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PubMed2006

Surface plasmon resonance spectroscopy study of electrostatically adsorbed layers.

The use of 4-(dimethylamino)pyridine to form an adhesion layer for the adsorption of anionic polyelectrolytes on gold surfaces is investigated. In situ surface plasmon resonance spectroscopy is used to monitor the changes in thickness of the adsorbed layers as a function of pH changes. Weak (poly(acrylate)) and strong (poly(styrenesulfonate)) polyelectrolytes have been studied. Although 4-(dimethylamino)pyridine is weakly bound to gold, it is not displaced by these polyelectrolytes and acts as an adhesion layer. The relationship of the interaction of anionic polyelectrolytes with 4-(dimethylamino)pyridine-modified planar gold and gold nanoparticles is discussed.

4-Aminopyridine↗
PubMed2006

Layer-by-layer-assembled microfiltration membranes for biomolecule immobilization and enzymatic catalysis.

Multilayer assemblies of polyelectrolytes, for protein immobilization, have been created within the membrane pore domain. This approach was taken for two reasons: (1) the high internal membrane area can potentially increase the amount of immobilized protein, and (2) the use of convective flow allows uniform assembly of layers and eliminates diffusional limitations after immobilization. To build a stable assembly, the first polyelectrolyte layer was covalently attached to the membrane surface and inside the pore walls. Either poly(L-glutamic acid) (PLGA) or poly(L-lysine) (PLL) was used in this step. Subsequent deposition occurs by multiple electrostatic interactions between the adsorbing polyelectrolyte [poly(allylamine) hydrochloride (PAH) or poly(styrenesulfonate) (PSS)] and the oppositely charged layer. Three-layer membranes were created: PLL-PSS-PAH or PLGA-PAH-PSS, for an overall positive or negative charge, respectively. The overall charge on both the protein and membrane plays a substantial role in immobilization. When the protein and the membrane are oppositely charged, the amount immobilized and the stability within the polyelectrolyte assembly are significantly higher than for the case when both have similar charges. After protein incorporation in the multilayer assembly, the active site accessibility was comparable to that obtained in the homogeneous phase. This was tested by affinity interaction (avidin-biotin) and by carrying out two reactions (catalyzed by glucose oxidase and alkaline phosphatase). Besides simplicity and versatility, the ease of enzyme regeneration constitutes an additional benefit of this approach.

Adsorption↗
PubMed2005

The microrheology of polystyrene sulfonate combs in aqueous solution.

Video particle tracking (VPT) and diffusing wave spectroscopy were used to characterize the microrheology of polystyrene sulfonate combs in aqueous solutions. At low frequencies VPT demonstrated predominantly viscous behavior. The manner in which the viscosity scaled as a function of monomer concentration was a sensitive function of the comb architecture. Densely branched combs or combs with long side chains demonstrated entangled polyelectrolyte scaling above the overlap concentration, whereas sparsely branched combs had unentangled polyelectrolyte scaling. A dynamic scaling model was developed for the viscosity of unentangled semidilute solutions of comb polyelectrolytes. Diffusing wave spectroscopy demonstrated Rouse modes (G' approximately G" approximately omega12) for the high-frequency dynamics of the semidilute comb solutions. The form of the high-frequency viscoelasticity was independent of the chain architecture and the modulus scaled as expected for linear flexible polyelectrolytes.

Journal Article↗
PubMed2005

Conventional approach for abattoir wastewater treatment.

Detailed physico-chemical studies on abattoir effluent using lime, alum, ferrous sulphate and an anionic polyelectrolyte were tried individually and in combination. Among the coagulants tried, lime resulted in good settling of the sludge. At 400 mg l(-1) of lime dose, the Suspended Solids (SS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) removals were found to be 41.9%, 38.9% and 36.1%, respectively. Best results were obtained with lime and ferrous sulphate in a combination ratio of 400:100 mg l(-1), and the COD reduction of 36.1% at 400 mg l(-1) of lime, further improved to 56.8%. Lime and alum dose of 400:50 mg l(-1) resulted in an increased COD reduction of 42.6% compared to 36.1% at lime dose of 400 mg l(-1). However, the same lime dose with ferrous sulphate addition of 100 mg l(-1) resulted in an increased COD reduction of 56.8% compared to 36.1%. This is a more efficient option for abattoir wastewater treatment and also cost effective. Ferrous sulphate with anionic polyelectrolyte resulted in good removals. Though it is a costly chemical, the dose needed is just half that of lime and just 0.1 mg l(-1) of anionic polyelectrolyte resulted in good reductions in SS, BOD and COD of 54.2%, 49.6% and 43.8% respectively. Studies indicated that the lime and ferrous sulphate in the combination of 400:100 mg l(-1), and ferrous sulphate and polyelectrolyte in the combination of 100:0.1 mg l(-1) are the two feasible options. Lime in combination with alum can also be applied but resultant sludge volume would be more.

Abattoirs↗
PubMed2005

Comparison of selective attachment and growth of smooth muscle cells on gelatin- and fibronectin-coated micropatterns.

Tissue engineering research has been on going for many years, people are making all the effort to explore the cell functions in cellular level and even in molecular level. Making the cells functional in an in vitro environment is a preliminary goal for the implantation and repair of complicated tissues/organs. Fabricating artificial ECM to mimic the in vivo environment is an essential approach in tissue engineering. The work in this paper is to study how rat aorta smooth muscle cells (RASMCs) behave in two engineered cell culture scaffolds: gelatin- and fibronectin (FN)-coated micropatterns. The investigation on the initial attachment and further growth of SMCs cultured on gelatin- and FN-coated micropatterns was addressed. This study focused on both the characterization of gelatin and fibronectin assembly properties and cell responses to these two protein-coated micropatterns. Thin film patterns with gelatin and fibronectin coatings were fabricated on microscope glass slides using photolithography, electrostatic layer-by-layer self-assembly and lift-off (LbL-LO) technologies. In this work, the scaffolds were built up by commonly used polyelectrolyte materials and proteins through LbL process, containing cationic poly(diallyldimethylammonium chloride) (PDDA), poly(allylamine hydrochloride) (PAH), anionic poly(sodium 4-styrenesulfonate) (PSS), gelatin and fibronectin. The resulting polyelectrolyte thin films were characterized by contact angle (CA), quartz crystal microbalance (QCM), atomic force microscopy (AFM), and fluorescence microscopy. CA measurement shows the consistent hydrophylicity of gelatin surfaces in different number of layers with LbL deposition method. Different from our previous QCM measurement of gelatin, fibronectin does not show high electrostatic attraction to either positively or negatively charged polyelectrolytes, although it can be weakly assembled to both polyelectrolyte surfaces. AFM images show Gelatin- and FN-coated micropatterns are around 50-60 nm thick. RASMCs were cultured on these gelatin- and FN-coated micropatterns. It was observed that, for the cells cultured on gelatin-coated micropatterns, they initially landed on the gelatin-coated surface, not on the PDDA-coated surface in between. But further growth of the cells was affected by the shape of the patterns: strip pattern limited cell growth beyond the patterns, but square patterns could not. While, it was found interestingly, for the cells cultured on FN-coated micropatterns, SMCs initially landed on PDDA-coated surface, and then migrated to FN-coated both square and strip patterns. These findings indicate that both gelatin and fibronectin are adhesive proteins, but they have different effects on the initial attachment and later growth for SMCs.

Animals↗
PubMed2006

Sequestration of biogenic amines by alginic and fulvic acids.

The interaction of natural (alginic and fulvic acids) and synthetic (polyacrylic acid 2.0 kDa) polyelectrolytes with some protonated polyamines [diamines: ethylendiamine, 1,4-diaminobutane (or putrescine), 1,5-diaminopentane (or cadaverine); triamines: N-(3-aminopropyl)-1,4-diaminobutane (or spermidine), diethylenetriamine; tetramine: N,N'-bis(3-aminopropyl)-1,4-diaminobutane (or spermine); pentamine: tetraethylene-pentamine; hexamine: pentaethylenehexamine] was studied at T=25 degrees C by potentiometry and calorimetry. Measurements were performed without supporting electrolyte, in order to avoid interference, and results were reported at I=0 mol L(-)(1). For all the systems, the formation of (am)L(2)H(i) species was found (am=amine; L=polyelectrolyte; i=1...4, depending on the amine considered). The stability of polyanion-polyammonium cation complexes is always significant, and for high-charged polycations, we observe a stability comparable to that of strong metal complexes. For example, by considering the formation reaction (am)H(i)+2L=(am)L(2)H(i) we found log K(i)=6.0, 6.5 and 10.8 for i=1, 2 and 3, respectively, in the system alginate-spermidine. Low and positive formation DeltaH(degrees) values indicate that the main contribution to the stability is entropic in nature. The sequestering ability of polyelectrolytes toward amines was modelled by a sigmoid Boltzman type equation. Some empirical relationships between stability, charges and DeltaG(degrees) and TDeltaS(degrees) are reported. Mean values per salt bridge of formation thermodynamic parameters (DeltaX(degrees) (n)) are DeltaG(degrees) (n)=-5.8+/-0.4, DeltaH degrees (n)=0.7+/-0.5 and TDeltaS(degrees) (n)=6.5+/-0.5 kJmol(-)(1) for all the systems studied in this work.

Alginates↗
PubMed2005

Heavy metal precipitation by polycation-polyanion complex of PEI and its phosphonomethylated derivative.

The removal of various heavy metal ions such as Cu2+, Co2+, Zn2+, Ni2+ and Pb2+ from aqueous solutions by precipitation with polyelectrolyte complex of PPEI and PEI was conducted. Heavy metal binding with PPEI was initially allowed to occur and then upon equilibration, PEI was added to initiate precipitation of the polyelectrolyte complex together with the heavy metal ion. The PPEI-PEI system was found effective for heavy metal scavenging purposes even in the presence of high concentrations of non-transition metal ions like Na+. Heavy metal concentration may be reduced beyond emission standards for industrial wastewaters. The PPEI-PEI polyelectrolyte complex was found to be more effective than traditional precipitation methods for the treatment of a representative electroless Ni plating waste solution.

Chemical Precipitation↗
PubMed2006

Improvement of dewatering capacity of a petrochemical sludge.

Oily sludge produced from a petrochemical industry was used to investigate the improvement of its dewatering properties. The oil content (OC) and the dry solid content (DS) of the raw sludge were respectively, 15% and 3.6% by weight. The capillary suction time (CST) and the specific resistance to filtration (SRF) of the raw petrochemical industrial sludge were found to be 2000s and approximately 5.5x10(16)m/kg, respectively. Conventional chemical conditioners such as alum, lime, and polyelectrolyte, and less conventional ones like fly ash, gypsum, and bentonite were used in the sludge conditioning studies. Conventional chemical conditioners gave better results for the enhancement of the dewatering capacity of the sludge. The best result was obtained by using 0.9% cationic polyelectrolyte by weight, and a decrease of 99%-95% were achieved for CST and SRF, respectively, when this dosage of cationic polyelectrolyte was used.

Alum Compounds↗
PubMedDate not supplied

Morphology of actin assemblies in response to polycation and salts.

F-actins are semi-flexible polyelectrolytes and can be assembled into a large polymer-actin complex with polymorphism through electrostatic interaction with polycations. This study investigates the structural phase behavior and the growth of polymer-actin complexes in terms of its longitudinal and lateral sizes in various polycation and KCl concentrations for a constant actin concentration. Our results show that the longitudinal growth and lateral growth of polymer-actin complexes, initiated by a common nucleation process, are dominated by different factors in subsequent growth process. This induces the structural polymorphism of polymer-actin complexes. Major factors to influence the polymorphism of polymer-actin complexes in polyelectrolyte systems have been discussed. Our results indicate that the semiflexible polyelectrolyte nature of F-actins is important for controlling the morphology and growth of actin architectures in cells.

Actin Cytoskeleton↗
PubMed2004

Clearance of minute virus of mice by flocculation and microfiltration.

Clearance of minute virus of mice (MVM) from CHO cell suspensions by flocculation and microfiltration has been investigated. MVM is a parvovirus that is recommended by the U.S. Food and Drug Administration for validating clearance of parvoviruses. The feed streams were flocculated using a cationic polyelectrolyte. Virus clearance in excess of 10,000-fold was obtained in the bulk permeate for flocculated feeds streams. However, the level of clearance was only about 10- to 100-fold for unflocculated feed streams. The results suggest that virus clearance involves interactions between the MVM particles, the cationic polyelectrolyte, and the CHO cells present. Validating virus clearance is a major concern in the biotechnology industry. New unit operations are frequently added to the purification train simply to validate virus clearance. However, many of these unit operations are less effective at validating clearance of nonenveloped viruses. Validating clearance of parvoviruses is often particularly problematic as they are nonenveloped and the virus particles are small (18 to 24 nm), making physical removal difficult. The results obtained herein indicate that addition of the cationic polyelectrolyte not only results in significant clearance of MVM but also leads to an increase in permeate flux.

Animals↗
PubMed2006

Electrophoresis of soft particles: analytic approximations.

An approximate analytic expression is derived for the electrophoretic mobility of a weakly charged spherical soft particle (i.e., a hard particle covered with a weakly charged polyelectrolyte layer) on the basis of the general mobility expression for soft particles (Ohshima, H., J. Colloid Interface Sci. 2000, 228, 190-193). The obtained mobility expression, which reproduces various approximate results so far derived and gives some new mobility formulas, covers all types of weakly charged soft particles with arbitrary values of the thickness of polymer layer, the radius of the particle core, the electrophoretic softness, and the Debye length, including spherical polyelectrolytes with no particle core as well as spherical hard particles with no polyelectrolyte layer.

Electrophoresis↗
PubMed2004

Protein electrostatic self-assembly on poly(DL-lactide) scaffold to promote osteoblast growth.

The development of protein coating on 3D biodegradable scaffold based on electrostatic self-assembly (ESA) to promote osteoblast growth is reported. Poly (ethylenimine) (PEI) was employed to obtain a stable positively charged surface on poly(DL-lactide) (PDL-LA) substrate. An extracellular-matrix (ECM)-like biomacromolecule, gelatin, was chosen as the polyelectrolyte to deposit on the activated PDL-LA substrate via ESA technique. Osteoblast (MC3T3) was then cultured on unmodified and gelatin-modified PDL-LA scaffolds. Osteoblast testing regarding total intracellular protein content, total DNA content, cell activity, and cell morphology on the ECM-like multilayer-modified PDL-LA scaffold showed that osteoblast growth was promoted. It will be easy to replace the gelatin with osteoinductive proteins or other polyelectrolytes to promote specific osteoblast functions. In comparison with conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. They may be a good choice for the surface modification of complex biomedical devices, especially for the 3D tissue-engineering scaffold. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.

3T3 Cells↗
PubMed2000

The effect of monovalent ions on polyphosphate binding to Escherichia coli exopolyphosphatase.

The thermodynamic driving force for the interaction of Escherichia coli exopolyphosphatase (PPX) with polyphosphate was investigated by varying salt choice and concentration. This interaction was found to be cation concentration independent but weakly dependent on the concentration of certain anions. Both of these traits are very uncommon for nonspecific protein-polyelectrolyte interactions. Interpretation of these results based on theory indicated that binding was not entropy driven due to release of polyelectrolyte-condensed counterions, as is the case for nearly all protein-polyelectrolyte interactions. The thermodynamics of the PPX-polyphosphate interaction showed similarity only to the interaction of polynucleotides with single stranded binding proteins.

Acid Anhydride Hydrolases↗
PubMed2000

Passive Transport of Ionic Drugs through Membranes with pH-Dependent Fixed Charges.

We have studied both theoretically and experimentally the passive transport of ionic drugs through membranes with pH-dependent fixed charge. The system considered constitutes a simplified model for pH-controlled drug delivery through membranes of biochemical and pharmaceutical interest. The theoretical approach employed is based on the Nernst-Planck flux equations and all of the species present in the system (the neutral or ionic drug and the hydrogen and hydroxide ions) have been taken into account together with a Langmuir-type isotherm for the adsorption of the ionic drug onto the membrane surface. The membrane permeabilities of cationic, anionic, and neutral drugs through porous membranes with graft-polymerized weak polyelectrolytes have been measured as a function of the external pH. According to the nature of the grafted polyelectrolyte, the ionized membrane fixed groups can be negative or positive. For the amphoteric membrane, both fixed charge groups are present in the grafted chains. In all cases, the ionization state of the weak polyelectrolyte fixed groups changes with the local pH within the membrane. A comparison of the theoretical results with the experimental data allows one to explain qualitatively the changes of the membrane flux with the external pH and gives new physical insights into the transport problem. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

On the General Expression for the Electrophoretic Mobility of a Soft Particle.

Electrokinetic equations for electrophoresis of a soft particle (that is, a hard particle covered with a layer of polyelectrolytes) have been solved previously under the conditions that the net force acting on the soft particle as a whole (the particle core plus the polyelectrolyte layer) must be zero and that the electrical force acting on the polymer segment is balanced with a frictional force exerted by the liquid flow (J. Colloid Interface Sci. 163, 474 (1994)). In the present work we replaced the latter condition by the alternative and more appropriate condition that pressure is continuous at the boundary between the surface layer and the surrounding electrolyte solution to solve the electrokinetic equations and obtained the general mobility expression for the electrophoretic mobility of a spherical soft particle. It is found that the general mobility expression thus obtained reproduces all of the approximate mobility expressions derived previously and, in addition, that the continuous pressure condition leads to the correct limiting behavior of the electrophoretic mobility in the case where the frictional coefficient tends to zero (this behavior cannot be derived from the force balance condition for the polyelectrolyte layer). Copyright 2000 Academic Press.

Journal Article↗
PubMed1976

The interaction of leukocytes and their hydrolases with bacteria in vitro and in vivo: the modification of the bactericidal and bacteriolytic reactions by cationic and anionic macromolecular substances and by anti-inflammatory agents.

Acid hydrolases from extracts of human blood leucocytes lyse Staph.aureus, Staph.albus and Strep.faecalis in vitro. The leucocyte enzymes can be substituted by a lytic mixture which contains crude trypsin, lysolecithin, phospholipase C and lysozyme, which lyse other bacterial species, e.g. E.coli and Listeria which are resistant to leucocyte enzymes. Bacteriolysis by the lytic agents is strongly inhibited by the anionic polyelectrolytes, heparin, chondroitin sulphate, DNA, dextran sulphate and other sulphated mucopolysaccharides, by the cationic materials, histone, protamine sulphate, leucocyte cationic proteins and polylysine. Other strong inhibitors are trypsan blue and congo red, the phospholipids phosphatidyl serine and ethanolamine, gold thiomalate, extracts of coffee and tea and the anti-inflammatory agents, ultracorten-H, and ultracortenol. Bacteriolysis is also strongly inhibited by normal human serum and by synovial fluids from patients with a variety of joint diseases. The inhibitors in these body fluids are associated with the globulin fractions. Since mixtures of anionic and cationic polyelectrolytes, at equimolar concentrations, failed to inhibit bacteriolysis by leucocyte enzymes, it is postulated that a delicate balance between positively and negatively charged inhibitors control the degradation of cell wall components of bacteria in inflamed areas. Such bacterial components, induce 'storage type' granulomas. The possible role played by polyelectrolytes in the control of the inflammatory process induced by leucocyte hydrolases will be discussed.

Animals↗
PubMed1996

Characterization of hydrogels using luminescence spectroscopy.

In this contribution the literature relevant to characterization of polyelectrolytes, polyelectrolyte complexes and hydrogels using luminescence spectroscopy is reviewed. A brief introduction to the fundamentals of luminescence is followed by a description of the various types of spectroscopic studies which may be used to characterize hydrogels. In addition to experiments based upon the addition of a viscosity, temperature- or polarity-sensitive fluorescent probe to characterize the local environment, experiments and techniques based upon luminescence quenching, fluorescence polarization, phosphorescence depolarization and excimer fluorescence are discussed. This review succinctly describes the utility of luminescence spectroscopy in the characterization of hydrogel systems, with a focus on recent developments in the characterization of hydrogels and polyelectrolyte complexes.

Dansyl Compounds↗
PubMed2006

Clay and oxide destabilization induced by mixed alum/macromolecular flocculation aids.

The review points out typical differences and analogies of the bulk characteristics of aluminum ion complexed polyelectrolytes and of their adsorption behaviors when such systems were supplied to inorganic colloids such as oxides and clays. It reports some particular investigations that were carried out in aqueous media to determine (i) the nature of the interactions existing between clay or oxides, aluminum ions and polyelectrolytes and (ii) the effects on the interfacial characteristics and the colloid stability related to the relative concentrations of these different constituents. The investigations concerned the synthetic alumina/polyacrylic acid systems and the natural kaolinite/humic acid systems, as well as partly the mixed alumina/humic acid systems. Different adsorption features and destabilization kinetics were determined to develop within these systems. One of the main constraints of the investigation arose from the presence of three interacting components which developed amphoteric and amphipatic interactions, the latter being generated by the hydrophobic moieties induced by the aluminum ions/carboxylic acid groups ion-pairing. The investigations concerned the extent and the rate of transfer of hydrogen, aluminum ions and polyelectrolytes from the bulk solution to the solid surface. Electrical surface charge characteristics were expressed in terms of the zeta potential of the colloid/polymer complexes. The colloid stability of the systems was determined as a function of time at short and long terms. The variation as a function of time of the number and weight average masses was correlated with the variation with time of the zeta potential. All these systems were determined to reach the kinetic and thermodynamic equilibrium only slowly. Despite the fact that the supply of mixed coagulants provoked the initial aggregation and the subsequent fragmentation processes for both systems, the mechanisms responsible for the two processes were found to be different as revealed by comparatively investigating the synthetic and the natural systems. The fragmentation originated from the slow segregation process of positively and negatively charged groups for the natural kaolinite/humic acid systems, while the segregation process affected hydrophobic and hydrophilic moieties for the synthetic alumina/polyacrylic acid systems.

Journal Article↗