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PubMed2000

An anionic siloxane polymer as a pseudostationary phase for electrokinetic chromatography.

A novel polymeric pseudostationary phase for electrokinetic chromatography is introduced and characterized. Siloxane polymers are of interest for this application because of the range of chemistries that could be developed based on these backbones, and because successful development of siloxane polymers would make it possible to employ much of the stationary phase chemistry developed in the past thirty years. A commercially available water-soluble siloxane with a hydroxy-terminated alkyl group was converted to the sulfate derivative. This siloxane polymer is water-soluble, effectively eliminating this limitation associated with siloxane polymers. When employed as a pseudostationary phase, this compound provided rapid, efficient, and selective separations. The electrophoretic mobility of the polymer was less than sodium dodecyl sulfate (SDS) and poly(sodium 10-undecenylsulfate), providing a compressed migration time range, which is the main limiting factor for this polymer. The chemical selectivity of the siloxane sulfate was somewhat different than SDS micelles. The siloxane was employed in buffers modified with a large amount of acetonitrile to separate a number of polynuclear aromatic hydrocarbons. The addition of acetonitrile caused an apparent discontinuity in the electrophoretic mobility of the polymer, which may indicate a change in the structure with increasing organic solvent content.

Buffers↗

PubMedDate not supplied

Molecularly imprinted polymer for monocrotophos and its binding characteristics for organophosphorus pesticides.

In this study, molecular imprinting was used to develop a method based on noncovalent interaction for the synthesis of a monocrotophos-specific polymer. The selective binding characteristics of the template polymer were evaluated by 1H NMR study. The result was consistent with the existence of multi-molecular complexes formed by hydrogen-bonding interactions. Batch rebinding studies in acetonitrile were undertaken to quantitatively evaluate the affinity of the polymer for monocrotophos. The experimental binding isotherms were fitted to the Freundlich isotherm and the total number of binding sites of the polymer can be calculated to be 4.046 micromol g(-1). The induced affinity and selectivity by imprinting were examined chromatographically. The polymer gave more than 15 times longer retention for monocrotophos than the nonimprinted polymer with the same chemical composition. Other organophosphorus pesticides under study were eluted close to the void volume on the polymer column.

Environmental Monitoring↗

PubMed1979

Idiotypic analysis of antibodies against the terpolymer L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT). IV. Induction of CGAT idiotype following immunization with various synthetic polymers containing glutamic acid and tyrosine.

The immune responses of all inbred strains of mice specific to the synthetic terpolymer poly(LGlu60LAla30LTyr10), referred to as GAT10, are characterized by the presence of anti-GAT antibodies which share a common (CGAT) idiotype. In this report, we describe the ability of the synthetic polymers, LGlu33LAla33LTyr33, LGlu51-LAla34LTyr15 and poly-L(Tyr, Glu)-DLAla--LLys [(T,G)-A--L] to induce antibodies with CGAT idiotypic specificities. All of these polymers contain "GT"-related determinants. Following immunization with these polymers, antisera from responder mice bind the corresponding 125I-labeled antigen and 125I-labeled poly(LGlu50LTyr50) or GAT10. These antisera shared the CGAT idiotype which is associated with the antibody fraction with binding specificity for GAT10. Collectively, the present results indicate that GT-related determinants are required for the induction of the CGAT idiotype. Moreover, since the immune responses to these synthetic polymers are under distinct H-2-linked immune response (Ir) gene control, a mouse strain can be nonresponder to one polymer and responder to another; in this case, only the latter polymer induces CGAT idiotype. Thus, although the immune responses of inbred strains of mice to different polymers are under distinct Ir gene control, the antibody responses can be idiotypically related.

Animals↗

PubMed1995

The use of coated and uncoated capillaries for the electrophoretic separation of DNA in dilute polymer solutions.

We show that both uncoated and polyacrylamide-coated capillaries provide separation of large DNA restriction fragments (2.0-23.1 kbp) by capillary electrophoresis in dilute cellulosic polymer solutions. Uncoated capillaries, however, provide significantly better resolution of DNA fragments, particularly when ultra-dilute polymer solutions are used. This is because electroosmotic flow in uncoated capillaries increases the residence time of DNA in the capillary, without significantly contributing to band-broadening. At a given field strength and polymer concentration in the buffer, the electrophoretic mobilities of DNA restriction fragments in coated capillaries are virtually identical to those previously measured in uncoated capillaries. It is concluded that the fused silica surface of the capillary does not play a significant role in the mechanism of DNA separation by capillary electrophoresis in uncrosslinked polymer solutions. Thus, the separation of large DNA which has been observed to occur in ultra-dilute polymer solutions arises primarily from entanglement interactions between the cellulosic polymers and DNA restriction fragments which occur within the bulk of the polymer solution.

Acrylic Resins↗

PubMed1990

Postadsorptive transitions in fibrinogen: influence of polymer properties.

Changes in the fibrinogen molecule after its adsorption to biomaterials may be important in determining blood compatibility. Previously, postadsorptive transitions were detected by measuring the elutability of adsorbed proteins with surfactant solutions. The elutability decreased with increased residence time, suggesting that protein-surface interactions increased with residence time. In this study, we have examined the effects of polymer structure and composition, chain mobility, and hydrophobicity on the postadsorptive transitions of fibrinogen. Glassy, rigid polymers showed high fibrinogen adsorption, regardless of whether the polymer was hydrophilic or hydrophobic. However, the binding strength (as measured by elutability) was much lower on hydrophilic polymers and oxygen-containing hydrophobic polymers. Short-term transitions, requiring 2 h or less after adsorption, were observed only on hydrophobic polymers that contained no oxygen. More gradual transitions were observed on hydrophobic polymers containing oxygen, but only after a lag time of 1-4 h.

Adsorption↗

PubMed2003

Synthesis and characterization of a novel polymer-ceramic system for biodegradable composite applications.

The objective of this study was to develop a biodegradable polymer resin that could be used for the fabrication of an interpenetrating phase composite (IPC) made of porous calcium polyphosphate (CPP) and an organic polymer resin. The resin was synthesized from a polycarbonate-based divinyl oligomer and monomers containing ionic groups. The physical and chemical properties of the polymer resin and polycarbonate-based divinyl oligomer were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, and swelling studies. The in vitro degradation of the polymer resins was assessed using cholesterol esterase in a buffer solution at 37 degrees C for 3 weeks. Scanning electron microscopy of the degraded samples indicated that the hydrolysis of the resin was catalyzed by the enzyme. The relative interfacial shear strength between the polymer resin and the CPP ceramic was studied using a microbond test. The addition of ionic groups into the polymer resin chains appeared to improve the chemical bonding between the polymer and the CPP. Preliminary mechanical properties of the IPC were investigated by determining bending strength using a three point bending test. The data showed a sevenfold increase in strength over that of the monolithic CPP, and the addition of more ionic groups into the resin led to a higher bending strength for the newly formed CPP/polycarbonate resin system. Sample cross sections of the IPC examined using scanning electron microscopy suggested that the resin had infiltrated almost all of the pores of the CPP. The results of this study indicate that the IPC could potentially be used for fabricating novel biodegradable load-bearing implants.

Biocompatible Materials↗

PubMed2003

Polymer design for corneal epithelial tissue adhesion: pore density.

A porous polymer is required to sustain corneal epithelial tissue on the anterior surface of an implantable contact lens (corneal onlay). Porosity creates topography on the polymer surface and, if defined, this can be manipulated to elicit a particular tissue response. Previous work identified pores of 100-nm diameter to be the critical size of a discontinuity in a polymer surface to facilitate the migration, stratification, and sustained adhesion of corneal epithelial tissue. Now we address the issue of pore density. Corneal epithelial tissue was grown for 21 days on nonporous polycarbonate and polycarbonate track-etched with pores 100-nm diameter with pore densities ranging from 0.27 and 14.4% of the total polymer surface area. Histology was used to score epithelial structure, and electron microscopy was used to quantitate the formation of adhesive structures (basal lamina and hemidesmosomes) at the tissue-polymer interface. Data showed that epithelial tissue stratified and epithelial adhesive structures formed on polycarbonate surfaces with pore densities between 0.52 and 14.4% inclusive. This means that epithelial tissue can be maintained on a polymer where up to 14.4% of the surface is dedicated to small discontinuities in the form of pores 100-nm diameter. These figures can be used to specify the design of a polymer for applications requiring epithelial cover.

Animals↗

PubMed2004

Temperature-sensitive polymer-conjugated IFN-gamma induces the expression of IDO mRNA and activity by fibroblasts populated in collagen gel (FPCG).

Indoleamine 2,3-dioxygenase (IDO) is an intracellular tryptophan-catabolizing enzyme possessing various immunosuppressive properties. Here, we report the use of this enzyme to suppress the proliferation of peripheral blood mononuclear cells (PBMC) co-cultured with IDO-expressing fibroblasts of an allogeneic skin substitute in vitro. Fetal foreskin fibroblasts populated within collagen gel (FPCG) were treated with interferon-gamma (IFN-gamma) conjugated with a temperature-sensitive polymer to induce the expression of IDO mRNA and protein. SDS-PAGE showed successful conjugation of IFN-gamma with the temperature-sensitive polymer. Expression of IDO mRNA was evaluated by Northern analysis. IDO enzyme activity was evaluated by the measurement of kynurenine levels. The results of Northern blot analysis showed an induction of IDO mRNA expression when treated with polymer-conjugated IFN-gamma. Kynurenine levels, as a measure of IDO bioactivity, were significantly higher in IFN-gamma-treated fibroblasts than in controls (P < 0.001). In a lasting effect experiment, the expression of IDO mRNA in FPCG treated with polymer-conjugated IFN-gamma was significantly longer than in those treated with free (non-conjugated) IFN-gamma (P < 0.001). IFN-gamma radiolabeling showed a prolonged retention of IFN-gamma within collagen gel in its polymer-conjugated form, compared to its free form. Presence of IDO protein in FPCG was demonstrated by Western analysis even 16 days after removal of the conditioned medium (containing released IFN-gamma). To demonstrate the immunosuppressive effects of IDO on the proliferation of PBMC, IDO-expressing FPCG treated with polymer-conjugated IFN-gamma were co-cultured with PBMC for a period of 5 days. The results showed a significant reduction in proliferation of PBMC co-cultured with IFN-gamma-treated IDO-expressing fibroblasts, compared to those co-cultured with non-IDO-expressing fibroblasts (P < 0.001). The addition of an IDO inhibitor (1-methyl-D-tryptophan) reversed the suppressive effects of IDO on PBMC proliferation. In conclusion, IDO expression in FPCG suppresses the proliferation of immune cells in vitro. The use of a temperature-sensitive polymer further prolongs the effect of IFN-gamma on the expression of IDO. Therefore, modulating IDO levels in situ might be an alternative for prolonging the survival of skin allografts.

Antineoplastic Agents↗

PubMed1993

Chiral separation using molecularly imprinted heteroaromatic polymers.

Novel molecularly imprinted polymer systems utilizing 4-vinylpyridine and 1-vinylimidazole as functional monomers have been developed for enantioselective recognition of carboxylic and N-protected amino acids. Non-covalent interactions between the functional monomers and the template molecules were the source of the subsequent recognition sites in the resultant polymers. The capacity of the polymers for molecular recognition was investigated by using them as stationary phases in the HPLC mode. Polymers prepared with 4-vinylpyridine were found to be more efficient in racemic resolution than those prepared with 1-vinylimidazole. When applying a racemic mixture of the template molecule, the polymers showed highest affinity for the enantiomer used as template. Imprints of a racemic template molecule, as expected, did not exhibit enantioselectivity. The optimal molar ratio of 4-vinylpyridine to the template Cbz-L-Asp-OH in the polymerization mixture was determined to be 12:1. In addition to enantioselectivity, the investigated polymers demonstrated 'ligand selectivity', e.g., a Cbz-L-Asp-OH-imprinted polymer was able to separate Cbz-D,L-Asp-OH, but was unable to separate Cbz-D,L-Glu-OH.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Ion-exchange macroporous hydrophilic gel monolith with grafted polymer brushes.

The grafting of functional polymers to the pore surface of macroporous monolithic polyacrylamide cryogels was found to be an efficient and convenient method for the preparation of macroporous polyacrylamide gels, so-called cryogels (pAAm cryogels), with both controlled extent of functional group incorporated and with tailored surface chemistries. Anion-exchange polymer chains of poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) and poly([2-(methacryloyloxy)ethyl]-trimethylammonium chloride) (pMETA), and cation-exchange polymer chains of polyacrylate have been grafted onto pAAm cryogels using potassium diperiodatocuprate as initiator. It was possible to achieve the ion-exchange capacity up to 0.2-0.5 mmol/ml. The graft polymerization did not alter the macroporous structure of the pAAm cryogel, however the flow rate of solutes through the cryogel matrix decreased with increase in the density of polymer grafted. The sorption of low-molecular-weight (metal ion, dye) and high-molecular-weight (protein) substances on the grafted monolithic pAAm column has been studied. The results indicate that a 'tentacle'-type binding of protein to grafted polymer depended on the architecture of the grafted polymer layer and took place after a certain degree of grafting has been reached. The binding of proteins by tentacle-like polymer chains allowed for increasing the binding capacity for proteins on the grafted pAAm cryogels up to 6-12 mg/ml.

Acrylic Resins↗

PubMed2005

Development and characterisation of a molecularly imprinted polymer prepared by precipitation polymerisation for the determination of phenylurea herbicides.

New materials based on molecularly imprinted polymers (MIPs) have been developed for use as sorbents in solid phase extraction to preconcentrate some urea herbicides. In the preconcentration step, different molecularly imprinted polymers were tested using methacrylic acid (MAA) and 2-(trifluoromethyl)acrylic acid (TFMAA) as functional monomers, and linuron and isoproturon as templates. The best results were obtained when the polymer was synthesised using MAA with isoproturon as template. Another parameter evaluated was the way in which the polymer was obtained. We observed that the imprinted polymers obtained by precipitation displayed a greater capacity to retain the phenylureas. Studies conducted using scanning electron microscopy (SEM) revealed that the bulk polymerisation method is far from ideal owing to the random shape and size distribution of the particles obtained, whereas when polymerisation was carried out in precipitation microspheres were obtained. In order to confirm the interaction between the functional monomer and the template, 1H NMR (CD2Cl2) analyses were conducted. The results obtained suggest that the hydrogen and/or nitrogen of the amino group of the template would be involved in the formation of hydrogen bonds with the functional monomer. The imprinted polymer obtained by precipitation polymerisation with MAA as functional monomer and isoproturon as template can be applied to preconcentrate phenylureas when the sample is dissolved in toluene. The proposed methodology was employed to evaluate polymer selectivity towards humic acids and towards other herbicides.

Chemical Precipitation↗

PubMed2006

Hydrolyzable p(DMAPEMA) polymers for gene delivery.

The efficiency of cationic polymers as transfectants is thought to be closely related to their DNA association/dissociation properties. An incomplete polymer-DNA dissociation could explain the relatively low gene expression obtained with p(DMAEMA) polymers. Our approach was to synthesize a p(DMAEMA) analogue, p(DMAPEMA), bearing an hydrolyzable cationic group incorporated into the pendant chain with a view to improving transfection. The complexation of DNA with both polymers was studied by agarose gel electrophoresis, size and zeta potential measurements, as well as the dissociation of the polyplexes, after treatment by an anionic polymer, sodium hydroxide or heat. The transfection efficiencies of the polyplexes were evaluated with 293T and BHK21 cells in comparison with Exgen 500. P(DMAPEMA) polymers were able to complex DNA and to release it in a free intact form after an alkaline treatment or storage at 37 degrees C. Poly(aspartic acid) was unable to dissociate p(DMAPEMA) based polyplexes, in contrast to p(DMAEMA) ones. No transfection was obtained with p(DMAPEMA) with both cell lines. A slow hydrolysis under physiological conditions resulting in the absence of DNA unpacking or endosomal entrapment could explain these results. Better transfection results were obtained with polyplexes which were able to be dissociated by electrostatic interactions rather than ones which required the hydrolysis mechanism to release free DNA into cells. Scheme of hydrolyzable p(DMAPEMA) polymer.

Animals↗

PubMed2005

Vine-twining polymerization: a new preparation method for well-defined supramolecules composed of amylose and synthetic polymers.

In this article we describe a new method of polymerization called "vine-twining polymerization" for preparation of well-defined supramolecules, which are amylose-polymer inclusion complexes. The method was achieved by enzymatic polymerization of alpha-D-glucose-1-phosphate catalyzed by phosphorylase in the presence of various synthetic polymers such as polyethers, polyesters, poly(ester-ether), and amphiphilic block copolymer. Powder X-ray diffraction (XRD) and 1H-NMR measurements determined the structures of the products to be inclusion complexes. The XRD patterns were completely different from those of amylose and guest polymers. The 1H-NMR spectra of the products indicated that the structures were composed of amylose and guest polymers. The formation process of the inclusion complexes during the enzymatic polymerization was also evaluated. In addition, we revealed that the bulkiness of the end groups and the hydrophobicity of the guest polymers strongly affected the formation of the inclusion complexes. By means of this method of polymerization, a graft polymer having inclusion complexes as side chains was prepared. Furthermore, as an evolution of the "vine-twining polymerization," we attempted a system of parallel polymerization to form an inclusion complex of amylose with a strongly hydrophobic guest polymer.

Amylose↗

PubMed1994

Sugar binding polymers showing high anomeric and epimeric discrimination obtained by noncovalent molecular imprinting.

Noncovalent molecular imprinting of sugar compounds in ethylene glycol dimethacrylate-methacrylic acid copolymers yielded materials containing highly selective sugar binding sites. Investigation of a range of polymers demonstrated that the resulting polymer imprints have a high degree of both anomeric and epimeric selectivity favoring the original print molecule. In HPLC assays, a polymer imprinted using p-nitrophenyl-alpha-D-galactoside could separate the alpha and beta anomers of the same compound with near baseline resolution. A polymer imprinted using p-nitrophenyl-beta-D-galactoside showed similar results but with the beta anomers retained longer as expected. Anomeric discrimination of closely related sugars was also possible, with the degree of separation depending on the structural resemblance to the print molecule. Similarly, a polymer imprinted with p-nitrophenyl-alpha-L-fucoside could separate alpha/beta mixtures of p-nitrophenyl-L-fucoside with baseline resolution. Using radioligand displacement assays a polymer imprinted using octyl-alpha-D-glucoside was shown to bind methyl-alpha-D-glucoside with a 40-fold higher affinity than that for the beta-anomer. The epimeric selectivity was even more impressive: methyl-alpha-D-mannoside and methyl-alpha-D-galactoside had 130- and 240-fold lower affinity, respectively, than methyl-alpha-D-glucoside. The results are discussed in relation to possible uses of such polymers in separation and analysis.

Carbohydrates↗

PubMed1998

Polymer chain statistics and conformational analysis of DNA molecules with bends or sections of different flexibility.

The worm-like chain model has often been employed to describe the average conformation of long, intrinsically straight polymer molecules, including DNA. The present study extends the applicability of the worm-like chain model to polymers containing bends or sections of different flexibility. Several cases have been explicitly considered: (i) polymers with a single bend; (ii) polymers with multiple coplanar bends; (iii) polymers with two non-coplanar bends; and (iv) polymers comprised of sections with different persistence lengths. Expressions describing the average conformation of such polymers in terms of the mean-square end-to-end distance have been derived for each case. For cases (i) and (iv), expressions for the projection of the end-to-end vector onto the initial orientation of the chain are presented. The expressions derived here have been used to investigate DNA molecules with sequence-induced bending (A-tracts). Mean-square end-to-end distance values determined from a large number of A-tract containing DNA molecules visualized by scanning force microscopy resulted in an average bend angle of 13.5 degrees per A-tract. A similar study was performed to characterize the flexibility of double-strandedDNA molecules containing a single-stranded region. Analysis of their mean-square end-to-end distance yielded a persistence length of 1.3 nm for single-stranded DNA.

DNA↗

PubMed1994

Purification of rabbit C-reactive protein by affinity precipitation with thermosensitive polymer.

A method of purifying rabbit C-reactive protein (CRP) based on affinity coprecipitation with a thermosensitive polymer is developed. This polymer, which was obtained by conjugation of p-aminophenylphosphorylcholine (APPC) and poly-N-isopropylacrylamide derivative with reactivity to primary amino groups, exhibited a thermally reversible phase separation profile with a critical value at 32 degrees C and high affinity for CRP in the presence of Ca2+. When rabbit acute-phase serum was incubated with APPC-conjugated polymer in the presence of Ca2+ at 4 degrees C, only CRP was bound to this affinity polymer and coprecipitated by raising the temperature of the incubation mixture above 32 degrees C. After addition of cold EDTA solution to the precipitate followed by centrifugation at 38 degrees C, CRP was recovered from the polymer in more than 80% yield with no contaminants. The binding of CRP to APPC-conjugated polymer was dependent on concentrations of both CRP and the polymer.

Acrylamides↗

PubMed2003

Chiral resolution of derivatized amino acids using uniformly sized molecularly imprinted polymers in hydro-organic mobile phases.

Uniformly sized molecularly imprinted polymers (MIPs) for Boc-L-Trp were prepared using ethylene glycol dimethacrylate (EDMA) as the cross-linker, and methacylic acid (MAA) and/or 4-vinylpyridine (4-VPY) as the functional monomers or without use of a functional monomer. The MIPs prepared were evaluated using acetonitrile or a mixture of phosphate buffer and acetonitrile as the mobile phase. The Boc-L-Trp-imprinted EDMA polymers can recognize Boc-L-Trp by its molecular shape, and can thus afford the enantioseparation of Boc-Trp. Besides the molecular shape recognition, the hydrophobic interactions with the polymer backbones as well as the hydrogen-bonding interactions of Boc-L-Trp with carboxyl and pyridyl groups in the polymers should work for the retention and recognition of Boc-L-Trp on the imprinted MAA- co-EDMA and 4-VPY- co-EDMA polymers, respectively, in the hydro-organic mobile phase. The hydrogen-bonding interactions seem to become dominant when only acetonitrile is used as the mobile phase. The Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers gave the highest retentivity and enantioselectivity for Boc-Trp among the MIPs prepared. However, the simultaneous use of MAA and 4-VPY was not effective for the enantioseparation of Boc-Trp in a hydro-organic mobile phase. Furthermore, the baseline separation of Boc-Trp enantiomers was attained within 10 min on the Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers under the optimized HPLC conditions.

Acetonitriles↗

PubMed1998

Ecotoxicological hazard assessment of two polymers of distinctively different molecular weights.

Assessment of ecological risks during manufacturing, use, transport, and disposal are becoming increasingly important as planning tools during development of new products. The objective of this study was to establish the potential ecotoxicological hazard associated with two polycarboxylate polymers in water, sludge, sediment, and soil. The concentrations of both polymers were quantified using 14C-radiolabeled synthesis and liquid scintillation counting (LSC). The program included water column acute and chronic exposures with Ceriodaphnia dubia, Pimephales promelas, and Selenastrum capricornutum, sediment exposures with Chironomus riparius, and soil exposures with Eisenia foetida. Sludge treated with either polymer, from a semicontinuous activated sludge unit, was used to evaluate the effect on growth of five plants. The hazard assessment program for both polymers indicated a very low order of toxicity as defined by the U.S. EPA and OECD. Very small fractions of each polymer may not be removed by waste treatment and could accumulate in sediments, but should not pose a significant risk because of their low toxicity to benthic organisms. Terrestrial testing demonstrated that soil needs to be saturated with these chemicals to produce adverse effects. Bioaccumulation potential for both polymers was extremely low. Use of these polymers does not appear to pose a significant risk to the environment, based on their low inherent toxicity.

Animals↗