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PubMed2005

Electric birefringence study of an amyloid fibril system: the short end of the length distribution.

In this article, a system of amyloid fibrils, based on the protein beta-lactoglobulin, is studied by transient electric birefringence. Single pulses of an electric field were applied to the solution, and the initial rise and subsequent decay of birefringence analysed. The decay takes place on a range of relaxation times, and therefore contains information about the length distribution of fibrils in the system. The information can be extracted using theories of the electric polarisability of polyelectrolyte rods, since the fibrils are an example of these. Despite the long-standing complications of such theories, useful quantitative information about the system can still be obtained. Using the Fixman model of polyelectrolyte polarisability, we obtain a measurement of the short end of the length distribution which shows the fibril concentration as a function of length rising linearly from 0.02-2 microm. The short end of the length distribution was unobtainable in our previous study using rheo-optics (S.S. Rogers et al., Macromolecules 38, 2948 (2005)), but reasonable agreement between the two techniques shows they are complementary.

Amyloid↗
PubMed2004

In vitro mineralization of gelatin-polyacrylic acid complex matrices.

Gelatin-polyacrylic acid (gel-PAA) matrices were obtained by slow diffusion of polyacrylic acid into gelatin gels. The matrices were submitted to uniaxial stretching, which induces a preferential orientation of the collagen molecules, and used as biomimetic substrates for the nucleation of hydroxyapatite from simulated body fluid (SBF). The relative amount of hydroxyapatite deposited from 1.5SBF increases as a function of polyelectrolyte content in the matrices, up to about 30 wt%. In the absence of PAA, the inorganic phase is laid down on the surface of the gelatin matrices as hemispherical aggregates. At variance, hydroxyapatite deposition in the gel-PAA composite matrices at relatively low PAA content occurs preferentially in the spaces between the layers on the surface of the matrices and displays a tablet-like morphology. At high polyelectrolyte concentration, an almost uniform layer of hydroxyapatite covers the whole surface of the matrices. The preferential orientation of the (002) hydroxyapatite reflection indicates a close relationship between the inorganic crystals and the collagen molecules.

Acrylic Resins↗
PubMed2005

Osteoblast growth promotion by protein electrostatic self-assembly on biodegradable poly(lactide).

Extracellular matrix (ECM)-like coating was developed on biodegradable biomaterials based on the electrostatic self-assembly (ESA) technique to promote osteoblast growth. Poly(ethylenimine) (PEI) was first employed to obtain a stable positively charged surface on poly (DL-lactide) (PDL-LA) substrate. Gelatin was selected as ECM-like biomacromolecule to deposit on the activated PDL-LA substrate using the ESA technique. zeta-Potential results showed alternating charge of polyelectrolytes (PEI/gelatin) layering on PDL-LA microspheres. Quartz crystal microbalance (QCM) measurement further verified the gradual deposition of PEI/gelatin on PDL-LA thin film. Osteoblast cells (MC3T3) were chosen to test the cell behavior on modified PDL-LA substrates. The osteoblast test about cell activity, intracellular total DNA content, total protein content and cell morphology by SEM investigation on ECM-like multilayer-modified PDL-LA substrate showed to promote osteoblast growth. Comparing conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. It may be a good choice for the surface modification of complex biomedical devices. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.

3T3 Cells↗
PubMedDate not supplied

Optical visualization of polymer-polymer interactions.

Surface-enhanced absorption (SEA) has been used to monitor interactions of biomolecules and to observe structural changes of polymers. Such interactions of biomolecules are of interest in high-throughput screening and diagnostics. The structural changes of synthetic polymers can be exploited in optical sensorics. Based on SEA we have developed a technique that enables us to transfer the interaction of polyelectrolytes between two flat, solid surfaces into a visible color change, exploiting nanoscopic metal clusters. The polyelectrolytes are coated onto electrochemically oxidized aluminum, glass, and polycarbonate substrates. The change of surface color is monitored with a flat-bed scanner, and the interactions are analyzed kinetically. The results are interpreted with regard to adhesion, surface tension, electrostatic interactions, and miscibility.

Colorimetry↗
PubMed2003

Examination of murine tear film.

PURPOSE: To define spatially any free aqueous layer in murine tear film. METHOD: A pre-zeroed microelectrode was touched to the superficial corneal epithelium and then raised in steps of 1 micro m through the murine tear film into the air and then retraced along the same path. Other murine tear films were partially probed with a spatial resolution of 0.1 micro m. The reference microelectrode was placed in a fragment of 3% polyacrylamide gel equilibrated against 154 mM NaCl and located on the nasal quadrant of the scleral conjunctiva. Other murine corneas were quick frozen in melting isopentane and freeze substituted or pretreated with cetylpyridinium chloride and then examined by transmission electron microscopy. RESULTS: The recorded electrical profiles of the tear film were reproducible in each preparation and showed a relatively uniform positive electrical potential throughout their whole thickness, except within 0.5 micro m of the epithelial surface when the potential reversed to negative values. The thickness of mouse tear film averaged 7.4 +/- 0.8 micro m (mean +/- SD, n = 40). The electron microscope images showed the murine tear film to have a relatively uniform positive electron density throughout the thickness. CONCLUSIONS: Electrical profiles of the murine tear film presented no evidence of a separate free aqueous phase. The tear film is observed as an aqueous gel that includes anion-exchanging polyelectrolytes throughout most of its thickness, but within 0.5 micro m of the epithelial surface, it changes to cation-exchanging polyelectrolytes. Electron microscope images provide some supporting evidence.

Animals↗
PubMed2006

Influence of anaerobic digestion on particle surface charge and optimal polymer dosage.

Anaerobic digestion leads to significant changes of the sludge structural matrix, affecting particle size distribution and dewaterability. The surface charge, determined by means of streaming current, can be effectively used to monitor the complex phenomena of floc disruption, colloid formation and chemical conditioning. To study the relation between surface charge and optimal dosage, two different cationic polyelectrolytes were used: Praestol 644, polymer with high molecular weight and low charge density, and Poly Dadmac, with relatively low molecular weight but high charge density. The optimal Poly Dadmac dosage strictly met the value required to neutralise particle charge whereas the optimal dosage of Praestol 644 indicated that the relevant charge was considerably lower than the one required for charge neutralisation. Mechanisms of action are therefore clearly different. Another objective was to investigate the changes of dewatering characteristics of secondary sludge during anaerobic digestion tests at different inoculum content by determining charge density, and optimal polymer dosage. The optimal polyelectrolyte dosage remains almost constant during digestion at high inoculum, but a significant increase in the first period is observed at low inoculum, thus suggesting that the release of colloidal and supracolloidal material from sludge affects dewaterability, especially in the first days of digestion.

Anaerobiosis↗
PubMed1989

Formation of hydroxyapatite in hydrogels from tetracalcium phosphate/dicalcium phosphate mixtures.

Apatitic calcium phosphate cements, formed by the ambient reaction of tetracalcium phosphate (TTCP) with dicalcium phosphates (DCP), have been recently reported. H2O or dilute aq. H3PO4 (0.2%) is used as the liquid vehicle for this reaction. The aim of this study was to ascertain if hydroxyapatite (HAp) can form in self-cured hydrogel composites containing TTCP/DCP mixes. The setting times (ST) and diametral tensile strengths (DTS) of these hydrogel composites were also determined. The hydrogels were of two types: (1) vinyl thermosets derived from the copolymerization of HEMA (2-hydroxyethyl methacrylate) and cross-linking monomers, and (2) polyelectrolyte-based hydrogels formed from aq. poly(alkenoic acids), e.g., poly(acrylic acid). Cylindrical specimens 6 mm D x 3 mm H were prepared and stored in H2O for up to 30 days. The HEMA composites were hardened in 7-15 min by free radical initiation (benzoyl peroxide/tertiary aromatic amine). The polyelectrolyte cements were hardened in 6-8 min. After various periods of storage in H2O at 37 degrees C, some of the specimens were examined by X-ray spectroscopy for HAp. HAp formation was not observed in the HEMA composites even after 30 days of H2O storage but was detected in the polyacid cements. The 24-h DTS values of the HEMA composites (14-26 MPa) were higher than those of the polyacid cements (7-12 MPa). Both the H2O content and pH may thus be factors controlling the rate and extent of HAp formation in hydrogel composites containing TTCP/DCP mixtures.

Calcium Phosphates↗
PubMedDate not supplied

Release behaviour of 5-fluorouracil from chitosan-gel microspheres immobilizing 5-fluorouracil derivative coated with polysaccharides and their cell specific recognition.

In order to provide a device releasing drugs in a controlled manner and having targetability to specific organs or cells, chitosan-gel microspheres, CMS, crosslinked with glutaraldehyde, immobilizing 1-[N-(5-aminopentyl) carbamoyl]-5-fluorouracil, 1, coated with anionic polysaccharides, such as 6-O-carboxymethyl-N-acetyl-alpha-1,4-polygalactosamine (CM-NAPGA), 6-O-carboxymethyl-chitin, alginic acid and heparin, by polyelectrolyte complex membrane formation were prepared. When chitosan was crosslinked with glutaraldehyde, 1 was simultaneously immobilized into CMS by Schiff's base formation. Average diameter of CMS obtained was estimated to be about 0.5-1.0 micron by SEM observation. In physiological saline media, only free 5-FU was released from the CMS but 1 and any 5-FU derivative was not. Release rate of 5-FU from the CMS was reduced by coating with polyelectrolyte complex membrane of cationic chitosan and anionic polysaccharides. CMS coated with CM-NAPGA showed a lectin-mediated specific aggregation phenomenon by addition of Abrus precatorius agglutinin. Moreover, the CMS immobilizing 1 coated with CM-NAPGA showed higher growth-inhibitory effect against SK-Hep-1 (human hepatoma) cells in vitro than the CMS coated with other polysaccharides.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Modelling of gas transport function of erythrocytes in haemoglobin sorption immobilization.

Colloid-disperse systems based on haemoglobin sorption immobilization in reticular polyelectrolytes are proposed and investigated. The efficiency of oxygen transport of these systems is much higher than that of native haemoglobin and is comparable with the efficacy of gas transport of erythrocytes. This is believed to be due to highly selective sorption immobilization of haemoglobin in microdisperse forms of permeable carboxylic reticular polyelectrolytes. Microparticles exhibit high local concentration of haemoglobin, the protein mass being by one order of magnitude higher than that of the polymer carrier.

Biological Transport, Active↗
PubMed1993

Prolonged biochemical and morphological stability of encapsulated liver cells--a new method.

In this work a new type of polyelectrolyte complex capsules is introduced as an artificial housing for liver cells. Male Wistar rat hepatocytes were encapsulated using cellulose sulphate and polydimethyldialyllammonium chloride as polyelectrolytes. Amino acid metabolism rate and urea synthesis of the cells increased over the investigation period in contrast to the decrease observed in control monolayer cultures. The encapsulated cells were morphologically characterized. The described procedure represents a sufficient method for the cultivation of living cells in mechanically stable semipermeable microcapsules.

Amino Acids↗
PubMedDate not supplied

[Induction of posterior detachment of the vitreous body by intraoperative vitreo-syneresis with injection of water-soluble polymers (an experimental-morphological study)].

The capacity of water-soluble polymers (polyethylenimine, polyvinylpyrrolidone with copolymers) to induce posterior detachment of the vitreous by its rapid condensation (vitreosynerysis) was studied in experiments on 14 rabbits. Histological studies showed that water-soluble polymers specifically react forming complexes with components of the vitreous. The vitreous shrinks under the effect of polyelectrolytes (vitreosynerysis), which leads to its posterior detachment 1.5 h after injection of the polymer into the vitreous cavity: complete detachment was attained in 2 animals and partial in 8. The degree of vitreosynerysis depends on the complex-forming activity of polyelectrolytes towards the vitreous components. Polymers used in our study exerted no toxic or traction effects on the adjacent structures of the eye.

Animals↗
PubMed2001

Water and the cytoskeleton.

The diffusion of intracellular fluid and solutes is mainly limited by the density and the geometry of crossbridges between cytoskeletal polymers mediating the formation of an integrated cytoplasmic scaffold. Evidence for specific relationships between water and cytoskeletal polymers arises from the effect of heavy water on their polymerization process in vitro and on the cytoskeleton of living cells. The hydration of cytoskeletal subunits is modified through polymerization, a mechanism which may be involved in the direct contribution of the cytoskeleton to the osmotic properties of cells together with changes of hydration of polymers within networks. The dynamic properties of the hydration layer of cytoskeletal polymers may reflect the repetitive distribution of the surface charges of subunits within the polymer lattice, thus inducing a local and long range ordering of the diffusion flows of water and solutes inside polymer networks. The interactions between subunits in protofilaments and between protofilaments determine the specific viscoelastic properties of each type of polymer, regulated by associated proteins, and the mechanical properties of the cell through the formation of bundles and gels. Individual polymers are interconnected into dynamic networks through crossbridging by structural associated proteins and molecular motors, the activity of which involves cooperative interactions with the polymer lattice and likely the occurence of coordinated modifications of the hydration layer of the polymer surface. The cytoskeletal polymers are polyelectrolytes which constitute a large intracellular surface of condensed anionic charges and form a buffering structure for the sequestration of cations involved in the regulation of intracellular events. This property allows also the association of cytoplasmic enzymes and multimolecular complexes with the cytoskeleton, facilitating metabolic channelling and the localization of these complexes in specific subdomains of the cytoplasm. The consequences of interactions between membranes and the cytoskeleton in all cellular compartments range from the local immobilization and clustering of lipids and membrane proteins to the regulation of water and ion flows by the association of cytoskeletal subunits or polymers with transmembrane channels. The possibility that the polyelectrolyte properties of the cytoskeletal polymers contribute to the modulation of membrane potentials supports the hypothesis of a direct involvement of the cytoskeleton in intercellular communications.

Actins↗
PubMedDate not supplied

Immobilization of biocomponents for immune optical sensors.

Immobilisation of both human immunoglobulin(IgG) and antiimmunoglobulin (anti-IgG) was performed by means of polyelectrolyte self-assembly. This technique was compared with direct immobilisation of the immune components on bare gold and their covalent binding via glutaraldehyde as a bifunctional reagent. Additionally, the immune components were properly oriented during their immobilisation by using a predeposited layer of the protein A. Methods of the surface plasmon resonance (SPR) and planar interferometry were employed for monitoring the immobilisation as well as specific immune reaction. It was shown that in case of the use of polyelectrolyte self-assembly it is possible to achieve the sensitivity of the analysis up to 30 ng/ml for SPR and up to 1 ng/ml for planar interferometer based immune sensors.

Autoantibodies↗
PubMed2002

Novel polypeptide-comprising biopolymer systems.

Covalent bioconjugation between anionic polyelecrolytes and polypeptide antigens chemically synthesized by solid-phase chemistry, were studied in hydrated reversed micelle systems. The epitops of Foot-and-Mouse disease virus VP1 protein (40--60 and 135--160 residues) were used as polypeptide antigens. The polypeptide-comprising Biopolymer Systems were obtained by two methods: 1) Inclusion of peptides into electrostatic polyelectrolyte complexes of polycations with proteins, 2) Inclusion of peptides into Cu(+2)-induced polyelectrolyte complexes of polyanions with similarly (anionic) charged proteins. The immunogenetic properties of polymer-peptide conjugates and peptide-comprising Biopolymer Systems were investigated and the specificity of antibodies produced was analyzed. Polymer-Peptide conjugates, as well as peptide-comprising Biopolymer Systems appeared to possess a high peptide specific immunogenecity even without the addition of traditional adjuvants. It was found that PE-BSA.FMD.Ag conjugates conferred effective immunoprotection against Foot-and-Mouth disease virus.

Animals↗
PubMed2003

[Conjugated polymer-subunit immunogens and vaccines].

A study of fundamental mechanisms regulating the immune response resulted in producing a theory explaining the mechanism of immunostimulating properties of polyelectrolytes, as well as in working out the principles for creating the synthetic immunomodulators and, on the basis of them, polymer-subunit immunogens and vaccines. The above theory produced a basis for creating polyoxidonium, a new polymer polyelectrolyte, which was used to synthesize the conjugated polymer-subunit "Grippol" vaccine that, after its commissioning into production, has been widely used.

Adjuvants, Immunologic↗
PubMed2004

Monitoring floc formation and breakage.

Monitoring of flocculation processes is of great practical importance and can give very useful information on the action of different coagulants under various conditions. It is shown that a continuous optical monitoring technique provides a convenient means of following the formation, break-up and regrowth of flocs under standard mixing and stirring conditions. Examples of results using this approach are given, with alum and PACl coagulants as well as a cationic polyelectrolyte. PACl products give larger flocs than with alum, but they show about the same relative degree of breakage when the shear rate is increased. With all of these coagulants, floc breakage is not fully reversible; i.e. flocs only re-grow to a limited extent when the shear rate is reduced. This is in marked contrast to the action of a cationic polyelectrolyte, where floc breakage is almost completely reversible. Some possible reasons for these observations are discussed, but, so far, there is no adequate model available.

Alum Compounds↗
PubMed2004

The effects of polymer characteristics on nano particle separation in humic substances removal by cationic polymer coagulation.

Removal of humic substances by coagulation involves nano- and microparticle transport processes. The objective of this paper has been to describe the effects of polymer characteristics on the initial coagulation of nano-sized humic substances and on the aggregates' ability to form larger flocs. The study offers a direct comparison of four different low molecular weight polycations, with charge densities ranging from 4.0 to 7.0 meq/g, as well as of a low and medium molecular weight cationic polyacrylamide with practically equal charge densities. The extent of coagulation of humic substances, determined as the percentage removal of humic substances after filtration through 0.1 microm, could, regardless of the polymer type, be explained by the amount of cationic charge equivalents added per mg TOC of humic substances. The optimal polymer dosage with respect to the extent of flocculation, determined as the percentage removal after filtration through 11 microm could not be explained by this, but the maximum extent of flocculation obtained with each polymer type increased with increasing polyelectrolyte charge density. However, the weak polycation chitosan showed a significantly higher maximum extent of flocculation than would be predicted from its charge density. Polyelectrolyte molecular weight did not show any significant effect on the coagulation of humic substances, nor did it increase the extent of floc separability at 11 microm.

Cations↗
PubMed1987

The charge effects of the self-diffusion constant of bovine mercaptalbumin.

The charge effect on the translational self-diffusion constant, D, of polyelectrolytes has been quantitatively analyzed based on dynamic light scattering experiments. Perfectly monodisperse bovine mercaptalbumin has been used at low pH as a positively charged polyelectrolyte sample. Completely linear plots of log{g2(t)-1} vs. time t have been obtained for uncharged states of the protein, for the cor relation function of the scattered light intensity, g2(t). The plots deviate from linearity as polyions bear the charges. The D values for various ionic states, obtained from the initial slopes of the plots, have been analyzed using the simple theory of Imai and Mandel (N. Imai and M. Mandel, Macromolecules 15 (1982) 1562) derived based on the Onsager-Navier-Stokes equation for solvent flow with counterion distribution around a polyion. It has turned out that the experimental D values coincide well with the theory and that the characteristic nature of D can be elucidated principally from the charge effect.

Journal Article↗