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PubMed2004

Plasma-treated polystyrene surfaces: model surfaces for studying cell-biomaterial interactions.

Biocompatibility of biomaterials relates, amongst others, to the absence of adverse cellular reactions and modulation of cell adhesion and subsequent responses. With respect to tissue-engineering applications, most materials need to evoke cell adhesion and spreading, while potentially displaying differential cell function. Adhesion has frequently been studied in a controlled fashion, using adhesion-supporting and -inhibiting substrata. The aim of this study is to create a panel of related materials with gradually changing surface characteristics in order to sustain similar individual cell adhesion and spreading, yet different cell population behaviour. A series of polystyrene materials was created with increasing oxygen surface incorporation and, concurrently, decreasing water-contact angles. Individual cells adhered and spread on all surfaces whilst showing well-developed focal adhesions and stress fibres. Cell populations demonstrated a decreased growth on surfaces with lower wettability. The biochemical activity of cell populations was not influenced by the surface treatment, but cell proliferation on surfaces increased with increasing oxygen incorporation. Furthermore, surface coverage with assembled fibronectin matrix was higher on the substrata with higher wettability. Finally, the expression of the adhesion-related proteins cadherin-5, focal adhesion kinase and RhoA was increased on surfaces with higher wettability. Further explorations of the cell biological basis of the observed differential behaviour will give more detailed answers on the rules governing cell-material interactions.

Biocompatible Materials↗
PubMed2004

Gap junction communication between cells aggregated on a cellulose-coated polystyrene: influence of connexin 43 phosphorylation.

The appropriate functioning of tissues and organ systems depends on intercellular communication such as gap junctions formed by connexin (Cx) protein channels between adjacent cells. We have previously shown that Swiss 3T3 cells aggregated on hydrophilic cellulose substratum Cuprophan (CU) establish short linear gap junctions composed of Cx 43 in cell surface plaques. This phenomenon seems to depend on the high intracellular cyclic AMP (cAMP) concentration triggered by attachment of the cells to CU. We have now used a cellulose-coated polystyrene inducing the same cell behaviour to analyse the gap junction communication between aggregated cells. The transfer of the dye Lucifer Yellow (LY) between cells showed that cells aggregated on cellulose substratum rapidly (within 90 min) establish functional gap junctions. Inhibitors of cAMP protein kinase (PKI) or protein kinase C (GF109203X) both inhibited the diffusion of LY between neighbouring cells. Western blot analysis showed that this change in permeability was correlated with a decrease in Cx 43 phosphorylation. Thus, cellulose substrata seem to induce cell-cell communication through Cx 43 phosphorylation modulated by PKA and PKC. To understand the mechanisms by which a substratum regulates gap junctional communication is critically important for the emerging fields of tissue engineering and biohybrid devices.

Animals↗
PubMed2004

Oriented astroglial cell growth on micropatterned polystyrene substrates.

In an effort to develop a permissive environment for neural stem cell differentiation, directional growth of astrocytes has been achieved on polymer substrates in vitro. Manipulating a combination of physical and chemical cues, astrocyte adhesion and alignment in vitro were examined. To provide physical guidance, micropatterned polymer substrates of polystyrene (PS) were fabricated. Laminin was selectively adsorbed onto the grooves of the patterned surface. Rat type-1 astrocytes were seeded onto the micropatterned PS substrates, and the effects of substrate topography and the adsorption of laminin to the PS substrates on the behavior and morphology of the astrocytes were explored. The astrocytes were found to align parallel to the micropatterned grooves at initial seeding densities of approximately 7500, 13,000, and 20,000 cells/cm(2) due to the effects of the physical and chemical guidance mechanisms. Adsorbing laminin in the microgrooves of the micropatterned PS substrates improved cell adhesion and spreading of cytoskeletal filaments significantly. At these initial seeding densities, over 85% astrocyte alignment in the direction of the grooves was achieved on the micropatterned PS substrates with laminin adsorbed in the grooves. This combination of guidance cues has the potential to provide a permissive substrate for in vivo regeneration within the central nervous system.

Animals↗
PubMed2005

Osteoblast alignment, elongation and migration on grooved polystyrene surfaces patterned by Langmuir-Blodgett lithography.

Topographically patterned surfaces are known to influence cellular behavior in a controllable manner. However, the relatively large surface areas (several cm2) required for many biomaterial applications are beyond the practical limits of traditional lithography. Langmuir-Blodgett lithography, a recently developed method, was used to fabricate regularly spaced grooves of different depths (50 and 150 nm) with a periodicity of 500 nm over several square centimeter on silicon surfaces. These topographies were transferred into polystyrene surfaces by means of nanoimprinting. Primary osteoblasts were cultured on the patterned polymer surfaces. They were observed to align, elongate and migrate parallel to the grooves. The combination of Langmuir-Blodgett lithography with nanoimprinting enables the fabrication of large, nanostructured surface areas on a wide spectrum of different biomaterials. Osteoblasts show a significant anisotropic behavior to these surfaces, which can enhance cell settlement on the surface or be used to direct tissue generation on the biomaterial interface.

Actinin↗
PubMed2005

An inverted microcontact printing method on topographically structured polystyrene chips for arrayed micro-3-D culturing of single cells.

With the goal to investigate the relation of shape and function of single cells or clusters of cells in a 3-dimensional (3-D) microenvironment, we present a novel platform technology to create arrays of microwells on polystyrene (PS) chips for hosting cells in a local microenvironment characterized by controlled shape and surface chemistry. The micro-3-D cell culturing combines 2-dimensional chemical patterning with topographical microstructuring presenting to the cells a local 3-D host structure. Microwells of controlled dimensions were produced by a two-step replication process, based on standard microfabrication of Si, replica molding into poly(dimethylsiloxane), and hot embossing of PS. This allowed the production of large numbers of microstructured surfaces with high reproducibility and fidelity of replication. Using inverted micro contact printing, the plateau surface between the microwells was successfully passivated to block adsorption of proteins and prevent cell attachment by transfer of a graft-copolymer, poly(l-lysine)-g-poly(ethylene glycol). The surface inside the microwells was subsequently modified by spontaneous adsorption of proteins or functionalized PLL-g-PEG/PEG-X (X=biotin or specific, cell-interactive peptide) to elicit specific responses inside the wells. Preliminary cell experiments demonstrated the functionality of such a device to host single epithelial cells (MDCK II) inside the functionalized microwells and thus to control their 3-D shape. This novel platform is useful for fundamental cell-biological studies and applications in the area of cell-based sensing.

Adsorption↗
PubMed2006

Monitoring cell adhesion on tantalum and oxidised polystyrene using a quartz crystal microbalance with dissipation.

The quartz crystal microbalance with dissipation (QCM-D) (Q-Sense AB, Sweden) has been established as a useful tool for evaluating interactions between various biological and non-biological systems, and there has been increasing interest in using the QCM-D technique for cell monitoring applications. This study investigated the potential of the QCM-D to characterise the initial adhesion and spreading of cells in contact with protein precoated biocompatible surfaces. The QCM-D technique is attractive for monitoring cell adhesion and spreading as it allows in situ real-time measurements. The adhesion of NIH3T3 (EGFP) fibroblasts to tantalum (Ta) and oxidised polystyrene (PS(ox)) surfaces precoated with serum proteins was examined using the QCM-D for a period of either 2 or 4 h. Time-lapse photography was performed at 30 min intervals to visually examine cell adhesion and spreading in order to relate cell morphology to the QCM-D response. Following adsorption of albumin, fibronectin or newborn calf serum onto the surfaces, QCM-D measurements showed that cells adhered and spread on the fibronectin and serum coated surfaces, while few cells adhered to the albumin coated surfaces. Cells adhered to albumin coated surfaces had a rounded morphology. The responses to fibronectin and serum precoated surfaces were quite different for each of the underlying substrates indicating that the process of cell adhesion and spreading elicits different responses depending on both the protein coating composition and the influence of the underlying substrate. The different response may be due to extracellular matrix remodelling as well as cytoskeletal changes. Frequency (f) and dissipation (D) changes associated with cell adhesion were less than would be expected from the Sauerbrey relation due to the viscoelastic properties of the cells.

Absorption↗
PubMed2005

Mild and efficient oxidation of alcohols with sodium periodate catalyzed by polystyrene-bound Mn(III)porphyrin.

Mild and efficient oxidation of primary and secondary alcohols with sodium periodate catalyzed by Mn(TPyP), [manganese(III)tetra(4-pyridyl)porphyrin], supported on chloromethylated polystyrene, [Mn(TPyP)-CMP], at room temperature were reported. This catalyst can be reused consecutively four times in the oxidation of 4-chlorobenzyl alcohol in 97% yield without significant loss of its activity.

Alcohols↗
PubMed2004

Quantitation of osteoblast-like cell mineralization on tissue culture polystyrene and Ti-6Al-4V alloy disks by Tc-99m-MDP labeling and imaging in vitro.

Technetium-99m-methylene-diphosphonate (Tc-99m-MDP) labeling was used to quantify mineralization of cultures of MC3T3 osteoblast-like cells in vitro. MC3T3 cells were cultured on tissue culture polystyrene (TCPS) in mineralizing and non-mineralizing media, and then labeled by Tc-99m-MDP. The gamma signal from labeled samples was imaged with a gamma camera and compared with the calcium content in the same samples determined by inductively coupled plasma. The high correlation (coefficient of determination, 0.88) between these two values validated the radiotracer uptake method as a quantitative analytical tool for certain mineralization studies in vitro. There was an association between mineralization and radionuclide uptake in the MC3T3 cultures on titanium alloy, but the attenuation of the gamma photons by the metal resulted in a less robust correlation. The results warrant implementation of this scintigraphic method for quantitative studies of osteoblast-mediated mineralization in vitro.

3T3 Cells↗
PubMed2004

Voltammetric studies of hemoglobin-coated polystyrene latex bead films on pyrolytic graphite electrodes.

A novel hemoglobin (Hb)-coated polystyrene (PS) latex bead film was deposited on pyrolytic graphite (PG) electrode surface. In the first step, positively charged Hb molecules in pH 5.0 buffers were adsorbed on the surface of negatively charged, 500 nm diameter PS latex beads bearing sulfate groups by electrostatic interaction. The aqueous dispersion of Hb-coated PS particles was then deposited on the surface of PG electrodes and, after evaporation of the solvent, Hb-PS films were formed. The Hb-PS film electrodes exhibited a pair of well-defined, quasi-reversible cyclic voltammetric (CV) peaks at about -0.36 V vs. SCE in pH 7.0 buffers, characteristic of Hb heme Fe(III)/Fe(II) redox couples. Positions of Soret absorption band of Hb-PS films suggest that Hb retains its near-native structure in the films in its dry form and in solution at medium pH. The Hb in PS films was also acted as a catalyst to catalyze electrochemical reduction of various substrates such as trichloroacetic acid (TCA), nitrite, oxygen and hydrogen peroxide.

Animals↗
PubMed2006

Alkaline hydrothermal treatment of brominated high impact polystyrene (HIPS-Br) for bromine and bromine-free plastic recovery.

A method to recover both Br and Br-free plastic from brominated flame retardant high impact polystyrene (HIPS-Br) was proposed. HIPS-Br containing 15% Br was treated in autoclave at 280 degrees C using water or KOH solution of various amounts and concentrations. Hydrothermal treatment (30 ml water) leads to 90% debromination of 1g HIPS-Br but plastic is strongly degraded and could not be recovered. Alkaline hydrothermal treatment (45 ml or 60 ml KOH 1M) showed similar debromination for up to 12 g HIPS-Br and plastic was recovered as pellets with molecular weight distribution close to that of the initial material. Debromination occurs at melt plastic/KOH solution interface when liquid/vapour equilibrium is attained inside autoclave (280 degrees C and 7 MPa in our experimental conditions) and depends on the plastic amount/KOH volume ratio. The antimony oxide synergist from HIPS-Br remains in recovered plastic during treatment. A pictorial imagination of the proposed debromination process is presented.

Alkalies↗
PubMed2004

Protein separation with surfactant-coated polystyrene involving Cibacron Blue 3GA-conjugated triton X-100.

Through mixing of porous polystyrene particles (Amberlite XAD-4), non-ionic surfactants, and surfactant-conjugated substrates (affinity ligand) in an aqueous solution led to the formation of a novel medium (affinity admicelle) for protein separation. The ligand (CB-Triton) was synthesized by mixing a triazine dye (Cibacron Blue 3GA (CB)) and a polyoxyethylene-type non-ionic surfactant (Triton X-100) in weakly alkaline solutions. Triton X-100 and CB-Triton were competitively sorbed onto XAD-4. Albumin (bovine serum), alcohol dehydrogenase (yeast), and lysozyme (chicken egg) having specific interaction to CB were collected onto the affinity admicelle. On the other hand, the collection of ovalubmin (chicken egg white), having no binding ability to CB, was negligibly small. Lysozyme in 100 microl of chicken egg white, diluted with 900 microl of 10 mM Tris-HCl (pH 7.4), was successfully collected on 18 mg of CB-Triton admicelles and, then, it was eluted with 1 ml of aqueous solution of 100 mM phosphate (pH 7.4). The recovery based on the activity for the lysis of micrococcus and the concentration factor were 60% and 40 (n = 3), respectively.

Micelles↗
PubMed2005

Molecular differences between deuterated and protonated polystyrenes using reversed-phase high-performance liquid chromatography.

Isotopic substitution is a technique used to highlight particular bonds within a molecule for kinetic, spectroscopic and structure analysis. It is presumed that although some properties such as stretching frequencies will not be the same for substituted analogues, the chemical interactions will not vary appreciably as a function of labelling. Reversed-phase liquid chromatography has been used to demonstrate that there are significant differences between the chromatographic behaviour of a sequence of deuterated and protonated oligomeric polystyrenes. Two-dimensional reversed-phase liquid chromatography was used to show that even the diasteromers of the oligomers (n = 5) have retention mechanisms that are dependent on the subtle changes to the molecular conformation and electronic structure, which are a consequence of deuteration.

Chromatography, High Pressure Liquid↗
PubMed2005

Determination of bromophenols as dioxin precursors in combustion gases of fire retarded extruded polystyrene by sorptive sampling-capillary gas chromatography-mass spectrometry.

Extruded polystyrene (XPS) is often treated with hexabromocyclododecane (HBCD) as fire retardant (FR). Because of its aliphatic structure, HBCD is not suspected to cause formation of polybrominated dioxins upon combustion. Precursors of polybrominated dioxins, namely bromophenols, were detected during tubular furnace combustion experiments of FR-XPS in combination with sorptive enrichment on polydimethylsiloxane followed by on-line thermal desorption-capillary GC/MS. The highest concentration of mono- and tribromophenols detected were 85.9 and 3.7 mg kg(-1), respectively, at a temperature of 700 degrees C, while a temperature of 500 degrees C yielded the highest concentration of dibromophenols namely 10.4 mg kg(-1). At a combustion temperature of 900 degrees C no bromophenols were detected.

Dioxins↗
PubMed2005

Preparative frontal size-exclusion chromatography of mineral ions on neutral hypercrosslinked polystyrene.

Hypercrosslinked polystyrene, being the first and the only one accessible for water microporous hydrophobic polymeric sorbent, was found to provide efficient separation of inorganic electrolytes under conditions of a frontal size-exclusion chromatography (SEC). The process, based on the difference in size of hydrated competing ions, permits separations of many pairs of salts, acids, and bases. The productivity of separation increases with the concentration of the feed solution rising. Remarkably, concentrations of the separated components in corresponding fractions may substantially exceed those in the initial mixture, which can be explained in terms of a conception of an ideal separation process.

Anions↗
PubMed2005

Selectivity in preparative separations of inorganic electrolytes by size-exclusion chromatography on hypercrosslinked polystyrene and microporous carbons.

Preparative-scale separation of concentrated solutions of simplest mineral electrolytes by size-exclusion chromatography was performed on three samples of commercially available microporous hypercrosslinked polystyrene sorbents "Macronet Hypersol" and two experimental samples of activated carbons. Selectivity of separation of a pair of electrolytes was found to be determined by the largest ions in each pair. Fortunately, selectivity rises at higher concentrations of electrolytes, which was explained by exclusion of smaller species from the concentrated solution, i.e., mobile phase, into small pores of the column packing that are inaccessible to large species. The separation of concentrated mixtures revealed another remarkable advantage of the new process - self-concentrating of each of two separated components in the corresponding fractions. Self-concentration is more pronounced for the minor component that occupied less space in the initial mixture. The new method may prove productive in processing pickle bath solutions.

Carbon↗
PubMed2005

Direction of temperature gradient for normal-phase temperature gradient interaction chromatography in polystyrene fractionation.

Temperature gradient interaction chromatography (TGIC) is a powerful technique for molecular weight fractionation of polymers, in which the interaction strength is controlled by varying the column temperature. In the present paper, the effects of the sign of the temperature dependence of the retention and the direction of the temperature gradient (raising or lowering) on TGIC in the normal-phase mode were studied for the molecular weight fractionation of polystyrene samples in organic mobile phases. It was found that a positive temperature gradient was effective in the system consisting of amino-modified silica (NH(2)) column and the eluent mixture of tetrahydrofuran and n-hexane where retention decreased with increasing temperature. A negative temperature gradient was effective for the systems consisting of a bare-silica column//chloroform/n-hexane and NH(2)-column//chloroform/n-hexane, where retention increased with increasing temperature. Increasing retention with increasing temperature has been found, so far, only for a water-soluble polymer (PEO) in an aqueous mobile phase in RP-TGIC.

Chromatography, High Pressure Liquid↗
PubMed2005

Solid phase extraction of some precious metals from hydrochloric acid to polystyrene-divinylbenzene porous resin impregnated with polyoxyethylene-type nonionic surfactant.

The solid phase extraction of gold(III), platinum(II), and palladium(II) to surfactant-impregnated polystyrene-divinylbenzene porous resin (XAD-4) was studied. The extracting media could be prepared just by mixing the resin in aqueous surfactant solutions. XAD-4 impregnated with a nonionic surfactant, polyethylene glycol monooleyl ether, was useful for extracting gold(III) from hydrochloric acid. The extractions of platinum(II) and palladium(II) were improved in the use of XAD-4 impregnated with a nitrogen-containing nonionic surfactant, polyethylene glycol stearyl amine. On the other hand, base metals such as copper(II), cobalt(II), nickel(II) and zinc(II), were hardly extracted.

Chemistry Techniques, Analytical↗