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PubMed1998

Simulation of Particle Adsorption onto a Polymer-Coated Surface Using the Dissipative Particle Dynamics Method.

Dissipative particle dynamics (DPD) was originated as a tool for performing fluid dynamics simulations of complex fluids and among other things has been used to simulate dilute polymer solutions. This report describes a new application of the technique-modeling the adsorption of colloidal particles onto a polymer-coated surface. This type of simulation would be beyond the scope of molecular dynamics but is effectively modeled with DPD. The preliminary results of these investigations, presented here, show good agreement with what might be predicted theoretically. They show that the colloidal particles would be less likely to adsorb onto the surface as the size of the polymer relative to the particle is increased, or similarly as the density of the polymers is increased. They also show that particle adsorption is reduced when the polymer is well solvated. They demonstrate how particles that have agglomerated with each other find it more difficult to penetrate a polymer barrier because of their greater size. Further investigation is required to understand the effects of temperature. Copyright 1998 Academic Press.

Journal Article↗

PubMed2001

Study of the Second Order Transitions and Acid-Base Properties of Polymers Adsorbed on Oxides by Using Inverse Gas Chromatography at Infinite Dilution.

In Part I, we gave the details concerning inverse gas chromatography (IGC) at infinite dilution and the methods and models that will be used to characterize solid substrates. This technique proved to be an excellent technique to determine not only the glass transitions, but also beta-transition and liquid-liquid transitions of polymers adsorbed on solid substrates. In this second part, we used the IGC technique to determine the second order transitions of the systems' polymethyl methacrylate (PMMA)/SiO(2) and PMMA/Al(2)O(3), at various covered surface fractions and for various tacticities of the polymer. The maxima of the dispersive component of the surface energy gamma(s)(d) of our two systems, obtained by IGC at infinite dilution, indicated clearly the presence of transition temperatures (glass or local transitions). In general, we observed with PMMA three principal maxima that reflect the changes in motions leading to reorganization and rearrangement of the various groups or chain segments of the polymer. The change in the retention mechanism of the probes at the transition temperatures is attributed to an increased molecular mobility of the polymer segments, allowing for the penetration of the probes into the polymer layer. The study of the chemical physical properties of PMMA/SiO(2) and PMMA/Al(2)O(3) revealed an important difference in the acidic and basic behavior, in Lewis terms, of oxide covered by various concentrations of PMMA. This study also highlighted an important effect of the tacticity of the polymer on the acidic basic character of PMMA adsorbed on oxides. Copyright 2001 Academic Press.

Journal Article↗

PubMed1990

Drag-reducing polymers: a novel class of diuretic and natriuretic compounds.

Previous studies have demonstrated that Separan AP-30, a drag-reducing polymer, significantly decreased the formation of atherosclerotic plaques in rabbits fed a high-cholesterol diet. Furthermore, Separan AP-273, a polymer similar to but longer than Separan AP-30, markedly increased cardiac output in open-chest rats. Preliminary studies in our laboratory have described diuresis and natriuresis following the intravenous infusion of Separan AP-273. These studies did not determine whether this natriuresis was common to drag-reducing polymers or unique to Separan. In the present study the renal effects of two chemically dissimilar drag-reducing polymers of molecular lengths approaching approximately 100 microns were compared. Sprague-Dawley rats (250-300 g) were anesthetized (Nembutal) and a tracheostomy was performed. A baseline level of sodium and water excretion was established by the infusion of saline (0.097 ml/min, IV). Separan (0.004%), an anionic polyacrylamide; Polyox (0.4%), a poly(ethylene oxide); or mannitol (20%), an osmotic diuretic, was infused into the jugular vein at 0.0034 ml/min. Separan and Polyox both increased the excretion of sodium and water (p less than 0.05). At the doses tested, potassium excretion was unaltered in both groups. Separan, but not Polyox, produced a modest increase in blood pressure. Creatinine clearance was unaltered. At this infusion rate, only hypertonic concentrations of mannitol (20%) induced a similar effect. These results indicate that drag-reducing polymers may represent a novel class of potassium-sparing diuretic and natriuretic compounds. The ability of this class of polymers to decrease the formation of atherosclerotic plaques, increase blood flow, and produce a potassium-sparing natriuresis may be of practical clinical significance.

Acrylic Resins↗

PubMed1983

Cell culture on polymers prepared by radiation-induced polymerization of various glass-forming monomers.

The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth.

Animals↗

PubMed1997

Expression of a synthetic protein-based polymer (elastomer) gene in Aspergillus nidulans.

A gene for a synthetic protein-based polymer, G-(VPGVG)119-VPGV, coding for the EG-120mer (elastomer), was cloned into a fungal expression vector to allow constitutive expression of the polymer controlled by the gpdA (glyceraldehyde-3-phosphate dehydrogenase) promoter sequence of Aspergillus nidulans. Stable transformants of A. nidulans showed plasmid integration with varying copy number when analyzed by Southern-blot hybridization. Expression of the synthetic gene was demonstrated by Northern-blot hybridization. However, the translational efficiency for production of the polymer polypeptide was low, presumably because of certain codons in the polymer gene (CCG and GUA) that are rarely used by A. nidulans. Partial purification by reversible phase transition followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed the presence of polymer protein in a transformant that contained multiple copies of the polymer gene. This study represents the first attempt to express a synthetic gene (with no natural analog) in a fungus.

Aspergillus nidulans↗

PubMed1992

Repulsive interactions and mechanical stability of polymer-grafted lipid membranes.

Liposome membranes containing lipids with covalently attached poly(ethylene glycol) (PEG-lipid) are currently being developed as drug delivery systems. These, so called, 'Stealth' liposomes have a relatively long half life (approximately 1 day) in blood circulation and show an altered biodistribution in vivo. The extended lifetime appears to result from a steric stabilization of the liposome by the grafted polymer. In order to characterize the surface structures that promote steric stability in such polymer-grafted lipid bilayer systems, we have used X-ray diffraction to measure the structural organization and interbilayer repulsion for lipid/cholesterol (2:1) bilayers incorporating 4 mol% of a PEG-lipid in which the molecular weight of the PEG moiety was 1900 g/mol. At this concentration, applied pressure versus interbilayer distance relations showed that the grafted polymer moiety extended approximately 50 A from the lipid surface and gave rise to a strong, slowly decaying repulsive pressure between membranes that opposed their close approach. Also, the pressure vs. distance relations were only modestly altered by changing the ionic strength of the medium (1 mM NaCl and 100 mM NaCl). Therefore, even though the PEG-lipid headgroup bears a negative charge, the long range pressure cannot be due primarily to an electrostatic double layer pressure. Measurements of lipid bilayer elasticity using micropipet manipulation showed that PEG-lipid did not change the cohesive properties of lipid/cholesterol liposomes which was consistent with the X-ray structural data showing that the PEG-lipid did not change the normal structure of the bilayer interior. From these data we conclude that the repulsive barrier properties of lipid-grafted PEG polymer chains originate mainly from a steric pressure and that this simple polymer steric stabilization is the basis for the extended in vivo circulation times observed for polymer-grafted liposomes.

Electric Conductivity↗

PubMed1992

Transport of glucose polymer-derived glucose by rabbit jejunum.

Mechanisms for the assimilation of glucose polymers have been inferred from perfusion studies. To further define these mechanisms, the results of measurements of unidirectional glucose fluxes across short-circuited rabbit jejunal segments in vitro are reported. Glucose polymer-stimulated short-circuit current was similar to that of glucose [19 +/- 6.0 microA/cm2 (n = 7) and 26 +/- 5.7 microA/cm2 (n = 13), respectively] and was inhibited by both acarbose and phlorizin. Acarbose, an alpha-glucosidase inhibitor with no effects of glucose transport, was used to uncouple digestion from absorption. Mucosal-to-serosal flux of glucose polymer-derived glucose was lower than that of an equal weight/volume of glucose [124 +/- 62 nmol.h-1.cm-2 (n = 4) vs. 452 +/- 121 nmol.h-1.cm-2 (n = 6); P less than 0.05] and was inhibited by both phlorizin and acarbose. No glucose polymers were detected in the serosal bath solutions by thin-layer chromatography. It is concluded that glucose polymer-derived glucose is transported by a phlorizin-inhibitable process at a rate slower than that of free glucose, a finding that suggests that hydrolysis limits glucose polymer assimilation.

Analysis of Variance↗

PubMed1993

Application of polymer beta-cyclodextrin-treated fetal calf serum to in vitro antibody production.

In order to induce an optimal plaque-forming cell response to sheep red blood cells (anti-SRBC PFC response) in vitro, murine splenocytes have been cultured in RPMI 1640 medium containing 10% fetal calf serum (FCS). In this paper, we report that 10% intact FCS in such a conventional medium can be replaced by 2% modified FCS which has been exposed to insoluble polymer beta-cyclodextrin (CD). The most efficient procedure of treatment of FCS was an incubation of 1/50 diluted FCS with 20 mg/ml polymer beta-CD for 3.5 h at 20 degrees C. The PFC response supported by 2% polymer beta-CD-treated FCS, was the same as that obtained when mixing 10% FCS, and was completely dependent on the existence of antigen (SRBC) and enhanced by 2-mercaptoethanol. The time-course profiles of the PFC responses induced in both cultures were almost the same. The 2% polymer beta-CD-treated FCS-containing medium was also effective in inducing both a primary PFC response to the T cell-independent antigen (trinitrophenyl-lipopolysaccharide) and a polyclonal PFC response stimulated by lipopolysaccharide. Inactive FCS lots (so called deficient lots) also became fully supportive at 2% after treatment with polymer beta-CD. These results indicate that polymer beta-CD-treated FCS is not economical for supporting antibody production, but also useful for those experiments on isolation and analysis of factors derived from cultured lymphocytes.

Animals↗

PubMed1995

Patterns of prostaglandin E2 and leukotriene B4 production in inflammation induced by peptidoglycan-polysaccharide polymers of bacterial cell walls.

The changing levels of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) were compared over a period of 1 h to 15 days in two kinds of inflammatory responses induced in the rat air pouch by chemically similar polymers of peptidoglycan-polysaccharide (PG-PS) isolated from cell walls of group A streptococci. The smaller polymers (100 s, average mol. wt 5.3 x 10(6)) induced a more severe acute response over the first 24 h, whereas, from 3 to 15 days the larger polymers (10 p, average mol. wt 5 x 10(8)) induced greater chronic inflammation, as measured by pouch fluid volume, number of infiltrating cells and weight of granulation tissue. The most prominent difference between the two kinds of responses in the pattern of PGE2 and LTB4 were: (a) A shift between 1 to 6 h to much higher production of PGE2 in the exudate induced by large polymers. During this time the level of LTB4 also increased, but continued to be higher in the exudate induced by small polymers. (b) The sustained production of relatively high levels of LTB4 and PGE2 in the large polymer exudate at 15 days. Changes such as these indicate that this model is useful for analyzing mediators which regulate the evolution of acute into chronic inflammation.

Acute Disease↗

PubMed1994

Augmentation of host defense mechanisms against tumor by sperabillin polymers, new basic peptidyl biopolymers, in mice.

Sperabillin polymers, which have been shown recently to have antitumor activity, are new basic peptidyl polymers composed of a pseudo-peptide antibiotic, sperabillin A. The polymers, HP-2 (MW 9990), AP-2 (MW 20,100) and AB-2 (MW 35,000), were found to potently activate murine peritoneal macrophages. The phagocytosis-dependent respiratory burst and Fc gamma receptor expression of peritoneal macrophages from C57BL/6 mice were enhanced after in vitro cultivation with these polymers. When HP-2, a representative of these polymers, was intraperitoneally injected into mice, the number of peritoneal exudate cells increased and phagocytosis-dependent respiratory burst and class II (I-A) antigen expression of peritoneal macrophages were augmented. These macrophages showed strong inhibitory activity against the growth of murine tumor cell lines such as EL4 lymphoma and B16 melanoma. Nitrogen oxide, tumor necrosis factor (TNF) and interleukin 1 (IL-1) might be required for this inhibitory activity. Moreover, in mice treated with HP-2, splenocyte counts also increased and non-specific killer activity of the splenocytes was augmented. These results indicate that sperabillin polymers are new macrophage activators.

Adjuvants, Immunologic↗

PubMed2005

The use of mucoadhesive polymers in buccal drug delivery.

Buccal delivery of the desired drug using mucoadhesive polymers has been the subject of interest since the early 1980s. Advantages associated with buccal drug delivery have rendered this route of administration useful for a variety of drugs. This review highlights the use of mucoadhesive polymers in buccal drug delivery. Starting with a review of the oral mucosa, mechanism of drug permeation, and characteristics of the desired polymers, this article then proceeds to cover the theories behind the adhesion of bioadhesive polymers to the mucosal epithelium. Additionally, we focus on the new generation of mucoadhesive polymers such as thiolated polymers, followed by the recent mucoadhesive formulations for buccal drug delivery.

Adhesiveness↗

PubMed2006

Branched polyesters based on poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide): effects of polymer structure on cytotoxicity.

Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. For further optimization of this polymer class their cytotoxicity needs to be characterized establishing structure-toxicity relationships. Effects of type and degree of amine substitution as well as molecular weight on cytotoxicity were evaluated in L929 mouse fibroblasts using a MTT assay whereas interactions with cell membranes were quantified by LDH release and caspase (3/7)-activation. Finally, direct cell-polymer contact assays were conducted. Ungrafted amine-modified polymer backbone yielded IC(50) values in the range of 0.05-10mg/ml. Generally higher toxicities were observed with an increasing degree of amine substitution. Amine substituents could be ranked as diethylaminopropylamine (DEAPA)<diethylaminoethylamine (DEAEA)<dimethylaminopropylamine (DMAPA) but the degree of amine substitution was more dominant than the type of amine function. Membrane interactions seem to cause necrotic cell reactions in a dose-dependent manner for highly charged amine-poly(vinyl alcohol) (PVA) backbones. To attenuate cytotoxic effects DEAPA-PVA backbones were grafted with biodegradable PLGA side chains at molecular ratios of 1:10 and 1:20. Cytotoxicity of extracts of these polymers was significantly lower compared to ungrafted polymers possibly caused by shielding of polycationic backbone with hydrophobic PLGA side chains. P(33)-20, a polymer containing a sufficiently high degree of amine substitution could serve as a lead candidate for further investigations. In conclusion, structure-toxicity relationships could be established and shielding the polycationic backbone using PLGA side chains seems to be a promising strategy meriting further investigations.

Animals↗

PubMed2006

Hybridisation of surface-immobilised single-stranded oligonucleotides and polymer monitored by surface plasmon resonance.

We have investigated the hybridisation of thiol-modified single-stranded DNA embedded in a polyacrylamide layer through the technique of surface plasmon resonance (SPR). Kinetic studies were carried out by two different immobilisation methods: (a) SH-ssDNA was firstly attached on gold and the remaining free space was filled with polymer and (b) SH-ssDNA and the polymer was attached onto the surface from the same solution. The immobilisation methods were compared for various concentrations of SH-ssDNA. Hybridisation was dependent on both the immobilisation method and the concentration of the components. The highest hybridisation was obtained when SH-ssDNA and the polymer was immobilised from the same solution at low SH-ssDNA concentration or when high concentrations of oligos were spread onto the surface and the surface was post-treated with polymer. The target response corresponded to a surface coverage of 100+/-15 ng/cm2. The same surface coverage on hybridisation was also obtained when low concentration of SH-ssDNA and polymer was attached onto the surface from the same solution. The non-specific binding of sample DNA was very low at optimal concentrations due to the polymer and the hybridisation was linearly dependent on target concentration.

Acrylic Resins↗

PubMed2007

Optimizing the formulation of a myoglobin molecularly imprinted thin-film polymer--formed using a micro-contact imprinting method.

Thin-film myoglobin molecularly imprinted polymers have been fabricated using a micro-contact approach. By initially selecting the cross-linker on the basis of it having a minimal recognition for the template and using this as a starting point for functional monomer selection, we have produced myoglobin imprinted polymers with exceptionally high selectivities. The affinity of the polymers, for myoglobin, when prepared with a variety of different cross-linkers and no functional monomer was evaluated. Of these, tetraethylene glycol dimethacrylate (TEGDMA) exhibited the lowest affinity for the template species. Methyl methacrylate (MMA) was chosen as the functional monomer as when it was used in conjunction with TEGDMA, it exhibited maximum selectivity for the template compared to polymers made with other functional monomers. With a MMA to TEGDMA ratio of 1 to 3, the myoglobin molecularly imprinted polymer adsorbed 15.03+/-0.89 x 10(-11)mole/cm(2) of template from a 5.68 x 10(-7)M myoglobin solution, compared to 2.58+/-0.02 x 10(-11)mole/cm(2) for a polymer of similar composition, but formed in the absence of a template. Various washing conditions, using alkaline media to remove the template, were investigated. An extraction solvent comprising 2 wt.% SDS and 0.6 wt.% NaOH used at 80 degrees C for 30 min was shown to give the highest imprinting factor i.e. 5.83 with 72.82% myoglobin removal. The saturation kinetics of template binding to the thin-film MIP were examined and found to display a simple two-phase profile typical of non-cooperative binding. A Scatchard binding plot showed the dissociation constant (K(d)) for the specific binding phase to be 3.4 x 10(-7)M and the binding site capacity to be 7.24 x 10(-11)mole/cm(2). For the non-specific binding phase, K(d) was found to be 1.355 x 10(-5)M and the binding site capacity was determined as 9.62 x 10(-10)mole/cm(2). Selectivity experiments were carried out in both single protein and binary protein systems all using a total protein concentration of 5.68 x 10(-7)M. The molar ratio of adsorbed myoglobin to IgG, HSA and hemoglobin was found to 115.5, 230.9 and 2.5, respectively. While, in binary competition systems, myoglobin selectivity to IgG, HSA and hemoglobin was, respectively, 94.18, 98.21 and 61.09%. Rebinding in natural biological matrices, i.e. human serum or urine, showed the imprinted films to have significantly greater uptake than non-imprinted films. Re-binding in undiluted urine was found to be a facile process, with the imprinting factor, i.e. the ratio of MIP to NIP binding, being determined as 37.4.

Cross-Linking Reagents↗

PubMed2004

Formation of PCDDs and PCDFs during the combustion of polyvinylidene chloride and other polymers in the presence of HCl.

PVDC and three non-chlorinated polymers (PP, PET, and PA) were incinerated at 700-850 degrees C in a laboratory-scale quartz tubular furnace in the presence of HCl (ca. 500 ppm congruent with 0.8 mg/l), and the gas-phase formation of PCDD/Fs, their putative precursors and their homologue profiles were investigated. The addition of HCl had little or no apparent effect on the level of PCDD/Fs formation during PVDC combustion, and their homologue profiles were quite different from those of the three non-chlorinated polymers. With PVDC, O8CDD and particularly O8CDF were by far most prevalent, apparently as a result of the selective formation of the precursors. With each of the three non-chlorinated polymers, combustion at 800 degrees C or higher in the presence of HCl resulted in PCDD/Fs formation at levels equaling or exceeding those observed with PVDC. In trials made with one of them (PP) under the same conditions but using a large polymer sample (100 mg vs 20 mg in all other trials), the level of PCDD/Fs formation was far higher than with the smaller polymer samples, and thus demonstrated the importance of appropriate combustion conditions for polymer incineration.

Benzofurans↗

PubMed2005

Sublethal toxicity of two wastewater treatment polymers to lake trout fry (Salvelinus namaycush).

Lake trout fry (Salvelinus namaycush) were exposed in laboratory experiments to two wastewater treatment polymers, one anionic (MagnaFloc 156) and one cationic (MagnaFloc 368; Ciba Speciality Chemical), to determine if these chemicals which are used and discharged by mining operations in Canada's North pose a significant hazard to juvenile fishes. The cationic polymer was substantially more toxic to lake trout fry than the anionic polymer, with 96-h LC50 estimates of 2.08 and >600 mg/l, respectively. Separate 30-d exposure experiments yielded no observed and lowest observed effect concentrations, respectively, of 0.25 and 0.5mg/l for MagnaFloc 368, and 75 and 150 mg/l for MagnaFloc 156. In both cases, behavioural responses, especially startle response, were the most sensitive test endpoints. Histopathological assessment revealed that gill pathology appeared within a few days of exposure to both polymers, apparently as a result of localized hypoxia. Acute (4 d) effects included cloudy swelling of epithelial cells, increased gill vascularization, and thickening and shortening of the gill lamella. Chronic (30 d) polymer exposure produced only slightly greater pathological effects than acute exposure, with comparable responses observed only at >1.0mg/l MagnaFloc 368 and 150 mg/l MagnaFloc 156, suggesting that the fish displayed some level of both behavioural and physiological adaptation to the respiratory stress imposed by the two polymers.

Acrylic Resins↗

PubMed2005

Cell separation in microcanal coated with electrically charged phospholipid polymers.

To separate the cell population in whole blood using microcanal, the surface was covered with a polyion complex (PIC) composed of electrically charged phospholipid polymers. The phospholipids polymers were prepared by the polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate with 3-(methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit. The PIC was formed at the solid-liquid interface, that is, first, the cationic polymer was coated on the substrate and an aqueous solution containing the anionic polymer with different concentrations was applied to the polymer-coated substrate. The formation of the PIC was followed using a quartz crystal microbalance (QCM), and the PIC surfaces were analyzed by both zeta-potential measurement and X-ray photoelectron spectroscopic measurement. The surface electrical potential on the PIC was controllable from +40 to -40 mV by increasing the amount of the adsorbed anionic polymer. The PIC surface was prepared in microcanal. The surface electrical potential was sequentially changed. When the whole blood was introduced into the microcanal, the cells adhered on the positively charged surface, but could not adhere to the negatively charged surface. Even when the cells adhere to the surface, the morphology of cells was maintained. This is due to MPC units at the surface, which show a good biocompatibility. These results indicated that the change in the surface electrical potential will be a useful method to separate the cells from whole blood.

Blood↗

PubMed2005

Relaxation phenomena of hydrolyzed polyvinylamine molecules adsorbed at the silica/water interface II. Saturated heterogeneous polymer layers.

Surface area exclusion chromatography (SAEC) was employed to determine the individual relaxation of polymer molecules within a saturated heterogeneous layer composed of two polymers of different molecular characteristics. The investigations focused on three systems differing in molecular weight and/or hydrolysis grade. The molecular relaxation process was determined to be different within the heterogeneous layer when compared with the behavior of the same polymer in the homogeneous layer. The modifications in the relaxation process of a given polymer were imposed by the interfacial characteristics of the second polymer. Finally, in heterogeneous layers, the relative variation of the interfacial area of the two polymers is expressed in a single relationship.

Journal Article↗