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At least 667 records · Page 37Linked to original sources
PubMed2005

Morphology of rhenium complex-containing polystyrene-block-poly(4-vinylpyridine) and its use as self-assembly templates for nanoparticles.

Polystyrene-block-poly(4-vinylpyridine) was functionalized with a chlorotricarbonyl rhenium(I) diimine complex. Compared to the metal-free copolymer, the copolymer-metal complex exhibited different morphologies, which are highly sensitive to the solvent used for spin-coating and the surface properties of the substrates. Well-defined cylindrical or spherical domains were observed. Due to its ionic nature, the poly(4-vinylpyridine)--rhenium complex block could also serve as a template for subsequent deposition of cadmium sulfide nanoparticles by electrostatic attraction. The pattern of the deposited nanoparticles was found to be the replica of the block copolymer underneath, and their presence on the film surface was confirmed by X-ray photoelectron spectroscopy.

Macromolecular Substances↗
PubMed2005

Protein micropatterning using surfaces modified by self-assembled polystyrene microspheres.

A technique for micropatterning of proteins on a nonplanar surface to improve the coverage and functionality of biomolecules is demonstrated. A nonplanar microstructure is created by the self-assembly of polystyrene microspheres into an array of microwells on a silicon wafer to allow the integration of a nonplanar spot on a planar chip. After the microspheres were deposited into the microwells, they were conjugated with proteins. The curve surfaces of the microspheres present more surface area for attaching biomolecules which will increase the density of biomolecules and, hence, the sensitivity for detection. Moreover, proteins immobilized on a curved surface can retain their native structures and function better than on a planar surface because of a smaller area of interaction between the protein and the substrate. Patterning of biomolecules was tested with two model fluorescent proteins. The results show that precise patterning of biomolecules on a nonplanar spot can be achieved with this technique.

Microscopy, Electron, Scanning↗
PubMed2005

Covalently anchored lipid structures on amine-enriched polystyrene.

The study of the adhesion of lipid vesicles on surfaces is of increasing interest in the field of medical implants and tissue engineering (protein-resistant surfaces), drug delivery, biosensors, and biochips. In this work, lipid coverage was developed from PEG-coated vesicles (with sizes from 100 to 300 nm) by covalently binding poly(ethylene glycol)-alpha-disteroylphosphatidylethanolamine-omega-benzotriazole carbonate (DSPE-PEG-BTC) molecules onto the surface amine groups by carbamate chemistry. Lipid surface density and the surface structure of multilamellar (MLVs) and extruded unilamellar (LUVs) vesicles deposited on three types of polystyrene (PS) well-plates were probed by fluorescence and atomic force microscopy (AFM) imaging. A significant difference in the vesicle surface coverage of PS substrates was observed with a substantial increase in lipid multilayers on the amine-enriched PS surface using both unilamellar and multilamellar vesicles.

Amines↗
PubMed2005

Electrostatically tuned interactions in silica microsphere-polystyrene nanoparticle mixtures.

We explore the generality of nanoparticle haloing as a novel colloidal stabilization mechanism in binary mixtures of silica microspheres and polystyrene nanoparticles. By selectively tuning their electrostatic interactions, both the initial microsphere stability and the role of nanoparticle additions are varied. Adsorption isotherm and zeta potential measurements indicate that highly charged nanoparticles exhibit a weak (haloing) association with negligibly charged microspheres, whereas they either strongly adsorb onto oppositely charged or are repelled by like-charged microsphere surfaces, respectively. Bulk sedimentation and confocal scanning fluorescence microscopy reveal that important differences in system stability emerge depending on whether the added nanoparticles serve as haloing, bridging, or depletant species.

Microspheres↗
PubMed2005

Size-selective protein adsorption to polystyrene surfaces by self-assembled grafted poly(ethylene glycols) with varied chain lengths.

We report about the surface modification of polystyrene (PSt) with photoreactive alpha-4-azidobenzoyl-omega-methoxy poly(ethylene glycol)s (ABMPEG) of three different molecular weights (MWs of approximately 2, approximately 5, and approximately 10 kg/mol) and with two poly(ethylene glycol)/poly(propylene glycol) triblock copolymers (PEG-PPG-PEG) of about identical PEG/PPG ratio (80/20, w/w) and MW(PEG) of approximately 3 and approximately 6 kg/mol, all via adsorption from aqueous solutions. For ABMPEGs, an additional UV irradiation was used for photografting to the PSt. Contact angle (CA) and atomic force microscopy data revealed pronounced differences of the hydrophilicity/hydrophobicity and topography of the surfaces as a function of PEG type and concentration used for the modification. In all cases, an incomplete coverage of the PSt was observed even after modification at the highest solution concentrations (10 g/L). However, clear differences were seen between PEG-PPG-PEGs and ABMPEGs; only for the latter was a nanoscale-ordered interphase structure with an influence of MW(PEG) on the PEG density observed; after modification at the same solution concentrations, the density was significantly higher for lower MW(PEG). The adsorption of three proteins, myoglobin (Mgb), bovine serum albumin (BSA), and fibrinogen to the various surfaces was analyzed by surface plasmon resonance. Pronounced differences between the two PEG types with respect to the reduction of protein adsorption were found. At high, but still incomplete, surface coverage and similar CA, the shielding of ABMPEG layers toward the adsorption of Mgb and BSA was much more efficient; e.g., the adsorbed Mgb mass relative to that of unmodified PSt was reduced to 10% for ABMPEG 2 kg/mol while for both PEG-PPG-PEGs the Mgb mass was still around 100%. In addition, for the ABMPEG layers an effect of MW(PEG) on adsorbed protein mass-decrease with decreasing MW-could be confirmed; and the highest Mgb/BSA selectivities were also observed. A "two-dimensional molecular sieving", based on PEG molecules having a nanoscale order at the hydrophobic substrate polymer surface has been proposed, and the main prerequisites were the use of PEG conjugates which are suitable for an "end-on" grafting (e.g., ABMPEGs), the use of suitable (not too high) concentrations for the surface modification via adsorption/self-assembly, optionally the photografting on the substrate (possible only for ABMPEG), and presumably, a washing step to remove the excess of unbound PEGs. The results of this study also strongly support the hypothesis that the biocompatibility of hydrophobic materials can be very much improved by PEG modifications at surface coverages that are incomplete but have an ordered layer structure controlled by the size and steric interactions of surface-bound PEGs.

Adsorption↗
PubMed2006

Synthesis of quantum dot-tagged submicrometer polystyrene particles by miniemulsion polymerization.

Submicrometer fluorescent polystyrene (PS) particles have been synthesized via miniemulsion polymerization using CdSe/ZnS core-shell quantum dots (QDs). The influence of QD concentration, QD coating (either trioctylphosphine oxide (TOPO)-coated or vinyl-functionalized), and surfactant concentration on the polymerization kinetics and the photoluminescence properties of the prepared particles has been analyzed. Polymerization kinetics were not altered by the presence of QDs, whatever their surface coating. Latexes exhibited particle sizes ranging from 100 to 350 nm, depending on surfactant concentration, and a narrow particle size distribution was obtained in all cases. The fluorescence signal of the particles increased with the number of incorporated TOPO-coated QDs. The slight red shift of the emission maximum was correlated with phase separation between PS and QDs, which occurred during the polymerization, locating the QDs in the vicinity of the particle/water interface. QD-tagged particles displayed higher fluorescence intensity with TOPO-coated QDs compared to those with the vinyl moiety. The obtained fluorescent particles open up new opportunities for a variety of applications in biotechnology.

Cadmium Compounds↗
PubMed2005

Ring-shaped morphology in solution-cast polystyrene-poly(methyl methacrylate) block copolymer thin films.

We report observation of ring-shaped morphology formed in thin films of a cylinder-forming polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer cast from 1,1,2,2-tetrachloroethane (Tetra-CE) solution via relatively fast solvent evaporation rates, in which Tetra-CE is a good solvent for both blocks but preferential affinity for the minority PMMA block. We studied the microstructure of a set of solution-cast block copolymer films dried with different solvent evaporation rates, R. The control with different R leads to keeping microstructures in different solution concentrations (phi) and bringing mechanical strain fields with different strength in the film, for which faster evaporation rates result in microstructures of lower solution concentrations and mechanical strain fields of higher strength. As R decreases from rapid evaporation (approximately 0.1 mL/h), the film microstructure evolved from an intermediate ringlike morphology sequentially to ring-shaped morphologies including loose and tight rings and then inverted phase of PS spheres in a PMMA matrix and finally reached the equilibrium phase, namely, cylinders of PMMA in a PS matrix. In view of the influence of the film constraints, the microstructure of a film with a terraced free surface profile has been examined. The results indicate that the ring-shaped morphology can form as long as the film thickness is larger than a critical value of about one microdomain spacing. In the case where the film thickness is larger than that value, the nature of solvent and the kinetics of solvent evaporation are shown to be mainly responsible for the ring-shaped morphology formation.

Nanostructures↗
PubMed2005

Model systems for flavoenzyme activity: site-isolated redox behavior in flavin-functionalized random polystyrene copolymers.

[reaction: see text] A model system has been developed to study the redox behaviors of flavin derivatives appended onto random polystyrene copolymers through "click" chemistry strategies. The results demonstrate that flavin units attached onto polymers exhibit site-isolated redox behaviors, yielding new materials with electrochemically tunable associations (K(a)(ox) = 450 M(-)(1), K(a)(red) = 18,200 M(-)(1)) to complementary diamidopyridine (DAP) functionality.

Electrochemistry↗
PubMed1998

Binding of carbohydrates to solid supports Part 3: Reaction of sugar hydrazones with polystyrene substituted with aromatic aldehydes.

The hydrazones of glucose and N-acetylglucosamine, as models for the residues at the reducing termini of glycans, were covalently and reversibly bound in good yield to hydroxybenzaldehydo ligands attached to a polymer support. The binding, by a sugar azine linkage, occurred within two hours at room temperature at neutral pH, and efficient recoveries of sugars from the beads were achieved by displacement with aqueous hydrazine hydrate, ethanolic benzaldehyde, or aqueous acetone. Enzyme modification of glycans was demonstrated by separation of the products of hydrolysis of lactose hydrazone with beta-galactosidase, using hydroxybenzaldehyde-derivatized polystyrene beads. Addition of a spacer arm to aminopolystyrene beads, for binding of reducing sugars as Amadori compounds to the aromatic amine function, was also investigated.

Acetylglucosamine↗
PubMed2001

Synthesis of esculentin-1 antibacterial peptide fragments on 1,4-butanediol dimethacrylate cross-linked polystyrene support.

Peptide segments corresponding to antibacterial esculentin-1 (1-15), (3344), (9-27), and their modified forms were synthesized on 1,4-butanediol dimethacrylate cross-linked polystyrene (PS-BDODMA) support. Hydroxymethyl and aminomethyl 2% PS-BDODMA supports were used for the synthesis. The HMPB linker was appended to the aminomethyl resin using HBTU in presence of HOBt and the first amino acid was incorporated using MSNT. The conventional Fmoc synthetic protocol was used for the synthesis of peptides. The peptides were cleaved from the support using TFA. The peptides were purified by HPLC, and characterized by amino acid analysis and MALDI TOF MS. The secondary structures of the peptides were revealed by CD measurements. The synthesis of these peptides illustrates the utility of the new support for the synthesis of long-chain bioactive peptides. The synthetic peptides were tested for antimicrobial activity against Escherichia coli Mos blue, E. coli 2, Bacillus brevis, B. megaterium, Pseudomonas HTL, and Vibrio mimicus. The antibacterial activity of the peptides was explained on the basis of the helicity and charged nature of the sequences.

Amino Acid Sequence↗
PubMed1990

Development of a preformulation lipophilicity screen utilizing a C-18-derivatized polystyrene-divinylbenzene high-performance liquid chromatographic (HPLC) column.

Alkane/water partition coefficients have been predicted from the retention times of solutes using a C-18-derivatized polystyrene-divinylbenzene HPLC column (Act-I). Several classes of compounds, with molecular weights from 78 to 379 and partition coefficients ranging over several orders of magnitude, were included in the present study. A high correlation coefficient (0.953) was obtained from log-log plots of alkane/water partition coefficients versus capacity factor. A poor correlation was observed for octanol/water partition coefficient, presumably due to the hydrogen-bonding capability of octanol. The alkane/water correlation suggests that the system is devoid of significant specific solute-stationary phase interactions which are known to impart anomalous retention behavior to traditional reverse phase columns. Deviations of calculated alkane/water partition coefficients (and Hansch II alkane coefficients) from observed values could not be explained in terms of solute (or substituent) polarizability, dipole moment, sigma para, or pKHB values, further suggesting that specific interactions between the stationary phase and the solute are not significant. A molecular weight dependence that was independent of lipophilicity was observed. Thermodynamic and extra-thermodynamic parameters of retention were obtained in order to investigate retention mechanisms for the Act-I column. The molecular weight dependence does not appear to be due to size exclusion or entropic expulsion of the solute from the stationary phase. Hansch II substituent coefficients calculated from retention times were found to be similar for benzene and steroid derivatives. Thus, the Act-I column may be utilized as a rapid lipophilicity screen for drug candidates of similar molecular weight.

Alkanes↗
PubMed1994

Polystyrene-poly (ethylene glycol) (PS-PEG2000) particles as model systems for site specific drug delivery. 2. The effect of PEG surface density on the in vitro cell interaction and in vivo biodistribution.

The effect of differing densities of poly (ethylene glycol-2000) (PEG2000) at the particle surface of polystyrene-poly (ethylene glycol-2000) (PS-PEG2000) particles was assessed in terms of hydrophobic interaction chromatography (HIC) and the in vitro and in vivo behaviour of the particles. The particles, with different surface densities of PEG, were prepared by varying the copolymerizing reaction of styrene with a PEG macromonomer. There is a clear relationship between the surface density of PEG as determined by X-ray photoelectron spectroscopy and surface hydrophobicity as assessed by hydrophobic interaction chromatography (HIC). Similarly, the interaction of the particles with non-parenchymal liver cells in in vitro studies was shown to decrease as the surface density of PEG increases. The in vivo study investigating the biodistribution of the PS-PEG particles after intravenous injection into rats reveals that a relationship exists between the surface density of PEG and the extent to which the particles remain in the circulation, avoiding recognition by the reticuloendothelial system. Particles with the higher surface densities show increased circulatory times which compared well with data for particles prepared with the surface adsorbed PEO-PPO block copolymer, Poloxamine 908.

Animals↗
PubMed2003

Tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene: a new resin support for solid-phase peptide synthesis.

A highly flexible, mechanically and chemically stable copolymer, tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene (PS-TRPGGDA), was synthesized by the suspension polymerization and employed as a solid support for peptide synthesis. The beaded polymer support containing secondary hydroxyl functional groups in the cross-linker was used as the growth site for peptide synthesis. The procedure is unique and cost-effective in that it avoids the initial functionalization steps required for most of the styrene-based polymer supports. The resin was characterized by 13C-CP-MAS NMR spectroscopy and the morphologic features of the resin were investigated using scanning electron microscopy. Swelling studies conducted on the new support revealed that the PS-TRPGGDA resin undergoes more effective swelling and solvation than PS-DVB resin in all solvents used in peptide synthesis. The efficiency of the new support was demonstrated by synthesizing a 'difficult' sequence Ala-Arg-(Ala)6-Lys and comparing it with commercially available Merrifield and Sheppard resins. The synthetic efficiency was further demonstrated by the synthesis of a 24-residue NR 2A peptide substrate of calcium/calmodulin-binding peptide. The high yield and purity of the peptide synthesized on the novel support indicates the positive role of the flexible and hydrophilic cross-linking agent in the solid support.

Acrylates↗
PubMed1979

The polystyrene vacuum wheelchair cushion.

A polystyrene bead vacuum wheelchair cushion has been tried with several patients with abnormal postural reflex activity. Excess spasticity can be reduced by this means and sitting comfort enhanced.

Humans↗
PubMed2000

Simultaneous determination of dihydroxybenzenes, aminophenols and phenylenediamines in hair dyes by high-performance liquid chromatography on hypercross-linked polystyrene.

The retention of polar organic molecules such as dihydroxybenzenes, aminophenols and phenylenediamines on a 250 x 4.6 mm id column packed with 5 microns hypercross-linked polystyrene Chromalite 5HGN (Purolite) was studied. The influence of separation parameters such as concentration of acetonitrile, buffer (citrate, phosphate) concentration, ionic strength and pH of the eluent on their retention was investigated. Under optimum conditions [acetonitrile-0.3 mol l-1 ammonium phosphate, pH 5.15 (30:70 v/v)], eight substances generally used as dye intermediates in hair colouring compositions could be separated within 20 min. An HPLC method with spectrophotometric detection is proposed for the simultaneous determination of pyrocatechol, resorcinol, hydroquinone, o-, m- and p-aminophenols and p-phenylenediamine in commercial haircolour products. The detection limits of these compounds are in the range 0.05-0.16 microgram ml-1. The suitability of the method is demonstrated by the analysis of three different permanent hair dyes.

Aminophenols↗
PubMed2004

Electroactive layer-by-layer films of heme protein-coated polystyrene latex beads with poly(styrene sulfonate).

In this work, a novel two-step construction strategy for protein layer-by-layer assembly films was proposed. In the first step, positively charged hemoglobin (Hb) or myoglobin (Mb) at pH 5.0 was adsorbed on the negatively charged surface of 500 nm diameter-sized polystyrene (PS) latex beads, forming core-shell structured PS-protein particles. In the next step, the PS-protein particles were further assembled layer by layer with oppositely charged poly(styrene sulfonate)(PSS) on various solid surfaces under suitable conditions. Cyclic voltammetry (CV), quartz crystal microbalance (QCM), and UV-vis spectroscopy were used to monitor the growth of {(PS-protein)/PSS}(n) films. The stable {(PS-protein)/PSS}(n) films modified on pyrolytic graphite (PG) electrodes demonstrated good electroactivity in protein-free buffer, which was originated from protein heme Fe(III)/Fe(II) redox couples, and the electroactivity extended to six (PS-protein)/PSS bilayers. UV-vis spectroscopy showed that Hb and Mb in the films retained their near-native structure in the medium pH range. {(PS-protein)/PSS}(n) films catalyzed electrochemical reduction of oxygen, hydrogen peroxide, trichloroacetic acid (TCA) and nitrite with a significant lowering of overpotential, and displayed better catalytic activity than corresponding cast PS-protein films.

Animals↗