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PubMed2001

Adsorption of Poly(ethylene oxide)-Poly(lactide) Copolymers. Effects of Composition and Degradation.

The effect of chemical degradation of two diblock copolymers of poly(ethylene oxide) (E) and poly(lactide) (L), E(39)L(5) and E(39)L(20), on their adsorption at silica and methylated silica was investigated with in situ ellipsometry. Steric stablization of polystyrene dispersions was investigated in relation to degradation. Hydrolysis of the poly(lactide) block of the copolymers was followed at different temperatures and pH by using HPLC to measure the occurrence of lactic acid in solution. The block copolymers were quite stable in pH-unadjusted solution at low temperature, whereas degradation was facilitated by increasing temperature or lowering of the pH. Lower degradation rates of E(39)L(20) where observed at low temperature in comparison with those of E(39)L(5), whereas the degradation rates of the copolymers were quantitatively similar at high temperature. The adsorption of the copolymers at methylated silica substrates decreased with increasing degree of degradation due to the reduction in the ability of hydrophobic block to anchor the copolymer layer at the surface. At silica the adsorption initially increased with increasing degradation, particularly for E(39)L(20) due to deposition of aggregates onto the surface. After extensive degradation the adsorption of the copolymers at both silica and methylated silica resembled that of the corresponding poly(ethylene oxide) homopolymer. Overall, it was found that the eventual reduction in adsorption occurred at a lower degree of degradation for E(39)L(5) than for E(39)L(20). Mean-field calculations showed a reduced anchoring for the block copolymers with decreasing poly(lactide) block length at hydrophobic surfaces. In accordance with this finding, it was observed that polystyrene dispersions were stabilized by E(39)L(20) or E(39)L(5) in a way that depended on both the lactide block length and the degree of degradation. Upon degradation of the hydrophobic block, stabilization of the polystyrene dispersions was maintained initially, but eventually degradation resulted in destabilization. The average residual copolymer concentration required for stabilization of the polystyrene dispersions was much higher than the corresponding concentration of intact copolymer required for stabilization. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

Hydrophobic Core/Hydrophilic Shell Amphiphilic Particles.

Amphiphilic colloidal particles with hydrophobic cores and hydrophilic shells were prepared via a two-step method. First, polystyrene cores were obtained through the concentrated emulsion polymerization. A mixture of styrene, ethyl benzene, divinyl benzene, azobisisobutyronitrile, and cumene hydroperoxide (CHPO) was partially polymerized at 80 degrees C for 40 min and subsequently used as the dispersed phase of a concentrated emulsion in water. The concentrated emulsion was subjected to complete polymerization at 60 degrees C for 12 h; colloidal particles of crosslinked polystyrene were thus obtained. In the second step, the polystyrene particles were dispersed in water, after which acrylamide, N,N'-methylenebisacrylamide, and ferrous sulfate (FS) were added. The system was heated (typically at 30 degrees C) to conduct the polymerization of the hydrophilic monomers. The CHPO present on the surface of the polystyrene particles and the FS present in the aqueous phase (both together constitute a redox initiator) ensured that the initiation occurred mostly on the surface of the particles and that the hydrophilic polymer obtained formed a shell encapsulating the particles. Under proper conditions, a porous outer shell could be generated, making the hydrophobic core accessible to the outside medium. Copyright 2001 Academic Press.

Journal Article↗
PubMed1989

The immunochemistry of sandwich ELISAs--III. The stoichiometry and efficacy of the protein-avidin-biotin capture (PABC) system.

The protein-avidin-biotin capture (PABC) system was developed to decrease the adsorption-induced loss of antigen capture capacity (AgCC) of capture antibodies (CAb) used in sandwich ELISAs. This system involves immobilization of biotinylated CAbs through linkage by streptavidin (SA) to biotinylated carrier proteins adsorbed on polystyrene. Studies reported here describe the stoichiometry of the system and the influence of biotinylation of different carrier proteins and CAbs on the reaction stoichiometry and the AgCC of CAbs. Because of the widespread use of sandwich ELISAs to measure the concn of multivalent protein antigens, the AgCCs of monoclonal and polyclonal CAbs to pig IgG in the PABC system were compared with the AgCCs of these Abs immobilized on the plastic by direct adsorption. Optimal assay conditions for the carrier were obtained when 1 microgram/ml of the biotinylated protein was added to the polystyrene solid phase. An increasing degree of biotin substitution in three carrier proteins was paralleled by an increasing AgCC until a constant maximum was reached. Under conditions of maximal AgCC, 120 ng of the carrier rabbit gamma globulin (RGG; i.e. RGG25biot) was bound to polystyrene, which in turn yielded the maximum amount (i.e. 100 ng) of bound streptavidin (SA; Bdngmax) when 20 micrograms/ml of SA was added. Under conditions giving the Bdngmax for SA, CAb12biot yielded a higher Bdngmax than did CAb25biot or CAb2biot. When the AgCC of equal amounts of differentially biotinylated CAbs were compared, the following order of AgCC was observed: CAb12biot greater than CAb12biot greater than CAb25biot. Hence, while the maximal amount of CAb is immobilized on SA when CAb12biot is used, optimal AgCC is achieved with CAb2biot. The carrier:SA:CAb2biot ratio was 1:2:1 while that for carrier:SA:CAb12biot was 1:2:2. The same ratio was obtained using IgG2biot from four different species. Monoclonal antibodies to swine IgG showed a 5-6-fold increase in Bd%max when immobilized as CAbs using the PABC system versus when adsorbed on polystyrene. Plots of these data suggest that the differences result from a loss of functional affinity. On the contrary, no significant differences in Bd%max and hence functional affinity were observed when a polyclonal antibody to pig IgG was compared using the two assay configurations. Furthermore, when the globulin fraction of the anti-pig polyclonal was adsorbed on plastic, it behaved nearly as well as its affinity-purified counterpart immobilized by the PABC system. The PABC system appears to offer significant advantages for sandwich ELISAs utilizing monoclonal antibodies as the CAb, and may offer some advantages in other s

Adsorption↗
PubMed2006

Peptide-PEG amphiphiles as cytophobic coatings for mammalian and bacterial cells.

Amphiphilic macromolecules containing a polystyrene-adherent peptide domain and a cell-repellent poly(ethylene glycol) domain were designed, synthesized, and evaluated as a cytophobic surface coating. Such cytophobic, or cell-repellent, coatings are of interest for varied medical and biotechnological applications. The composition of the polystyrene binding peptide domain was identified using an M13 phage display library. ELISA and atomic force spectroscopy were used to evaluate the binding affinity of the amphiphile peptide domain to polystyrene. When coated onto polystyrene, the amphiphile reduced cell adhesion of two distinct mammalian cell lines and pathogenic Staphylococcus aureus strains.

Amino Acid Sequence↗
PubMed2004

Comparison of styrene-divinylbenzene-based monoliths and Vydac nano-liquid chromatography columns for protein analysis.

This report details the fabrication of polystyrene-based nano-LC monolithic columns for the separation of protein molecules. The report focuses on the practical advantages of monolithic columns when compared to conventional packed columns. Capillary columns were made to 100 and 50 microm i.d. and used to analyse a mixture of proteins, these separations were then compared with a conventional protein phase under the same conditions. A second functionalised monolithic polystyrene-based column was also manufactured and compared for the analysis of proteins, under the same analytical conditions, to the standard non-functionalised bare polystyrene monolith. Nano-LC polystyrene monolithic columns were found to be advantageous to conventional phases for the analysis of protein molecules, with a one-step fabrication process, faster analysis times, lower limits of detection hence higher sensitivity.

Chromatography, Liquid↗
PubMed2005

Contactless conductivity detection of synthetic polymers in non-aqueous size-exclusion electrokinetic chromatography.

A capacitively coupled contactless conductivity detection (CCD) system has been applied for the detection of neutral synthetic polymers in capillary size-exclusion electrokinetic chromatography (SEEC). Polystyrene standards, that were used as a model compounds, were separated on a capillary column packed with porous 10 microm silica particles with an electrokinetically driven mobile phase, and detected by CCD and UV detection simultaneously. Mass-calibration curves for polystyrene were constructed. Satisfactory results were obtained for the linearity, the run-to-run repeatability (<0.2% for the relative retention and <4% for the peak area) and the robustness of the detector. One of the major issues in this preliminary study was to investigate the origin of the peaks observed for the polystyrene standards. The effect of the molar mass of the polystyrenes on the sensitivity was small. Therefore, the signals obtained could not be explained as the result of an increased viscosity and a decreased solution conductivity of the solute zone. An alternative hypothesis is suggested, and recommendations for further research are given.

Calibration↗
PubMed2004

Fabrication of sub-micrometer-sized jingle bell-shaped hollow spheres from multilayered core-shell particles.

Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell.

Journal Article↗
PubMed2005

Macroporous ZrO2 ceramics prepared from colloidally stable nanoparticles building blocks and organic templates.

ZrO2 macroporous materials with well-ordered structures were prepared using nano-ZrO2 particles as the building materials and polystyrene spheres as the organic templates. A well-dispersed nano-ZrO2 suspension with a narrow particle size distribution was prepared by deagglomeration of as-received nano-ZrO2 powders via ultrasonication, and then centrifugation was performed to remove agglomerated bigger particles. Negatively charged polystyrene spheres were uniformly coated with positively charged nano-ZrO2 particles by means of electrostatic attraction at pH 4. Green samples were prepared by slip casting from colloidally stable suspension of nano-ZrO2 coated polystyrene spheres. ZrO2 macroporous materials with well-ordered microstructure derived from the nano-ZrO2 coated polystyrene spheres.

Journal Article↗
PubMed2006

Biofilm formation by field isolates and reference strains of Haemophilus parasuis.

The ability to form biofilms for a total of 80 field isolates and 15 reference strains of Haemophilus parasuis, the etiological agent of Glasser's disease, was tested by glass tube and polystyrene microtiter plate assays. A total 43% of field isolates, including strains representing 13 serovars (except serovars 3 and 8) and non-typable strains, exhibited the ability to form biofilms at different levels via polystyrene microtiter plate assays. Among the reference strains representing 15 serovars, only serovars 2, 9, 12, 13 and 15 could not form biofilms on the polystyrene surface. A total of 85% of the strains forming biofilms at air-liquid interfaces in glass tubes also formed biofilms on polystyrene surfaces. Generally, non-virulent serovars showed a higher degree of biofilm formation than virulent serovars. The biofilm formation phenotype of most strains was maintained when cultures were passaged on agar and in broth. H. parasuis from the nasal cavities of pigs experimentally infected with biofilm-positive bacteria maintained the biofilm formation phenotype, whereas bacteria recovered from the lung and brain lost the ability to form biofilms. The biofilm-negative strains did not recover the ability to form biofilms via experimental infection. Our data indicate that most serovars of H. parasuis could form biofilms in vitro, and the biofilm formation phenotype is associated with the recovery site of the strains and is maintained when bacteria are passaged in vitro and in the upper respiratory tract.

Animals↗
PubMed1998

Further characterization of Staphylococcus epidermidis transposon mutants deficient in primary attachment or intercellular adhesion.

Biofilm formation is suggested to be the result of primary attachment of Staphylococcus epidermidis cells to a polymer surface followed by accumulation in multilayered cell clusters. Here we describe the further characterization of transposon (Tn917) mutants of Staphylococcus epidermidis O-47 having been biofilm-negative in a polystyrene microtiter plate adhesion assay. Among 5000 Tn917 insertion strains, we isolated four biofilm-negative mutants, each carrying one copy of Tn917. The mutants could be divided into two phenotypic classes: class A (mut1 and mut1a) and class B (mut2 and mut2a). Mutants of phenotype class A lacked four cell surface proteins and were affected in the primary attachment to polystyrene, but remained able to form multilayered cell clusters and to produce PIA. Mutants of phenotype class B were able to attach to polystyrene, but did not form multilayered cell clusters nor produce PIA. The cell surface protein pattern relative to the wild type was unchanged in class B mutants. On Congo red agar, the wild type and class A mutants formed black colonies (positive reaction on Congo red agar) while class B mutant colonies were red (negative reaction). The initial binding of cells to polystyrene and the ability to form multilayered cell clusters were found to be phenotypically and genetically distinct traits.

Adhesins, Bacterial↗
PubMedDate not supplied

A facile solid-phase synthesis of substituted 2(5H)-furanones from polymer-supported alpha-selenocarboxylic acids.

The synthesis of polystyrene-supported alpha-selenoacetic acid, alpha-selenopropionic acid, and alpha-selenophenylacetic acid is described. The reaction of the dilithio derivatives of polymer-supported alpha-selenocarboxylic acids with racemic epoxides or optically active styrene oxide afforded polystyrene-supported gamma-substituted alpha-selenobutyrolactones. The alpha-alkylation reaction of gamma-substituted polystyrene-supported alpha-selenobutyrolactones provided another route for the synthesis of polystyrene-supported alpha,gamma-disubstituted alpha-selenobutyrolactones. Subsequent oxidation-elimination with an excess of 30% hydrogen peroxide at room temperature afforded substituted (3- and 5-mono-; 3,4- and 3,5-di) 2(5H)-furanones in high yields and good purities.

Journal Article↗
PubMed2005

Determining the conformation of an adsorbed Br-PEG-peptide by long period X-ray standing wave fluorescence.

Long-period X-ray standing wave fluorescence (XSW) and X-ray reflectivity techniques are employed to probe the conformation of a Br-poly(ethylene glycol) (PEG)-peptide adsorbate at the hydrated interface of a polystyrene substrate. The Br atom on this Br-PEG-peptide construct serves as a marker atom allowing determination by XSW of its position and distribution with respect to the adsorption surface with angstrom resolution. Adsorption occurs on native or ion-beam-modified polystyrene films that are spin-coated onto a Si substrate and display either nonpolar or polar surfaces, respectively. A compact, oriented monolayer of Br-PEG-peptide can be formed with the peptide end adsorbed onto the polar surface and the PEG end terminating with the Br tag extending into the aqueous phase. The 108-141 A distance of the Br atom from the polystyrene surface in this oriented monolayer is similar to the estimated approximately 150 A length of the extended Br-PEG-peptide. This Br-polystyrene distance depends on adsorption time and surface properties prior to adsorption. Incomplete multilayers form on the polar surface after sufficient adsorption time elapses. By contrast, adsorption onto the nonpolar surface is submonolayer, patchy, and highly disordered with an isotropic Br distribution. Overall, this combination of X-ray surface scattering techniques with a novel sample preparation strategy has several advantages as a real space probe of adsorbed or covalently bound biomolecules at the liquid-solid interface.

Adsorption↗
PubMed2006

Latex and hollow particles of reactive polypyrrole: preparation, properties, and decoration by gold nanospheres.

Polypyrrole-coated polystyrene latex particles bearing reactive N-amino functional groups (PS-PPyNH2) were prepared by the in-situ copolymerization of pyrrole (Py) and the active amino-functionalized pyrrole (PyNH2) in the presence of 1.33 microm-diameter polystyrene (PS) latex particles. These particles were prepared by dispersion polymerization of styrene using poly(N-vinylpyrrolidone), PNVP, as a steric stabilizer. The functionalized polypyrrole-coated PS particles (PS-PPyNH2) were characterized in terms of their particle size and surface morphology using transmission electron microscopy (TEM). Infrared and X-ray photoelectron spectroscopy (XPS) detected pyrrole-NH2 repeat units at the surface of the latex particles, indicating that this monomer had indeed copolymerized with pyrrole. The core-shell structure of the PS-PPyNH2 particles was confirmed by etching the polystyrene core in THF, leading to the formation of hollow conducting polymer capsules. The PS-PPyNH2 particles were then decorated with citrate-stabilized gold nanoparticles via electrostatic interactions. Furthermore, etching of the polystyrene core resulted in the formation of gold-decorated PPyNH2 hollow capsules.

Journal Article↗
PubMed1999

Spleen capture of nanoparticles: influence of animal species and surface characteristics.

PURPOSE: To investigate the influence of animal species and nanoparticle surface characteristics on the intrasplenic distribution of polystyrene nanoparticles. METHODS: Two types of fluorescent polystyrene nanoparticles (Estapor and Fluoresbrite), plain or coated, were used in mice and rats. First, a fluorimetric method was developed for nanoparticle tissue quantification. Then, intrasplenic distribution of plain or coated nanoparticles was studied using histological examination and image analysis. Finally, the role of direct interactions between nanoparticles and spleen capturing cells was assessed by in vitro binding assays, using incubation of thick spleen slices with polystyrene nanoparticles. RESULTS: The two types of polystyrene nanoparticles showed different levels of trapping: Fluoresbrite nanoparticles were more efficiently trapped by the spleen than Estapor nanoparticles, both in mice and rats. In mice, most of the injected nanoparticles were localized in the marginal zone of the spleen, involving a special population of capturing cells, while in rats, the predominant capture occured in the red pulp. In mice, coated nanoparticles were localized both in the marginal zone and in the red pulp, whereas the coating did not seem to change the intrasplenic distribution of the nanoparticles in rats. CONCLUSIONS: These complementary approaches showed different uptake pathways of nanoparticles, according to their surface characteristics and the rodent species used.

Animals↗
PubMed1994

Surface modification of poly(lactide-co-glycolide) nanospheres by biodegradable poly(lactide)-poly(ethylene glycol) copolymers.

The modification of surface properties of biodegradable poly(lactide-co- glycolide) (PLGA) and model polystyrene nanospheres by poly(lactide)-poly(ethylene glycol) (PLA:PEG) copolymers has been assessed using a range of in vitro characterization methods followed by in vivo studies of the nanospheres biodistribution after intravenous injection into rats. Coating polymers with PLA:PEG ratio of 2:5 and 3:4 (PEG chains of 5000 and 2000 Da. respectively) were studied. The results reveal the formation of a PLA:PEG coating layer on the particle surface resulting in an increase in the surface hydrophilicity and decrease in the surface charge of the nanospheres. The effects of addition of electrolyte and changes in pH on stability of the nanosphere dispersions confirm that uncoated particles are electrostatically stabilized, while in the presence of the copolymers, steric repulsions are responsible for the stability. The PLA:PEG coating also prevented albumin adsorption onto the colloid surface. The evidence that this effect was observed for the PLA:PEG 3:4 coated nanospheres may indicate that a poly(ethylene glycol) chain of 2000 Da can provide an effective repulsive barrier to albumin adsorption. The in vivo results reveal that coating of PLGA nanospheres with PLA:PEG copolymers can alter the biodistribution in comparison to uncoated PLGA nanospheres. Coating of the model polystyrene nanospheres with PLA:PEG copolymers resulted in an initial high circulation level, but after 3 hours the organ deposition data showed values similar to uncoated polystyrene spheres. The difference in the biological behaviour of coated PLGA and polystyrene nanospheres may suggest a different stability of the adsorbed layers on these two systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

A novel carrier for Phanerochaete chrysosporium immobilization.

Phanerochaete chrysosporium BKMF-1767 cells were immobilized on different carriers. The optimum carrier according to adsorbed P. chrysosporium cells number (86.38%) was determined to be polystyrene foam, a novel carrier. The conditions for the immobilization of cells on polystyrene foam were optimized and determined as 50 rpm, 37 degrees C, and 2h. The results show that the adsorption of P. chrysosporium on polystyrene foam follows the Langmuir adsorption isotherm. High manganese peroxidase activity (421 U/L) and dry mass (4.7 g/L) were recovered from the batch mode polystyrene foam solid state fermentation system.

Bioreactors↗
PubMed1992

Conversion of ionization measurements to radiation absorbed dose in non-water density material.

The radiation absorbed dose to non-water equivalent materials of interest in radiotherapy is the dose to lung and the dose to bone. The measurement and calculation of dose to the lung has been of great interest and much effort has gone into the development of accurate lung dose calculation methods. The radiation absorbed dose to the bone is usually not calculated and most absorbed dose calculations have been done without correcting for the presence of bone. For the lower megavoltage photon beams this may be appropriate, however, as the energy of the photon beam increases, the region of electronic disequilibrium becomes larger and pair production which depends on the atomic number of the material becomes significant. Therefore the bone will produce greater perturbations of the dose distribution. The dose to lung-equivalent material is uniquely obtained from ionization measurements. However, in bone-equivalent materials two different calculations of absorbed dose are possible: the absorbed dose to soft tissue plastic (polystyrene) within bone-equivalent material and the dose to the bone-equivalent material itself. Both can be calculated from ionization measurements in phantoms. These two calculations result in significantly different doses in a heterogeneous phantom composed of polystyrene and aluminium (a bone substitute). The dose to a thin slab of polystyrene in aluminium is much higher than the dose to the aluminium itself at the same depth in the aluminium. Monte Carlo calculations confirm that the calculation of dose to polystyrene in aluminium can be accurately carried out using existing dosimetry protocols. However, the conversion of ionization measurements to absorbed dose to high atomic number materials cannot be accurately carried out with existing protocols and appropriate conversion factors need to be determined.

Bone and Bones↗
PubMed1990

Detection of one milliattomole of ferritin by novel and ultrasensitive enzyme immunoassay.

A novel and ultrasensitive enzyme immunoassay (immune complex transfer two-site enzyme immunoassay) for ferritin is described. Ferritin was reacted simultaneously with affinity-purified dinitrophenyl biotinyl anti-ferritin IgG and affinity-purified anti-ferritin Fab'-beta-D-galactosidase conjugate. The complex formed of the three components was trapped onto affinity-purified (anti-dinitrophenyl group) IgG-coated polystyrene balls. After eliminating excess conjugate by washing, the complex was eluted from the polystyrene balls with an excess of epsilon N-dinitrophenyl-L-lysine and transferred to streptavidin-coated polystyrene balls. The beta-D-galactosidase activity bound to streptavidin-coated polystyrene balls was assayed by fluorometry. Nonspecifically bound beta-D-galactosidase activity was remarkably lowered but there was much less decrease in specifically bound beta-D-galactosidase activity. As a result, the detection limit of ferritin was lowered to 1 milliattomole (1 x 10(-21) mol, 600 molecules as calculated from Avogadro's number). This technique will be useful for measuring, for example, antigens in single cells.

Antigen-Antibody Complex↗