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Results for “Polystyrenes”

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At least 217 records · Page 12Linked to original sources

PubMed1982

Partial splenic embolization using polyvinyl alcohol foam, dextran, polystyrene, or silicone. An experimental study in dogs.

Partial splenic arterial embolization (50% reduction in flow) was evaluated in dogs using polyvinyl alcohol foam or microspheres (20-500 mu) made of dextran, polystyrene, or silicone. Dextran and polystyrene were found to be superior for several reasons: they were easier to use, did not shatter when agitated, and produced permanent, homogeneous, peripheral occlusion with only one administration. Partial embolization with dextran or polystyrene increased platelet levels within 1 week and markedly reduced splenic size with minimal if any collateral filling within 6 weeks. Microscopically, no acute infarction or necrosis was seen at 6 weeks; there was some fibrosis, but the remaining parenchyma appeared normal.

Animals↗

PubMedDate not supplied

Vacuum-ultraviolet photochemically initiated modification of polystyrene surfaces: chemical changes.

Fourier-Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet- (VUV-) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2-excimer radiation source (lambda(exc): 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1-2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography-mass spectrometry (GC-MS) revealed the presence of a large number of products. The application of pulsed Xe2-excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.

Journal Article↗

PubMed2004

Synthesis and crystallization of hybrid spherical colloids composed of polystyrene cores and silica shells.

The Stöber method has been adopted to prepare hybrid core-shell particles by coating the surfaces of monodisperse polystyrene beads with uniform silica shells. Polystyrene beads with diameters in the range of 0.1-1.0 microm have been successfully demonstrated for use with this process, and the thickness of the silica coating could be controlled in the range of 50-150 nm by adjusting the concentration of tetraethoxysilane, the deposition time, or both. The morphology and surface smoothness of the deposited silica were found to strongly depend on a number of parameters such as the surface functional groups on the polymer beads, the pH value of the medium, and the deposition time. Hollow spheres made of silica could be obtained by selectively removing the polymer cores via calcination in air at an elevated temperature or by wet etching with toluene. These core-shell colloids were also explored as building blocks to fabricate long-range ordered lattices (or colloidal crystals) that exhibited stop bands different from those assembled from spherical colloids purely made of either polystyrene or silica.

Journal Article↗

PubMed1998

Concanavalin A-immobilized polystyrene nanospheres capture HIV-1 virions and gp120: potential approach towards prevention of viral transmission.

To establish an effective tool for the prevention of HIV-1 transmission, lectin-immobilized polystyrene nanospheres were synthesized and examined for their HIV-1 capture activity. When concanavalin A (Con A) was immobilized on the surface of polystyrene nanospheres (400 nm in diameter) with poly(methacrylic acid) branches and incubated with HIV-1 suspension at room temperature for 60 min, the nanospheres (Con A-NSs) achieved a >3.3 log and a 2.2 log reduction of viral infectivity in HIV-1 (IIIB strain) suspension at a concentration of 2 and 0.5 mg/ml, respectively. Meanwhile, Con A-free nanospheres, which were not immobilized with Con A, achieved only a 0.29 log reduction at 0.5 mg/ ml. Con A-NSs (2 mg/ml) could also reduce the gp120 level of III(B) and HE strains to <7.1% and 5.5% of each control, respectively. The combination of Con A-NS treatment followed by filtration with a microporous membrane efficiently removed virion-free gp120 as well as infectious viral particles from HIV-1 suspension. Electron microscopic examination demonstrated that HIV-1 virions were trapped on the surface of Con A-NSs. Thus, Con A-NSs can capture HIV-1 virions and gp120 with high affinity, and may have potential as an effective tool for the prevention of HIV-1 transmission.

Concanavalin A↗

PubMed1997

Randomly phosphorylated polystyrene derivatives interact with RNA polymerase II transcription factors: part I.

Insoluble functional synthetic random copolymers are able to develop at their surfaces specific interactions with biologic components. Crosslinked phosphorylated polystyrene derivatives were previously shown to mimic DNA antigen because they interacted with anti-DNA antibodies found in the sera of systemic lupus erythematosus patients. These biospecific surfaces were postulated to be able to bind other DNA-binding proteins such as RNA polymerase II transcription factors. Indeed, these proteins play a major role in gene regulation in mammalian cells. This hypothesis was checked by adsorption and elution of HeLa cell nuclear extracts on a 72% phosphorylated resin. The composition of the eluted fractions were analyzed by electrophoresis, and the biologic activity of the transcription factors was tested using an in vitro transcription assay. The results showed that USF, TATA-binding protein (TBP), and TFIIB were specifically adsorbed on the polymer and that all eluted factors kept their biologic activity. Therefore, randomly phosphorylated polystyrene derivatives may be useful for the fractionation of RNA polymerase II transcription factors.

Adsorption↗

PubMed1998

Fibronectin adsorption, conformation, and orientation on polystyrene substrates studied by radiolabeling, XPS, and ToF SIMS.

Protein adsorption is widely studied by a variety of techniques, but there still is little known about protein orientation and conformation after adsorption. This probably is due to the large number of parameters involved, such as the characteristics of the surface and the structure of the protein. In this study, the adsorption of fibronectin was investigated with three different techniques: radiolabeling, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF SIMS) on polystyrene and oxidized polystyrene. The first two techniques have been widely used to study protein adsorption, allowing us to determine the amount of protein adsorbed on each surface. The ToF SIMS, however, is a technique just emerging for the study of protein adsorption. This study confirms its utility since ToF SIMS is found to be sensitive to the protein orientation and/or conformation at the surface. Indeed, the ToF SIMS peaks characteristic of the protein show differences in their reduced intensity between the two substrates. These differences, which are not detected by XPS, are attributed to different orientations and/or conformations of the protein.

Adsorption↗

PubMed1996

Alteration of the aPA ELISA by UV exposure of polystyrene microtiter plates.

Interlaboratory inconsistencies in antiphospholipid antibody (aPA) solid phase assays have prompted controversy in clinical laboratory testing for aPA. We found that the aPA ELISA can be influenced by the type of microtiter plate utilized and by the conditions in which the plates are stored. By exposing 96-well, flat-bottom polystyrene microtiter plates to short wave UV light (254 nm), the aPA ELISA signal decreased in a UV dose-dependent manner. No effect was seen with long wave UV light (366 nm). These results were independent of the antibody isotype under study or the phospholipid (PL) antigen used: anionic phosphatidylserine (PS) and cardiolipin (CL), or zwitterionic phosphatidylethanolamine (PE). Purified human beta 2-glycoprotein I (beta 2 GPI), a known cofactor for anionic PL, and rabbit anti-beta 2 GPI antisera were used to demonstrate that beta 2 GPI bound equally to UV treated and untreated microtiter plates. In contrast, recognition of beta 2 GPI on an anionic PL surface was decreased on UV treated plates, suggesting that UV exposure alters the lipid binding properties of the microliter plate. To determine whether UV exposure inhibited PL binding directly or caused a change in the way the PL was bound, the amount of PL bound to UV treated and untreated plates was measured by using fluorescent labeled PS and a fluorimeter. PS binding was decreased by 53% in UV treated wells as compared to untreated wells. These data show that short wave UV exposure reduces PL binding to polystyrene microtiter plates, thereby reducing the amount of beta 2 GPI bound to PL coated ELISA plates. Thus by using UV exposed microtiter plates, decreased or false-negative a PA ELISA results may be obtained for aPA positive plasmas.

Animals↗

PubMed2001

Heparin-carrying polystyrene (HCPS)-bound collagen substratum to immobilize heparin-binding growth factors and to enhance cellular growth.

Heparin-carrying polystyrene (HCPS), consisting of low molecular weight heparin chains linked to a synthetic polystyrene core, is able to attach to polymeric surfaces. In this study, HCPS has efficiently bound to collagen-coated micro-plates and collagen membranes thereby retaining the binding of heparin-binding growth factors, such as vascular endothelial growth factor (VEGF)(165) or fibroblast growth factor (FGF)-2. Both human skin fibroblast cells and human umbilical vein endothelial cells have shown a good adherence to both collagen- and HCPS-bound collagen substrata. The growth rate of the fibroblast cells on the HCPS-bound collagen substratum in the presence of low concentrations of FGF-2 is higher than on a collagen surface. The fibroblast cells grow at a significantly higher rate on the HCPS-bound collagen substratum retained with FGF-2. Similarly, the growth rate of the endothelial cells on the HCPS-bound collagen substrata in the presence of low concentrations of either FGF-2 or VEGF(165) is higher than on collagen. The endothelial cells also grow at a significantly higher rate on the HCPS-bound collagen substratum retained with either FGF-2 or VEGF(165). These results indicate that HCPS-bound collagen substrata with various bioactive heparin-binding molecules may provide novel biomaterials controlling cellular activities such as growth and differentiation.

Biocompatible Materials↗

PubMed2001

Spatially resolved single bead analysis: homogeneity, diffusion, and adsorption in cross-linked polystyrene.

Spatially resolved single bead analysis in the micrometer range was employed as a tool for evaluating homogeneity, diffusion, and adsorption in solid-phase supported reactions. Fluorescence microscopy (confocal and non-confocal) as well as IR microscopy were used to detect both the distribution of products and the formation of product gradients in representative reactions. For the first time, the optical slices of whole beads obtained by confocal fluorescence microscopy were compared with the fluorescence images of microtome-sliced beads. The experiments revealed that only physical slices of polystyrene beads deliver realistic representations of the distribution of fluorophores, and confirmed-in contrast to a recent report-the homogeneity of functional site distribution in polystyrene beads. Moreover, the pattern of product formation obtained from an acylation reaction as well as from an alkylation reaction were employed as probes to study the impact of bead size, diffusion, and adsorption on the reaction progress. A simulation of the diffusion process was conducted and compared with the experimental results. Diffusional control was found neither in the case of the alkylation nor in the case of the acylation reaction under investigation. As a consequence, the reaction progress was not a function of the bead sizes as proposed in the literature. Interestingly, in the case of rhodamine acylation with substoichiometric amounts an adsorption-controlled reaction was found. This result highlights the significance of adsorptive effects in solid-phase supported chemistry.

Adsorption↗

PubMed2000

Analysis of plasma protein adsorption onto polystyrene particles by two-dimensional electrophoresis: comparison of sample application and isoelectric focusing techniques.

Two-dimensional electrophoresis (2-DE) was previously established for analysis of plasma protein adsorption patterns on particulate carriers for intravenous drug targeting. This study addresses a possible effect of polymeric particles on protein separation in the first dimension, e.g., hindrance of protein entry into the gel or interaction of particles with the gel matrix. Polystyrene beads of mean diameter 100, 200 and 1000 nm were used as model carriers. Two different separation techniques were performed in the first dimension of 2-DE to study possible interactions of the beads with the different gel matrices, i.e., carrier ampholytes (CA) and immobilized pH gradients (IPGs). Comparison of gels obtained from samples including the particles from samples separated from the polystyrene beads showed no noteworthy differences. Therefore, a negative effect of the particles can be excluded, and particle separation from the sample is not necessary. Another goal of this study was the transfer of analytical protocols for isoelectric focusing from CA to IPGs with regard to enhanced reproducibility, faster sample processing, and easier handling. Transfer from CA to IPGs was carried out successfully and showed improved resolution of basic proteins. In contrast to that, lower amounts of a few high molecular mass proteins were detected, especially when sample application cups were employed. A qualitative change in the obtained protein pattern was not observed. Increased entry of high molecular weight proteins was achieved by in-sample rehydration instead of using sample cups.

Acrylic Resins↗

PubMed2002

Ethylene oxide and propylene oxide random copolymer/sodium chloride aqueous two-phase systems: wetting and adsorption on dodecyl-agarose and polystyrene.

Liquid/liquid partition chromatography is a mild yet powerful separation method for a variety of biological materials. This work demonstrates that it should be feasible to immobilize an ethylene oxide-propylene oxide (EO/PO) random copolymer solution and to use a solution of NaCl equilibrated against the polymer solution as the mobile-phase (poly (EO-PO) [P(EO-PO)] and NaCl form two aqueous phases known as aqueous two-phase systems). Three random copolymers with different molecular weights and EO/PO ratios were used. Dodecyl-agarose and polystyrene were tested as possible supports. The wetting energies of the aqueous two-phase systems on these two kinds of surfaces were calculated as well as contact angles for each phase on the same surfaces. Finally, the thickness of P(EO-PO) adsorption layers on polystyrene lattices were measured by dynamic light scattering. Contact angle measurements indicate that indeed some EO/PO copolymers preferentially wet hydrophobic substrates, forming thin films.

Adsorption↗

PubMed1992

Reduction of fibrinogen adsorption on PEG-coated polystyrene surfaces.

Reduction of protein adsorption by coating surfaces with polyethylene glycol (PEG) is well documented. The present work has four goals related to these previous studies: first, to develop chemistry providing densely packed, covalently bound PEG on polystyrene (PS); second, to determine the ability of these modified surfaces to reject fibrinogen; third, to compare the protein-rejecting ability of branched and linear PEGs; and fourth, to examine the utility of an ELISA-type procedure for measuring protein adsorption. It was found that PEG-epoxide could be readily coupled to amine groups of poly(ethylene imine) (PEI), which had been preadsorbed onto an oxidized PS surface. The PEG groups on branched PEGs appear to act as an excluded volume to repel proteins, similar to arguments previously raised for linear PEGs. The results of protein adsorption studies showed that fibrinogen adsorption is significantly reduced by coating polystyrene with either linear or branched PEGs of 1500 to 20,000 in molecular weight. The ELISA technique was found to be equivalent in sensitivity to radiolabeled fibrinogen for estimating adsorption levels. It is expected that PEG-coated PS will have much utility in a variety of biomedical applications.

Adsorption↗

PubMed1993

Conformational changes of fibronectin induced by polystyrene derivatives with a heparin-like function.

It was previously reported that polystyrene substituted with the sulfonate group, PSSO3, which has anticoagulant heparin-like properties, and then coated with fibronectin supports the growth of human umbilical vein endothelial cells. On the other hand, polystyrene substituted with the amino acid sulfamide group, PSSO2-Asp, which has a higher anticoagulant activity, and then coated with fibronectin no longer supported the growth of endothelial cells. We report here that, while the affinity of fibronectin to either polymer is of the same order of magnitude, fibronectin is adsorbed onto the PSSO2-Asp polymer in a different conformation compared to the PSSO3 polymer. This was shown by a higher binding of polyclonal antifibronectin antibodies to fibronectin-coated PSSO2-Asp polymer, and by a decreased susceptibility of the coated fibronectin to proteolysis by thermolysin. This study provides evidence that a solid phase substrate with a strong heparin-like function may influence the conformation and biological properties of fibronectin.

Absorption↗

PubMed1993

Behavior of primary bone cells on characterized polystyrene surfaces.

Primary bone cells, isolated from the periosteally stripped calvariae of neonate rats, were cultured on 60Co gamma-irradiation-sterilized bacteriologic-grade polystyrene that had been either surface treated with concentrated sulfuric acid or received further gamma-irradiation treatments facilitated cell colonization of the polystyrene compared to those surfaces not treated in the laboratory. x-Ray photoelectron spectroscopy (XPS) showed that the two treatments introduced different chemical groups onto the polymer surface and that cell adhesion was related to gamma-irradiation in a dose-dependent manner. These results show that simple biologic assays, such as cell colonization, are not able to distinguish between differences in surface chemistry demonstrated by such a routinely employed surface analysis technique. Thus, there is a need to develop more sensitive biologic assays that provide functional information of a precision that can be correlated with subtle changes in substratum surface chemistry. Further, we argue that because cells isolated by tissue digestion using proteolytic enzymes respond more readily to changes in the surface chemistry of the substratum they colonize, compared to explanted cells; biologic assays designed for biomaterials testing must take into account changes effected in cell adhesion behavior by isolation procedures.

Animals↗

PubMed2004

Pegylated polystyrene particles as a model system for artificial cells.

Pegylated polystyrene particles (PS-PEG) were prepared as a model system for artificial cells, by modification of carboxyl polystyrene particles (PS-COOH) with homo- and hetero-bifunctional polyethylene glycols (PEG, MW 1500, 3400, and 5000) containing an amino end group for immobilization and an amino, hydroxyl, or methoxy end group that is exposed at the surface after immobilization. Protein adsorption from human plasma dilutions (85 v %) onto PS-PEG with a PEG surface concentration higher than 40 pmol/cm2 was reduced up to 90-95% compared with protein adsorption onto PS-COOH with a final protein surface concentration of approximately 30 ng/cm2. Two-dimensional gel electrophoresis analyses showed that 30% of the total amount of adsorbed proteins onto PS-PEG are dysopsonins (i.e., nonadhesive proteins like albumin and apolipoproteins). For PS-COOH, <15% of the amount of adsorbed proteins are dysopsonins. In addition, the generation of terminal complement compound (TCC) by PS-PEG particles with a PEG surface concentration lower than approximately 55 pmol/cm2 is not significant. The low protein adsorption, the relatively high percentage of adsorbed dysopsonins, and the low level of complement activation may prevent the uptake of PS-PEG by the mononuclear phagocytic system (MPS) in vivo. Moreover, PS-PEG (PEG surface concentration > approximately 35 pmol/cm2) shows minimal interaction with cultured human umbilical vein endothelial cells (HUVEC), which mimics the endothelial lining of the blood vessel wall.

Adsorption↗

PubMed1977

Sulphonated polystyrene as an optimal substratum for the adhesion and spreading of mesenchymal cells in monovalent and divalent saline solutions.

Cell adhesion and spreading were studied on sulphonated polystyrene dishes in serum-free saline (Mn, Na, Cl, buffer) i.e., without an intervening protein layer. Spreading as a function of surface charge density, SCD, peaked around 2-10 negative charges per square nanometer, corresponding to a monomolecular layer of sulphonate ions. At optimal SCD, macrophages, BHK-C13 and whole mouse embryo secondary cells all showed considerable spreading, even in monovalent saline-more so than on a conventional tissue-culture surface. But outside this narrow range of SCD, or on protein-coated surfaces, the divalent cation was indispensable. The biphasic effect of sulphonation on cell adhesion is consistent with the theory that a substratum need not be biochemically specific, provided it is physiochemically polar, rigid and dense. According to this theory, polystyrene of sub-optimal SCD would not be sufficiently polar, while supra-optimal sulphonation would produce a hydrogel surface, lacking in local rigidity and density, due to osmotic swelling. The principle of polymer exclusion, by a surface hydrogel layer, is also consistent with observations on the inhibitory effects of adsorbed proteins-viz., albumin, collagen, serum and cellular exudate, respectively-contrasted with the ready attachment of cells to a bare, optimally charged substratum, in this minimal in vitro system.

Animals↗

PubMed2002

An efficient gel-phase synthesis of peptides on a high capacity flexible crosslinked polystyrene support: comparison with Merrifield resin.

A highly solvating copolymer was prepared in high yield by introducing a flexible crosslinker, 1,4-butanedioldimethacrylate, into the polystyrene matrix by a free radical aqueous suspension polymerization. A 2 mol% crosslinked resin showed rigidity and mechanical characteristics comparable to those of divinylbenzene-crosslinked polystyrene (Merrifield resin, DVB-PS) support. Swelling and solvation characteristics of the new resin, BDDMA-PS, were much higher than DVB-PS support in all solvents used for solid phase peptide synthesis. The diacrylate crosslinks in the resin network were found to be highly stable even after 48 h treatment with neat TFA, 6 N HCl and 6 N KOH at 110 degrees C. To demonstrate the usefulness of the new resin in high capacity peptide synthesis, a typical difficult peptide, acyl carrier protein (ACP) fragment (65-74), was synthesized on commercially available 1 mol% crosslinked DVB-PS and 2 mol% crosslinked BDDMA-PS resins under identical conditions. A protocol using NMP/DMSO mediated coupling was employed for chain assembly. The yield and purity of the product from BDDMA-PS resin was higher than when the DVB-PS resin was used. The mechanistic reason behind the synthetic efficiency of the new resin was found to be its ability to induce random coil conformation to the growing peptide chains.

Chromatography, High Pressure Liquid↗

PubMed1994

Polystyrene reverse-phase ion-pair chromatography of chimeric ribozymes.

The use of a reverse-phase polystyrene resin for ion-pair HPLC purification of large amounts of synthetic chimeric DNA-RNA oligomers that is faster and more reliable than previously used techniques has been developed. The preparation of synthetic oligomers containing RNA requires the use of tetrabutylammonium fluoride in the final step, the cleavage of the tert-butyl-dimethyl silyl protecting group from the ribonucleotides. Cleavage is accompanied by the serendipitous formation of ion pairs between tetrabutylammonium cations and the oligomer phosphates. The formation of these ion pairs retards the elution of the oligomer during HPLC, which allows rapid removal of excess tetrabutylammonium fluoride and the concomitant purification of chimeric ribozymes. This technique is based on a correlation between the length of ion-paired oligomers and their retardation during HPLC. The advantages of reverse-phase ion-pair HPLC on polystyrene resin for the fast purification of oligoribonucleotides are discussed and illustrated through the examples of synthesized chimeric ribozymes.

Base Sequence↗