation of human periodontal ligament fibroblast (HPLF) were discussed in relation to a polyelectrolyte complex (PEC) consisting of polysaccharides (chitin, cellulose derivatives, and chitosan) as a tissue-culture material. A Dex-treatment at a concentration of 10(-)-10(-7) M inhibited one-half of HPLF growth in comparison with 10(-9) M Dex-treatment and no additive medium and produced aggregates on the chitosan-sulfated chitin PEC (SPECs) with regard to the degree of sulfate substitution. On the chitosan-sulfated cellulose PEC, 10(-7)-10(-9) M Dex-treatment promoted HPLF growth and inhibited the production of aggregates. On the other hand, a Cor-treatment, a mineral corticoid, which inhibits the interaction between Dex and its receptor, increased HPLF growth on SPEC141, but the HPLF did not construct aggregates. A Dex and Cor mixture-treatment inhibited one-third HPLF growth in comparison with 10(-5) M Dex-treatment and produced aggregates on PEC. The cooperative effect of both the culture material and hormones was found to control HPLF growth and morphology. The alkaline phosphatase (ALPase) activities of HPLF increased with an increase in the Dex and Cor concentration. The value of Dex-treated HPLF ALPase activity demonstrated a two-fold increase from that with Cor-treatment. The ALPase activity of Dex and Cor mixture-treated HPLF on PEC decreased with an increase in the Cor concentration, because Cor increased HPLF growth on PEC. In using carboxymethylated chitin derivatives as the polyanion, HPLF decreased in cell growth and produced aggregates in the absence of the additives, suggesting that PEC induces HPLF differentiation using only the stimulation of the material surface.

Alkaline Phosphatase↗
PubMed2004

Polyelectrolyte-mediated assembly of copper-phthalocyanine tetrasulfonate multilayers and the subsequent production of nanoparticulate copper oxide thin films.

An approach to producing films of nanometer-sized copper oxide particulates, based on polyelectrolyte-mediated assembly of the precursor, copper(II)phthalocyanine tetrasulfonate (CPTS), is described. Multilayered CPTS and polydiallyldimethylammonium chloride (PDADMAC) were alternately assembled on different planar substrates via the layer-by-layer (LbL) procedure. The growth of CPTS multilayers was monitored by UV-visible spectrometry and quartz crystal microbalance (QCM) measurements. Both the UV-visible spectra and the QCM data showed that a fixed amount of CPTS could be attached to the substrate surface for a given adsorption cycle. Cyclic voltammograms at the CPTS/PDADMAC-covered gold electrode exhibited a decrease in peak currents with the layer number, indicating that the permeability of CPTS multilayers on the electrodes had diminished. When these CPTS multilayered films were calcined at elevated temperatures, uniform thin films composed of nanoparticulate copper oxide could be produced. Ellipsometry showed that the thickness of copper oxide nanoparticulate films could be precisely tailored by varying the thickness of CPTS multilayer films. The morphology and roughness of CPTS multilayer and copper oxide thin films were characterized by atomic force microscopy. X-ray diffraction (XRD) measurements indicated that these thin films contained both CuO and Cu2O nanoparticles. The preparation of such copper oxide thin films with the use of metal complex precursors represents a new route for the synthesis of inorganic oxide films with a controlled thickness.

Adsorption↗
PubMed2004

Dispersion properties of an alumina nanopowder using molecular, polyelectrolyte, and steric stabilization.

A commercial alumina nanopowder was characterized and its dispersion was studied using electrostatic, electrosteric, and steric surfactants. Citric acid was used as the electrosteric dispersant, ammonium polymethacrylic acid (Darvan C) as the electrosteric dispersant, and Hypermer KD-1 in alpha-terpineol as a purely steric system. Phase stability in water was examined by X-ray diffraction, and the surface chemistry was characterized by zeta potential and isoelectric points. Rheology measurements were used to study the impact of each dispersant type on maximum solids loading, with the maximum loading being achieved for the polyelectrolyte dispersant. Differences in maximum solids loading are related to the excluded volume of the particle separation distance induced by each stabilizing interaction.

Aluminum Oxide↗
PubMed2006

Preparation and characterization of stimuli-resistible hydrogels nano-coated with polyelectrolyte multilayer films.

Alginate (ALG) hydrogels were nano-coated with polyelectrolyte multilayer (PEM) films composed of poly(diallyldimethyl ammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS). Non- and nano-coated ALG hydrogels were immersed into salt solutions (pH 6, ionic strength: 0.01 M), and the swelling behavior of these ALG hydrogels was observed by optical microscopy. The increases in the diameter of the 10-step coated ALG hydrogels were one fourth or less than that of the non-coated hydrogels. These results indicate that the characteristics of nano-coated ALG hydrogels remain unchanged independent of how the external environment is changed (e.g., pH, ionic strength). Consequently, tolerant ionic hydrogels may be prepared by the nano-coating of hydrogel surfaces with PEM films and may be useful for technological and biomedical applications.

Absorption↗
PubMed2006

Oxidation-reduction dynamics in layer-by-layer self-assembled redox polyelectrolyte multilayer modified electrodes.

The oxidation-reduction dynamics of layer-by-layer (LbL) self-assembled redox polyelectrolyte multilayer films on electrodes has been studied by cyclic voltammetry, chrono-amperometry, electrochemical quartz crystal microbalance (EQCM), ellipsometry, and Fourier transform reflection-absorption infrared spectroscopy (FT-IRRAS). Thin layer electrochemistry with fast electron transfer at the underlying metal-film interface and charge propagation by electron hopping between adjacent redox sites in the finite thin film has been observed. An almost ideal cyclic voltammetry for a fixed number of redox sites in the thin surface film suggests that the multilayer can be fully oxidized and reduced in the time scale of the experiment (RT/vF > or = 0.05 sec). The electron hopping diffusion coefficient 3 x 10(-10) cm2 s(-1) was obtained from the chronoamperometric current transient and the ellipsometric thickness. Both cyclic voltammetry and potential step yield a surface osmium bipyridyl redox concentration of gamma Os = 4 x 10(-10) mol x cm(-2) for (PAH-Os)5(PVS)4 film. Exchange of ions and solvent occur simultaneously to the charge injection as revealed by the EQCM mass change and the ellipsometric thickness change. From the end-to-end mass-to-charge linear relationship, the molar mass of the ionic and neutral species exchanged largely exceeds the molar mass of any ions or solvent which suggests an important flux of solvent during redox switching. An initial "break in" effect is observed for the first oxidation-reduction cycles when a newly self-assembled film equilibrates with the electrolyte as charge is injected during the electrochemical perturbation.

Electrochemistry↗
PubMedDate not supplied

Intracellular delivery of poly(ethylene glycol) conjugated antisense oligonucleotide using cationic lipids by formation of self-assembled polyelectrolyte complex micelles.

A polyelectrolyte complex (PEC) micelle-based antisense oligodeoxynucleotide (ODN) delivery system was designed to overcome intrinsic limitations of cationic lipid-mediated gene transfer. Cationic lipid (Lipofectamine, LF) and ODN conjugated poly(ethylene glycol) (PEG) were ionically complexed to form self-assembled spherical PEC micelles. They have a distinctive structural feature: a charge-neutralized core surrounded by highly flexible PEG corona. The PEC micelles could be visualized as a nano-sized sphere by atomic force microscopy (AFM). The DNA/LF PEC micelles exhibited far improved transfection efficiency compared to those of conventional lipoplex formulations (ODN/LF) in the presence of serum. They showed enhanced cellular uptake followed by rapid nuclear localization of ODN in human epithelial carcinoma (KB) cells. In addition, anti-proliferative activity of c-raf gene-directed antisense ODN was almost fully maintained in KB cells in the presence of serum.

Cations↗
PubMed2001

Interactions among proteins and hydrophobically modified polyelectrolytes.

A special class of hydrophobically modified polyelectrolytes was studied wherein poly(acrylic acid) (PAA) was conjugated with Pluronic F127 NF surfactant. The Pluronic-PAA copolymer solutions form gels at low concentrations when exposed to bodytemperature. Such gels possess enhanced retention in topical applications. Circular dichroism spectra indicate that tertiary structures of human insulin, haemoglobin, and albumin were stabilized in solutions of Pluronic-PAA. Aggregation of insulin in gelled solutions of Pluronic-PAA was impeded as demonstrated in shaking tests. The presence of Pluronic-PAA hindered the insulin degradation by alpha-chymotrypsin by at least 7-fold. Extraction of calcium ions from trypsin by Pluronic-PAA led to the dramatic changes in the tertiary structure and total loss of enzymatic activity, suggesting that Pluronic-PAA could inhibit tryptic degradation of proteins.

Acrylic Resins↗
PubMed2006

Imaging cell interactions with native and crosslinked polyelectrolyte multilayers.

The adhesion of primary chondrocytes to polyelectrolyte multilayer films, made of poly(l-lysine) (PLL) and hyaluronan (HA), was investigated for native and crosslinked films, either ending by PLL or HA. Crosslinking the film was achieved by means of a water-soluble carbodiimide in combination with N-hydroxysulfosuccinimide. The adhesion of macrophages and primary chondrocytes was investigated by microscopical techniques (optical, confocal, and atomic), providing useful information on the cell/film interface. Native films were found to be nonadhesive for the primary chondrocytes, but could be degraded by macrophages, as could be visualized by confocal laser scanning microscopy after film labeling. Confocal microscopy images show that these films can be deformed by the chondrocytes and that PLL diffuses at the chondrocyte membrane. In contrast, the cells adhered and proliferated well on the crosslinked films, which were not degraded by the macrophages. These results were confirmed by a MTT test over a 6-d period and by atomic force microscopy observations. We thus prove that chemical crosslinking can dramatically change cell adhesion properties, the cells being more stably anchored on the crosslinked films.

Animals↗
PubMed2006

Chitosan as cationic polyelectrolyte for the modification of electroosmotic flow and its utilization for the separation of inorganic anions by capillary zone electrophoresis.

Cationic polyelectrolyte of chitosan was used for the reversal of electroosmotic flow in capillary zone electrophoresis. The chitosan was dissolved in acetic acid solution, and stable electroosmotic flow was obtained at the chitosan concentrations between 50 and 300 microg/mL. Separation of inorganic anions was carried out using the dynamically coated capillary by capillary zone electrophoresis. Nine kinds of anions were separated and detected with the capillary. The electrophoretic mobility of the analyte anions decreased with increasing concentrations of chitosan in the migrating solution through ion-ion interaction, but the migration order of the analyte anions was not changed in the concentration range of the chitosan examined. The signal shape for the analyte anions was developed by using field-enhanced sample stacking with 10 mM sodium sulfate.

Journal Article↗
PubMed2003

Polyelectrolyte surface interface for single-molecule fluorescence studies of DNA polymerase.

We report the use of polyelectrolyte multilayers in a stable robust surface chemistry for specific anchoring of DNA to glass. The nonspecific binding of fluorescently tagged nucleotides is suppressed down to the single-molecule level, and DNA polymerase is active on the anchored DNA template. This surface-chemistry platform can be used for single-molecule studies of DNA and DNA polymerase and may be more broadly applicable for other situations in which it is important to have specific biomolecular surface chemistry with extremely low nonspecific binding.

Biotinylation↗
PubMedDate not supplied

p-Nitrophenetole deethylase activity of rat liver microsomes entrapped in polyelectrolyte capsules.

Liver microsomes from phenobarbital induced rats are entrapped in capsules prepared from polyelectrolytes. A comparative analysis of the deethylase activity against p-nitrophenetole by encapsulated and freely suspended microsomes is carried out. The pH optimum occurs at about 7.2 for encapsulated as well as free microsomes. The pH activity profile of encapsulated microsomes, however, is strongly flattened. The maximal velocity of entrapped microsomes is about a quarter of that of free microsomes. The Michaelis-Menten constants are virtually equal. Despite of the lowered activity of encapsulated microsomes this kind of immobilization of enzymes may be useful in biotechnology and medicine because mild immobilization conditions like room temperatures and aqueous solutions are realized.

Animals↗
PubMed1998

STM studies of LB films of amphiphilic polyelectrolytes with antibodies and enzymes.

The structure of LB films of protein-polyelectrolyte complexes transferred onto the pyrographite surface was studied by STM. The images of the films obtained at various protein concentrations in the water subphase and different values of surface pressure were captured. The topology of the surface covered by one or three layers of the films studied was investigated. It is shown that at a protein concentration of 1 mg/ml in the water subphase, the films are composed of aggregated protein molecules, and their structure has an insular character. An increase in the number of transferred layers up to three results in a virtually complete covering of the surface. A decrease in the protein concentration in the water subphase to 1 microgram/ml enabled us to prepare films consisting of individual non-aggregated protein molecules.

Antibodies↗
PubMedDate not supplied

[Conformation and molecular and ionic transformations of polycytidylic acid immobilized in multilayer Langmuir and polyelectrolyte films].

Multilayer films of complexes of polycytidylic acid with dioctadecyldimetylammonium were obtained by the Langmuir-Blodgett method (LB films), and complexes of poly(C) with polycations (poly-L-lysisne, polyethyleneimine, polyallylamine) were obtained by the method of alternate adsorption (polyionic assembly) from solutions of oppositely charged polyelectrolytes on the solid carrier (SA films). It was shown that poly(C) exists in SA films in a single-stranded state irrespective of whether in the starting solution it occurred in the single-stranded nonprotonated or double-stranded protonated conformation. Conversely, in the LB film poly(C) preferred to be in a double protonated conformation. UV-spectra of water-insoluble LB and SA films at different pH values of surrounding water medium were investigated. Proton titration curves of poly(C) immobilized in LB films were obtained. The analysis of the shape of titration curves showed that the molecular-ionic transformation of poly(C) in LB films is accompanied by both the conformational transition of the polynucleotide and the molecular rearrangement in the whole film. Poly(C) was found to transform from the double- to single-stranded state and vice versa in the "deprotonation-protonation" cycle of LB film due to cooperative release/binding of hydrogen ions by cytosine bases. In contrast, poly(C) "protonation-deprotonation" in SA films occurred without conformational transitions of the polynucleotide. As opposed to poly(C) in solution a rather big hysteresis of forward and back titration curves was found for both types of multilayer films, indicating molecular rearrangements in films. The reason for the structural transformations of poly(C) upon fabrication of LB or SA films and the mechanism of molecular ionic transformations of poly(C) in films are discussed in terms of a simple model of ion exchange. An assumption about the nature of structural transformations of LB and SA films during their protonation-deprotonation is put forward.

Electrolytes↗
PubMed1999

Cultivation of encapsulated yeast cells in NaCS-PDMDAAC polyelectrolyte complexes.

The cultivation of encapsulated S. cerevisiate and C. utilis in NaCS-PDMDAAC Polyelectrolyte Complexes was studied. The results showed that these two kinds of encapsulated microorganisms showed the same growing properties as in their free cell cultures, and thus NaCS-PDMDAAC microcapsules were suitable for the encapsulation of biological substances. The encapsulated S. cerevisiate cells were fermented sequentially for 16 batches. The highest cell density in the capsules reached 2.64 x 10(10) cells/mL and ethanol concentration reached 47.0 g/L. The encapsulated C. utilis produced the same amount of GSH as the free cell culture.

Ammonium Chloride↗
PubMed2000

Lipid-DNA and lipid-polyelectrolyte mesophases: structure and exchange kinetics.

Cationic lipid-DNA complexes are used as gene transfer vehicles in molecular biology and potentially in human gene therapy. In recent synchrotron X-ray scattering studies the molecular structure of such self-assembling aggregates was elucidated. A rich polymorphism of lamellar, hexagonal, lamellar-columnar and micellar mesophases was found. In this article we describe composite phases of cationic lipid mixed with hyaluronic acid and dextran sulfate which likewise form intercalated lamellar complexes. Heterogeneous phases of lipid/dextran sulfate mixed with lipid/DNA exhibit macroscopic phase separation. When dextran sulfate is added to preformed cationic lipid DNA complexes the latter are dissolved in favor of the lipid-polyelectrolyte phases. We investigated the kinetics of the DNA replacement by dextran sulfate. The experiments are intended to mimic the interaction of cationic lipid gene delivery complexes with highly charged extracellular matrix components.

Animals↗