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At least 991 records · Page 55Linked to original sources
PubMed2006

Compression-inhibited pore formation of polyelectrolyte multilayers containing weak polyanions: a scanning force microscopy study.

Morphological changes of poly(acrylic acid)/poly(diallyldimethylammonium chloride) multilayers induced by low pH were investigated by scanning force microscopy. The weakened interaction between the charged polymer chains in the protonation process is believed to be the reason for this variation. Kinetic studies have shown that during protonation phase separation and dissociation of the multilayers took place successively. The compression of the multilayers, however, caused a transition of the multilayers from a rubbery state to a glassy state. As a result, the closely compacted multilayers lost their sensitivity to pH change. An increase of electrostatic and hydrophobic interactions, can decrease the free energy of the multilayers, and stabilize the films. By compression of the multilayers with a rubber stamp having geometric patterns, films with spatially localized pores were produced.

Journal Article↗
PubMed2004

Polyelectrolyte-modified short microchannel for cation separation.

Three alkali cations, potassium, sodium, and lithium, have been separated within 15 s in a 1 cm long polymer microchip. The separation microchannel is modified by a polycation, poly(allylammonium chloride), which makes the channel surfaces positively charged leading to a reversed electroosmotic flow (EOF) when compared to bare channels. Due to the decreased apparent mobility of the cations, the separation resolution is improved allowing the use of shorter channels.

Cations↗
PubMed1983

Setting of dental polyelectrolyte cements--viscosity studies of model systems.

In order to gain information on the setting of dental cements, the influence of Ca2+, Mg2+, Zn2+, and Al3+ ions on the viscosity of concentrated solutions of partly neutralized poly(carboxylic acids) has been measured. The increase in viscosity with increasing cation concentration was semi-quantitatively interpreted in terms of chain growth and branching due to intermolecular bridging of the carboxylate groups by the metal ions. The concentration of cation required to produce gelation was considerably greater than expected and may be due to the wastage of cations by the formation of intramolecular links. The incorporation of tartrate ion into the polyacid solution retarded the reaction between Al3+ and the polyacid and may explain some features of the setting of glass ionomer cements.

Aluminum↗
PubMed2003

Quantitative evaluation of bacteria adherent to polyelectrolyte HEMA-based hydrogels.

The use of adhesive poly(HEMA)-based hydrogels is standard practice in dental restorative procedures. Microorganisms, which potentially can cause oral pathologies, may colonize these polymers. In the present work, bacterial adhesion to polymers prepared with 2-hydroxyethyl methacrylate (HEMA) and to different molar ratios of 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) and/or to 2-methacryloyloxyethyl-tri-methyl-ammonium chloride (METAC) co-monomers were tested. A colorimetric assay system that utilizes the Microbo revelation medium (Microbo srl, Rome, Italy) for microbial counts is shown to be capable of counting the number of adherent bacterial cells without removing them from polymer surfaces. In conditions that mimic those present in the oral cavity, similar bacterial adhesion percentages on the same polymer were observed with the different bacteria belonging to both gram-positive and gram-negative genera, such as Streptococcus sobrinus and Streptococcus oralis (resident microorganisms in the oral cavity) and Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa (transient microorganisms in the oral cavity). It is determined that the physico-chemical characteristics of poly(HEMA)-based hydrogels are the major factors promoting bacterial adhesion, which increased with increasing water content in the swollen polymers, reaching maximal values on the cationic polymers.

Bacteria↗
PubMed2006

Effect of crosslinking on the elasticity of polyelectrolyte multilayer films measured by colloidal probe AFM.

A homemade colloidal probe atomic force microscope was used to perform nanoindentation with a spherical probe of 5 microm in diameter, at different approach velocities in order to extract the Young's modulus, E0, of poly(L-lysine)/hyaluronan (PLL/HA) films. This parameter is of prime importance to control cellular adhesion. The films were either kept in their native form or cross-linked with a mixture of 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC) and N-hydrosulfosuccinimide (sulfo-NHS), where the EDC concentration was varied from 1 up to 100 mg mL(-1) (approximately from 5 to 500 mM). A model based on Hertz mechanics was used to account for the interactions between film and probe. It is shown that the Young's modulus varies with the approach velocity for the native (PLL/HA) films, whereas for cross-linked ones, E0 is independent from the velocity over the whole range investigated. It is found that for native films, E0 takes a value of 3 kPa at low approach velocities, a velocity domain that should be relevant in cellular adhesion processes. The Young's modulus increases with the EDC concentration used to cross-link the films and levels off at a value of about 400 kPa for EDC concentrations exceeding 40 mg mL(-1). Thus, it is possible by crosslinking PLL/HA films to control their elastic properties with the aim to alter their behavior as to the cellular adhesion.

Cell Adhesion↗
PubMed1977

Effects of polyelectrolytes on drug transport II: permeation.

The permeation rate of salicylate across a dialysis membrane was studied in the presence of various types of carboxymethylcellulose. The presence of the polymer in the salicylate solution increased the permeation rate of salicylate. The data were analyzed with a diffusional model in which the viscosity and charge effects were evaluated separately.

Biological Transport↗