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PubMed2006

Boronate-containing copolymers: polyelectrolyte properties and sugar-specific interaction with agarose gel.

Copolymers of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with acryamide (AA), N,N-dimethylacrylamide (DMAA), and N-isopropylacrylamide (NIPAM) were found to adsorb on cross-linked agarose gel (Sepharose CL-6B) in the pH range from 7.5-9.2, due to specific boronate-sugar interactions. The molar percentages of phenylboronic acid (PBA) groups in the boronate-containing copolymers (BCCs), as estimated by 1H NMR spectroscopy, were 13, 10, and 16%, respectively, whereas the apparent ionization constants, the pKa values, of the copolymers were similar and equal to 9.0 +/- 0.2 at 20 degrees C. The copolymers adsorption capacities were in the range of 15-30 mg x ml(-1) gel (14-36 micromol pendant PBA ml(-1) gel) at pH 9.2 and decreased with decreasing pH value. The interaction of monomeric NAAPBA with Sepharose CL-6B was characterized by an equilibrium association constant of 53 +/- 17 M(-1), the chromatographic capacity factor k' = 1.8, and a total content of binding sites of 27 +/- 10 micromol x ml(-1) gel at pH 9.2. The weak reversible binding of monomeric NAAPBA and almost irreversible binding of NAAPBA copolymers to the gel at pH 9.2 suggested a multivalent character of the copolymer adsorption. At pH 7.5, the maximal adsorption capacity was displayed by the AA-NAAPBA copolymer (15 mg x ml(-1) gel). All the BCCs could be completely desorbed from the gel by 0.1 M fructose in aqueous buffered media with pH values from 7.5-9.2. The strong adsorption of AA-NAAPBA on agarose gel probably relates to the conformation of the copolymer in aqueous solution and provides opportunities for biomedical applications of the copolymer under physiological conditions. Multivalent, weak-affinity adsorption of BCCs to the agarose gel seems to be a tentative model for the copolymers' binding to oligo- and polysaccharides of cell membranes and mucosal surfaces.

Adsorption↗
PubMed1996

Effect of EO Chain Length of Dodecanol Ethoxylates (C12En) on the Complexation of C12En/SDS Mixed Micelles with an Oppositely Charged Polyelectrolyte

Turbidimetry, dynamic light scattering, and capillary electrophoresis were used to study the complexation of polydiallyldimethylammonium chloride (PDADMAC) with mixed micelles of sodium dodecyl sulfate (SDS) and dodecanol ethoxylates (C12En). The effect of EO chain length and its distribution was examined using various combinations of C12En (n = 4, 6, 8, 12). The results show that the onset of the complexation of PDADMAC with the mixed micelles is affected by the EO chain length of C12En: the mole fraction (Y) of SDS in the mixed micelle required to form the complex (Yc) increases with n. The effect of EO chain length on the onset of bulk phase separation shows the same trend. Although Yc varies with n, the electrophoretic mobility of mixed micelles with composition corresponding to Yc is independent of n. We propose that the effect of EO chain length has two aspects: (1) an increase in the average distance between bound polycation segments and the SDS sulfate groups, and (2) an increase in the distance between SDS head groups, which causes a decrease in the surface charge density (sigma) of the micelle. Therefore, the electrical potential at the mean locus of bound polymer segments, psi0, decreases with increasing n; in order for complexation to occur, this effect must be compensated for by a larger value of Y. Broader distributions of EO chain length lead to an increase in the range of Y over which the soluble complex is stable. We suggest that polycations initially bind to micelles which are rich in shorter EO chains and thus have higher "surface" potential, psi0. However, additional SDS may go preferentially into micelles rich in longer chains with lower psi0. This delays the formation of micelles which have sufficiently large psi0 to cause phase separation.

Journal Article↗
PubMed1996

Optimization of Long-Term Stability of Magnetic Fluids from Magnetite and Synthetic Polyelectrolytes

Nanometer-sized suspensions of magnetite (Fe3O4) stabilized with polymeric surfactants, principally poly(methacrylic acid) (PMAA), were prepared by precipitation or sonication and studied by a variety of techniques. The long-term stability of the ferrofluids made with PMAA was optimal at pH 7 (close to the measured isoelectric point of the magnetite, 5.9) and improved at all pH values with increasing surfactant concentration. With extended times of sonication the molecular weight and polydispersity of the PMAA decreased, although magnetite in the ferrofluid was not oxidized (X-ray). Particle diameters of 9-38 nm were measured by saturation magnetization, electron microscopy, and dynamic light scattering. Centrifugation at 8,000 rpm removed the magnetite from the suspensions together with roughly one molecule of PMAA for each magnetite particle in the fluid, with the average number increasing with higher concentrations and average molecular weights of the polymer.

Journal Article↗
PubMed1997

Effect of Nonadsorbing Polyelectrolytes on Colloidal Interactions in Aqueous Mixtures

The effect of adding a nonadsorbing charged polymer, sodium polystyrene sulfonate (SPSS), on the interaction energy profile between a 15 &mgr;m diameter polystyrene particle and a glass plate was measured using the optical technique of total internal reflection microscopy. A typical profile consisted of a repulsive barrier at large separations followed by a secondary well. Evidence of a longer-range tertiary well was also observed in salt-free solutions where the polymer molecules are rod-like. Addition of electrolyte causes a reduction in the depth of the tertiary well and produces oscillations at large separations. In addition, the stability of a solution of charged polystyrene particles in the presence of SPSS was measured using optical light scattering. Because of the electrostatic repulsion between the particles, the solution was stable against primary flocculation with no added polymer. However, because of long range attractive depletion forces, reversible secondary flocculation occurred into a local potential energy minimum at low SPSS concentrations (order 0.2 wt%). The polymer caused flocculation at a critical flocculation concentration (v *) which was found to decrease with increasing particle size. No restabilization of the latex dispersions was observed.

Journal Article↗
PubMed1998

Laterally Resolved Measurement of Interaction Forces between Surfaces That Are Partly Covered with Polyelectrolytes.

The adsorption of polycation poly(diallyldimethylammonium chloride), PDADMAC for short, on oxidized silicon wafers is investigated by direct force measurements using an atomic force microscope. It is shown that the electrostatic forces as well as the adhesive properties are significantly influenced by adsorbed PDADMAC. By using force mapping and monitoring the increased adhesion between the surfaces the adsorbed polymer can be two-dimensionally monitored on the surface. Different coverages of the polycation were investigated, which qualitatively agree well with results of XPS and electrokinetic measurements. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Binding of Photosurfactant (4-butyl-azobenzene-4'-oxyethyltrimethylammonium bromide) to Polyelectrolyte.

The binding of a photosurfactant, 4-butyl-azobenzene-4'-oxyethyltrimethyl ammonium bromide (BZTABr), to a linear polymer, sodium poly(2-acrylamide-2-methylpropane sulfonate) (PAMPS), has been studied by using a surfactant selective electrode. The photosurfactant undergoes a trans-cis transition on UV/vis irradiation. The binding behavior changes by varying the composition of the trans and cis forms in the solution. The ideal mixing-ideal cooperative binding model we had proposed previously for the binding of binary surfactants was applied to successfully predict the binding isotherms and the critical aggregation concentrations of the present systems. The binding of a trans-cis mixture of BZTABr to a polymer is analogous to the ideal mixed micelle formation. A sort of synergetic effect was found in the binding process. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Absorption of Polyelectrolytes on Colloidal Surfaces as Studied by Electrophoretic and Dynamic Light-Scattering Techniques.

zeta-Potential and the effective diameter of the colloidal spheres absorbed with the macro-cations and macro-anions are studied by the electrophoretic light-scattering and dynamic light-scattering measurements. Colloidal spheres used are monodispersed polystyrene (220 nm in diameter) and colloidal silica spheres (110 nm). Macro-ions used are sodium polyacrylate, sodium polymethylacrylate, sodium poly(styrene sulfonate), and poly-4-vinyl pyridines quaternized with ethyl bromide, n-butyl bromide, benzyl chloride, and 5% hexadecyl bromide and 95% benzyl chloride. Reversal of colloidal surface charges from negative to positive occurs abruptly above the critical concentration of macro-ions by the excess absorption of the macro-cations onto the anionic colloidal spheres, i.e., avalanche-type absorption. The effective diameter of colloidal spheres including the absorbed layers increases substantially by four- to tenfold. In the presence of large amount of macro-cations aggregation of colloidal spheres mediated by the layers of absorbed macro-cations may occur. Absorption also occurs on the anionic colloidal spheres in the presence of an excess amount of macro-anions by the dipole-dipole-type attractive interactions. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Importance of lateral and steric stabilization of polyelectrolyte gene delivery vectors for extended systemic circulation.

Gene therapy for systemic diseases requires intravenous administration, but existing vectors are not suitable for systemic delivery, often showing rapid elimination from the bloodstream that restricts potential transfection sites to "first-pass" organs. To develop long-circulating vectors, here we have compared polyplexes containing DNA and poly-L-lysine (PLL) or polyethylenimine (PEI), surface-modified with either monovalent polyethylene glycol (PEG) or multivalent copolymers of N-(2-hydroxypropyl)methacrylamide (PHPMA), correlating their biophysical properties with their distribution following intravenous injection. A key difference between the two types of coating is the introduction of lateral stabilization by surface attachment of multivalent PHPMA, in addition to the steric stabilization provided by both types of polymers. The alpha-half-life for bloodstream clearance of polycation/DNA polyplexes (typically <5 minutes in mice) could be extended using multivalent PHPMA coating to >90 minutes. We found that the dose administered, as well as the amount and molecular weight of the coating PHPMA, had important effects on circulation properties. Multivalent PHPMA coating allows, for the first time, considerably extended circulation time using polyplex systems-a prerequisite for systemic gene delivery.

Acrylamides↗
PubMed1979

Effect of leukocyte hydrolases on bacteria. XIV. Bacteriolytic effects of human sera, synovial fluids, and purulent exudates on Staphylococcus aureus and Streptococcus faecalis: modulation by Cohn's fraction II and by polyelectrolytes.

Normal sera and plasma, derived from humans, calves, rats, rabbits, horses, human synovial fluids, inflammatory exudates, and leukocyte extracts, when sufficiently diluted are highly bacteriolytic for Staph, aureus, Strep. faecalis, B. sutilis and to a variety of gram-negative rods. On the other hand, concentrated serum or the other body fluids are usually not bacteriolytic for these bacterial species. While the lysis of Staph, aureus and B. subtilis by diluted serum is not lysozyme dependent, lysis of Strep. faecalis is absolutely dependent on the concentration of lysozyme. The lytic factor in human serum is present in Cohn's fractions III, IV, and V. It is nondialyzable, resistant to heating for 75 degrees C and 20 min, and acts optimally at pH 5.0. Like leukocyte extracts, synovial fluids, and inflammatory exudates, it lyses only young staphylococci. The inability of concentrated serum to lyse Staph. aureus and Strep. faecalis is due to the presence in the gamma globulin fraction of a potent inhibitor, which can be partly removed by dilution of by adsorption upon the homologous bacteria. Lysis of the bacteria is also strongly inhibited by Cohn's fraction II (gamma globulin) by high-molecular-weight DNA, heparin, liquoid, and histone. The possible role played by serum globulin in the protection of bacteria against degradation by leukocyte is discussed.

Animals↗