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PubMed2004

Influence of the solvent composition on the aerosol synthesis of pharmaceutical polymer nanoparticles.

Spherical, Eudragit L100 polymer nanoparticles with and without a ketoprofen drug were prepared by a novel aerosol flow reactor method. In this method, the polymer solution is sprayed to form nanosized droplets followed by the evaporation of a solvent. A purpose of the work was to explore the effect of solvent, solvent mixture, and co-solute (ketoprofen) on the formation of polymer particle, and particularly on particle morphology. The solvents used, i.e. ethanol, THF, toluene, and water, were selected according to their vapor pressure and dissolution capability for the polymer. At the polymer concentration range from 0.2 to 1.5 g/l of the starting solution, the geometric number mean diameters (GMD) of the particles increased from 75 to 130 nm and from 65 to 100 nm from the solutions of ethanol and THF, respectively. Particle morphology was observed by a scanning electron microscope (SEM). Particles changed from collapsed to irregular via spherical shape in the course of the decreasing solubility of the polymer in the medium. This is critically dependent on the solvent evaporation rate as well as the solute solubility, i.e. fast evaporative removal of solvent results in collapsed particles whereas low solubility results in irregular particles. Interplay between the vapor pressure of the solvents and the polymer solubility in the medium made possible to prepare particles with more complicated structures such as shriveled and blistery structures. The particle morphology as detected by SEM did not change when 10 wt.% of ketoprofen was added to the precursor solution.

Aerosols↗

PubMed2005

Controlled delivery of testosterone from smart polymer solution based systems: in vitro evaluation.

The objective of this research is to develop injectable polymers solution based controlled release delivery systems for testosterone (TSN), using phase sensitive and thermosensitive polymers. A combination of poly(lactide) (PLA) and solvents mixture of benzyl benzoate (BB) and benzyl alcohol (BA) was used in the phase sensitive polymer delivery system. The effects of solvents system and drug loading on the in vitro TSN release were evaluated. In the case of thermosensitive polymer delivery systems, a series of low-molecular-weight poly(lactide-co-glycolide)-poly(ethylene glycol)-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers with varying ratio of lactide/glycolide (LA/GA, 2.0-3.5) were studied to control the release of TSN. The effects of varying block length of copolymers 1-4 on the in vitro TSN release were evaluated. Phosphate buffer saline (pH 7.4) containing 0.5% (w/v) Tween-80 was used as in vitro release medium. The amount of the released TSN was determined by an HPLC method. A controlled (zero-order) in vitro release of TSN was observed from both the phase sensitive and thermosensitive polymer delivery systems. Addition of BA (15%, v/v) in solvents system significantly (p<0.05) increased the release rate of TSN (0.33+/-0.01 mg/ml) from phase sensitive delivery system in comparison to solvent without BA (0.27+/-0.00 mg/day). Increasing drug loading also increased release rate. In the case of thermosensitive polymer delivery system, increasing the hydrophobic PLGA block length of copolymers significantly (p<0.05) decreased the release rate of TSN. It is evident from this study that the phase sensitive and thermosensitive polymers are suitable for developing prolong-release injectable implant delivery systems for TSN.

Drug Delivery Systems↗

PubMed2004

Influence of polymerization temperature on the molecular recognition of imprinted polymers.

This paper aimed at investigating the influence of polymerization temperature on the molecular recognition of molecularly imprinted polymers (MIPs) based on multiple non-covalent interactions. 3-l-Phenylalanylaminopyridine (3-l-PheNHPy) imprinted polymers were prepared using azobisnitriles as either thermal initiators or photoinitiators at various temperatures of 10, 40 and 60 degrees C, respectively. These polymers were subsequently evaluated in the high-performance liquid chromatographic (HPLC) mode for enantioselectivity. An unexpected result shows that polymer prepared at 40 degrees C has the highest enantioselectivity, but not the polymer prepared at lower temperature of 10 degrees C. Further, the effect of elution temperature and sample load on the selectivity of polymers was investigated in detail. In order to get a better understanding of the "exception", the influence of polymerization temperature on the polymerization extent and polymer morphology was studied by FT-IR spectrum test, cross-polarization magic angle spinning (CP-MAS) (13)NMR spectra experiment and pore analysis. Based on these results we attribute this "exception" to that there is a tradeoff between the extent of polymerization and stabilization of the template-functional monomer complexes. And an optimal polymerization temperature can be found for each combination of template and monomer.

Chromatography, High Pressure Liquid↗

PubMed2005

Viscosity behavior of silica suspensions flocculated by associating polymers.

Associating polymers are hydrophilic long-chain molecules containing a small number of hydrophobic groups, and act as flocculants in aqueous suspensions. The effects of associating and nonassociating polymers on viscosity behavior are studied for silica suspensions. Since flocculation is induced by polymer bridging, the viscosity behavior is converted from Newtonian to shear-thinning profiles. The additions of surfactant cause an increase in viscosity for suspensions prepared with associating polymer, whereas the flow behavior of suspensions with nonassociating polymer is not significantly influenced. In adsorption of associating polymers onto silica particles, the chain may adopt a conformation with a water-soluble backbone attached to the particle surfaces. The hydrophobic groups extending from the chains adsorbed onto different particles can form a micelle by association with surfactant. Therefore, the bridging flocculation is enhanced by surfactant. The cooperative micellar formation between associating polymer and surfactant is responsible for viscosity increase in suspensions.

Flocculation↗

PubMed2006

Visualization of TCE recovery mechanisms using surfactant-polymer solutions in a two-dimensional heterogeneous sand model.

This research focused on the optimization of TCE dissolution in a physical two-dimensional model providing a realistic representation of a heterogeneous granular aquifer. TCE was infiltrated in the sand pack where it resided both in pools and in zones of residual saturation. Surfactant was initially injected at low concentration to minimize TCE remobilization at first contact but was incrementally increased later during the experiment. Xanthan gum was added to the injected surfactant solution to optimize the sweep efficiency through the heterogeneous medium. Photographs and digital image analysis illustrated the interactions between TCE and the injected fluids. During the polymer flood, the effects of heterogeneities inside the sand pack were greatly reduced by the increased fluid viscosity and the shear-thinning effects of the polymer. The polymer also improved the contact between the TCE ganglia and the surfactant-polymer solution, thereby promoting dissolution. Surfactants interacted with the polymer reducing the overall viscosity of the solution. At first contact with a 0.5%(mass) surfactant solution, the TCE pools drained and some remobilization occurred. However, no TCE bank was formed and TCE did not penetrate into any previously uncontaminated areas. As a result, TCE surface area was increased. Subsequent surfactant floods at higher surfactant concentrations did not trigger more remobilization. TCE was mainly dissolved by the solution with the highest surfactant concentration. Plugging from bacterial growth or microgel formation associated to the polymer at the inflow screen prevented the full completion of the experiment. However, more than 90% of TCE was recovered with the circulation of less than 6 pore volumes of surfactant-polymer solution.

Electric Conductivity↗

PubMed2004

Effect of glycerol-L-lactide coating polymer on bone ingrowth of bFGF-coated hydroxyapatite implants.

Basic fibroblast growth factor (bFGF)-coated hydroxyapatite (HA) cylinders showed good bony incorporation in a previously conducted animal study. However, some cylinders exhibited focal inhomogeneous bone ingrowth. The purpose of the current study was to test whether glycerol-L-lactide polymer coating could improve release properties and bone incorporation of bFGF-coated HA implants. bFGF-coated HA cylinders with or without coating polymer were investigated for in vitro release of bFGF by an immuno-ligand-assay and also for bone ingrowth in miniature pigs after 42 and 84 days. Release from bFGF polymer composites was lower for the first 3 days compared to the other group but was more homogenous and detectable amounts were still found after 20 days. There was significant delay in bone ingrowth of the polymer implants in which even after 84 days bone ingrowth was not completed, whereas in the other group incorporation after 42 days occurred. Detailed histology revealed filling of the HA pores with the polymer, making ingrowth of the surrounding host bone impossible. Only after 84 days starting resorption of the polymer accompanied by bone ingrowth was found. The current study showed that glycerol-L-lactide is not suitable for coating of HA implants due to polymer induced "locking" of HA pores.

Animals↗

PubMed2006

New polymer-supported ion-complexing agents: design, preparation and metal ion affinities of immobilized ligands.

Polymer-supported reagents are comprised of crosslinked polymer networks that have been modified with ligands capable of selective metal ion complexation. Applications of these polymers are in environmental remediation, ion chromatography, sensor technology, and hydrometallurgy. Bifunctional polymers with diphosphonate/sulfonate ligands have a high selectivity for actinide ions. The distribution coefficient for the uranyl ion from 1 M nitric acid is 70,000, compared to 900 for the monophosphonate/sulfonate polymer and 200 for the sulfonic acid ion-exchange resin. A bifunctional trihexyl/triethylammonium polymer has a high affinity and selectivity for pertechnetate and perchlorate anions from groundwater. In one example, its distribution coefficient for perchlorate ions in the presence of competing anions is 3,300,000, compared to 203,180 for a commercially available anion-exchange resin. Polystyrene modified with N-methyl-D-glucamine ligands is capable of selectively complexing arsenate from groundwater. It complexes 99% of the arsenate present in a solution of 100 mg/L arsenate with 560 mg/L sulfate ions. Its selectivity is retained even in the presence of 400 mg/L phosphate. There is no affinity for arsenate above pH 9, allowing for the polymer to be regenerated with moderate alkali solution. In studies aimed at developing a Hg(II)-selective resin, simple amine resins were found to have a high Hg(II) affinity and that affinity is dependent upon the solution pH and the counterion.

Arsenic↗

PubMed2005

Sequential polymer dosing for effective dewatering of ATAD sludges.

Dewatering problems associated with the sludge from autothermal thermophilic aerobic digestion (ATAD) of sludge, result in large chemical conditioning costs for effective dewatering. A variety of chemical conditioners were used to improve dewatering, but none of them were able to dewater the sludge as desired at acceptable conditioning doses. It was found that during the digestion process, chemical precipitation of divalent cations occurred. Some of the ATAD sludge colloids were found to have a positive zeta potential and these were thought to be the precipitated divalent cations. Sequential polymer dosing using either iron or cationic polymer, followed by anionic polymer, was found to improve dewatering. The use of anionic polymer is essential and allows the use of smaller amounts of iron or cationic polymer for effective dewatering. The use of the less expensive anionic polymer along with cationic polymers has the potential to make the use of the ATAD process more economical.

Alum Compounds↗

PubMed2006

Enzymatic extraction of activated sludge extracellular polymers and implications on bioflocculation.

This study examines enzyme hydrolysis, a mild, effective, but a rarely used method of extracellular polymer extraction, in removing polymers from mixed culture activated sludge flocs. Two carbohydrate specific enzymes (alpha-amylase and cellulase) and a protein specific enzyme (proteinase) are used during the study. First, the kinetic aspect is investigated, then enzyme dose optimization is carried out on laboratory grown activated sludge samples cultured at solids retention times (SRT) of 4 and 20 days. A more commonly used cation exchange resin (CER) extraction technique is also employed for comparison purposes. Results indicate that the extraction of extracellular polymers by enzymes is a rather quick process reaching equilibrium within only a few hours. As the doses of enzymes are increased, the extracted polymer quantities increase up to a certain dose, beyond which not much extraction is observed. The method does not cause any significant cell lysis as measured by the viable cell counts. Carbohydrate-hydrolyzing enzymes extract small amount of proteins along with the carbohydrates and protein-hydrolyzing enzyme extracts some carbohydrates together with the proteins, indicating that proteins and carbohydrates exist bound to each other in the extracellular polymer network of sludge. Enzyme extraction generally gives a lower estimate of polymers compared to the CER method, but correctly detects the trends in the polymer quantity.

Cellulase↗

PubMed1999

Contaminant transfer during the coextrusion of tri-layer polymer films with a recycled layer. Effect of this transfer on the time of protection of the food.

Reusing old polymer packages as new food packages necessitates the coextrusion of tri-layer polymers, the old polymer being located between two virgin polymer layers. As it takes some time for the contaminant initially located in the old polymer, the virgin polymer layer acts upon the food pollution as a functional barrier. With the coextrusion process, the polymer layers are heated up to a high temperature and let cool down in air. During this coextrusion stage, the contaminant diffuses through the package at a fast rate over a short period of time. Then the time of protection of the functional barrier is significantly reduced. The process of the contaminant transfer is especially studied either during the coextrusion stage of the film or in the package-food system at room temperature.

Food Contamination↗

PubMed2002

Effects of carbohydrate polymers applicable in saliva substitutes on the anti-Candida activity of a histatin-derived peptide.

The effects of polymers applicable in saliva substitutes on the anti-Candida activity of the cationic antimicrobial peptide dhvar1 were investigated. Dhvar1 is a derivative of the 14 C-terminal amino acids of histatin 5. The effects of the following polymers were tested: uncharged hydroxyethylcellulose (HEC), negatively charged xanthan (XG) and three types of negatively charged carboxymethylcellulose (CMC) of identical mass but different degrees of carboxylic acid-group substitution (DS). The effects were tested at pH 4.0, 7.0 and 8.5 in a killing assay. HEC had no effect at any pH tested; XG and the three types of CMC caused a decrease in activity at increasing concentrations. Within the CMC group, inhibition increased slightly with increasing DS. These results suggest that the reduction in activity associated with these polymers is the result of electrostatic interaction between the positively charged peptides and the negatively charged polymers. In the absence of polymers, no effect of pH was found on the activity of dhvar1. In the presence of the charged polymers XG and CMC, lowering the pH from 7.0 to 4.0 resulted in a decrease of dhvar1 activity. It was concluded that, with respect to the retention of activity, HEC is the most appropriate polymer for use in combination with dhvar1. However, for use in saliva substitutes XG seems more suitable because of its rheological properties. If XG or CMC are to be used, their reductive effect on the anti-Candida activity of dhvar1 should be compensated for by increasing the peptide dose.

Antifungal Agents↗

PubMed1999

Temperature-controlled interaction of thermosensitive polymer-modified cationic liposomes with negatively charged phospholipid membranes.

To obtain cationic liposomes of which affinity to negatively charged membranes can be controlled by temperature, cationic liposomes consisting of 3beta-[N-(N', N'-dimethylaminoethane)carbamoyl]cholesterol and dioleoylphosphatidylethanolamine were modified with poly(N-acryloylpyrrolidine), which is a thermosensitive polymer exhibiting a lower critical solution temperature (LCST) at ca. 52 degrees C. The unmodified cationic liposomes did not change its zeta potential between 20-60 degrees C. The polymer-modified cationic liposomes revealed much lower zeta potential values below the LCST of the polymer than the unmodified cationic liposomes. However, their zeta potential increased significantly above this temperature. The unmodified cationic liposomes formed aggregates and fused intensively with anionic liposomes consisting of egg yolk phosphatidylcholine and phosphatidic acid in the region of 20-60 degrees C, due to the electrostatic interaction. In contrast, aggregation and fusion of the polymer-modified cationic liposomes with the anionic liposomes were strongly suppressed below the LCST. However, these interactions were enhanced remarkably above the LCST. In addition, the polymer-modified cationic liposomes did not cause leakage of calcein from the anionic liposomes below the LCST, but promoted the leakage above this temperature as the unmodified cationic liposomes did. Temperature-induced conformational change of the polymer chains from a hydrated coil to a dehydrated globule might affect the affinity of the polymer-modified cationic liposomes to the anionic liposomes.

Anions↗

PubMed2004

Charged polymers modulate retrovirus transduction via membrane charge neutralization and virus aggregation.

The specific mechanisms of charged polymer modulation of retrovirus transduction were analyzed by characterizing their effects on virus transport and adsorption. From a standard colloidal perspective two mechanisms, charge shielding and virus aggregation, can potentially account for the experimentally observed changes in adsorption behavior and biophysical parameters due to charged polymers. Experimental testing revealed that both mechanisms could be at work depending on the characteristics of the cationic polymer. All cationic polymers enhanced adsorption and transduction via charge shielding; however, only polymers greater than 15 kDa in size were capable of enhancing these processes via the virus aggregation mechanism, explaining the higher efficiency enhancement of the high molecular weight molecules. The role of anionic polymers was also characterized and they were found to inhibit transduction via sequestration of cationic polymers, thereby preventing charge shielding and virus aggregation. Taken together, these findings suggest the basis for a revised physical model of virus transport that incorporates electrostatic interactions through both virus-cell repulsive and attractive interactions, as well as the aggregation state of the virus.

Animals↗

PubMed1993

Probing alamethicin channels with water-soluble polymers. Size-modulated osmotic action.

Contrary to expectations based on heightened solution viscosity, alamethicin channels appear to speed up in the presence of water soluble polyethylene glycols (PEGs) and dextrans. Specifically, added polymers reduce the probabilities of transition to higher-conductance states but do not change channel lifetimes. They thereby shorten the duration of current "bursts." These modified probabilities and kinetics reveal the action of polymer osmotic stress to suppress channel formation. The osmotic action of large, fully excluded polymers shows that some 3,000 A3 of water are taken up by the channel from the solution upon each transition to an adjacent higher-conductance state. The partial osmotic action of incompletely excluded polymers reveals the extent of exclusion for different-size polymers. The partial exclusion thus measured agrees remarkably well with estimates using data on reduction of single-channel conductance by current-impeding polymers. One can relate the degree of each polymer's exclusion to its size and to the radius of the channel pore.

Alamethicin↗

PubMed2004

Assessment of the aquatic and terrestrial toxicity of five biodegradable polymers.

Radiofrequency countermeasures (i.e., chaff) may be released by fighter jets during tactical countermeasures training. Chaff cartridges, pistons, and endcaps (i.e., chaff dispenser materials), all currently made of styrene, are also released into the environment. Accumulation of chaff dispenser materials in the environment is a concern of the Department of Defense. The US Navy is exploring the possibility of constructing degradable chaff dispenser components made of biodegradable polymers. Five polymers are being considered. Degradability and toxicity tests are two of several criteria being used to evaluate various available biodegradable options. Dissolution products from four of five polymers being considered were toxic to aquatic organisms with LC50s/LOELs ranging between 1.24 and 731.30 mg total organic concentration/L. Supernatant from dissolving a 90:10 polyester amide/polyvinyl alcohol copolymer in water for 24h inhibited shoot growth of Brassica rappa and Lepidium sativum. Since our results were obtained using fractions of saturated degradable polymer solutions (1 or 10 g/L), we conclude that the tested degradable polymers were of low toxicity to the seven aquatic organisms and two terrestrial plant species used in our assays. However, our characterization of the toxicity of these degradable polymers may not be applicable to all species or environmental situations. Information gained from these studies will be used for making decisions on which polymers should be used in the engineering of environmentally friendly chaff dispenser cartridges, pistons, and endcaps.

Aircraft↗

PubMed1994

The protective effects of polymers in the cryopreservation of human and mouse zonae pellucidae and embryos.

OBJECTIVES: To evaluate the occurrence of injury due to physical factors in embryo cryopreservation and the effect of the polymers dextran, polyvinylpyrrolidone (PVP), and Ficoll on this mechanical damage. DESIGN: Damage to the zona pellucida (ZP) observed after cryopreservation was taken as indication of cryoinjury caused exclusively by physical factors. Human and mouse ZPs from oocytes remaining unfertilized after previous IVF attempts and mouse two-cell embryos were frozen in the presence of different polymers. After thawing, they were checked carefully for signs of physical damage (cracks). A possible toxicity of the use of the polymers in cryoprotection was evaluated by development to the blastocyst stage of mouse two-cell embryos that survived the freezing and thawing process. RESULTS: Incidences of damaged ZPs in groups of human and mouse ZPs and two-cell embryos frozen without polymers were found to vary between 20% and 29%. The use of any of the tested polymers resulted in significantly lower incidences of damaged ZPs (0% to 15%). Damage to the ZP after freezing and thawing in mouse embryos was accompanied by low survival rates of the embryo itself. Of mouse embryos that survived the cryopreservation process, blastocyst formation was not significantly different in groups frozen without polymer (80%) or in the presence of either dextran (90%) or Ficoll (82%); however, embryos frozen in the presence of PVP showed low blastocyst formation (12%). CONCLUSIONS: Polymers can protect embryos against cryoinjury by avoiding mechanical strain occurring during cryopreservation. Polyvinylpyrrolidine is toxic to mouse two-cell embryos when present during freezing and thawing.

Animals↗

PubMed2001

Synthesis and evaluation of molecularly imprinted polymers for extracting hydrolysis products of organophosphate flame retardants.

A molecularly imprinted polymer (MIP) that selectively retains diphenyl phosphate was prepared using a structural analogue, ditolyl phosphate, as a template. Diphenyl phosphate is a degradation product of the flame retardant additive, triphenyl phosphate. The latter has been shown to be a common airborne contaminant in indoor environments and to be emitted from various goods such as video display units. Triphenyl phosphate induces several documented biological responses, including allergenic effects. Two different polymers, one prepared from methacrylic acid and the other from 2-vinylpyridine (2-Vpy), were investigated for their ability to recognise diphenyl phosphate. The polymers were used in solid-phase extraction cartridges (MISPE) and evaluated by comparing their recovery and breakthrough parameters with those of corresponding non-imprinted polymers (NIPs). The polymer made from the basic monomer showed the most selective recognition to the acidic analyte. Diphenyl phosphate was adsorbed to the basic MIP (2-Vpy-MIP) when methanol was used as mobile phase, and approximately 80% of the analyte was recovered when eluted from this polymer using a mixture of methanol and trifluoroacetic acid. There was a clear difference in the retention strengths of 2-Vpy-MIP and the corresponding 2-Vpy-NIP. The selectivity of the investigated 2-Vpy-MIP polymer towards a structural analogue of diphenyl phosphate, di(2-ethylhexyl) phosphate was also assessed. This compound was less strongly retained using the same experimental conditions. The results indicate that the prepared 2Vpy-MIP strongly recognises diphenyl phosphate due to the imprinting effect. This interaction probably arises mostly from an ionic interaction between the basic monomers and the acidic analyte. An LC-electrospray ionisation multiple MS method, using negative ion detection and ion-pair chromatography, was developed for separation and quantification of the strongly acidic dialkylated phosphate esters. The instrumental limit of detection was below 50 pg for all investigated compounds and the MS method was shown to be linear in the investigated range of 0.05-85 ng.

Chromatography, Liquid↗

PubMed2002

Solvent effect on protein binding by polymer brush grafted onto porous membranes.

An epoxy-group-containing polymer chain was grafted onto the hollow-fiber form of a porous polyethylene membrane by the immersion of the electron beam-irradiated trunk polymer in glycidyl methacrylate diluted with methanol and 1-butanol. The epoxy group density ranged from 8.5 to 13.4 mol per kg of the trunk polymer. Subsequently, the epoxy groups produced were converted into sulfonic acid and diethylamino groups. The density of -SOH and -N(C2H5), groups was 0.40 and 2.2 mol per kg of the product. respectively. The polymer brush, defined as a polymer chain extending from the surface of a pore toward the interior of the pore, was evaluated from the determination of an equilibrium binding capacity of hen egg lysozyme (HEL) and bovine serum albumin (BSA). The polymer brush prepared in 1-butanol was found to be longer than that prepared in methanol from the determinations of liquid permeability and protein adsorptivity. The proteins were bound to the polymer brush prepared in 1-butanol, followed by the functionalization, at higher degrees of multilayer binding: about 30 for HEL and 6 for BSA.

Membranes, Artificial↗