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PubMed2005

Inorganic oxide core, polymer shell nanocomposite as a high K gate dielectric for flexible electronics applications.

Organic/inorganic core shell nanoparticles have been synthesized using high K TiO(2) as the core nanoparticle, and polystyrene as the shell. This material is easy to process and forms transparent continuous thin films, which exhibit a dielectric constant enhancement of over 3 times that of bulk polystyrene. This new dielectric material has been incorporated into capacitors and thin film transistors (TFTs). Mobilities approaching 0.2 cm(2)/V.s have been measured for pentacene TFTs incorporating the new TiO(2) polystyrene nanostructured gate dielectric, indicating good surface properties for pentacene film growth. This novel strategy for generating high K flexible gate dielectrics will be of value in improving organic and flexible electronic device performance.

Electronics↗
PubMed2005

Development and characterization of a high-throughput system for assessing cell-surface receptor-ligand engagement.

A nonfouling interfacial interpenetrating polymer network (IPN) of poly(acrylamide-co-ethylene glycol/acrylic acid) [p(AAm-co-EG/AAc)] was grafted to polystyrene for use as a novel platform for the development of high-throughput assays for screening of specific bimolecular interactions (i.e., receptor-ligand engagement). For the development of the IPN, a water-soluble hydrogen-abstracting photoinitiator was investigated: (4-benzoylbenzyl)trimethylammonium chloride. IPN-modified polystyrene surfaces were characterized using XPS, contact angle goniometry, and protein adsorption analysis. These IPN surfaces minimized fibrinogen adsorption compared to tissue culture polystyrene (>96% reduction), prevented mammalian cell adhesion, and served as nonfouling surfaces to graft biological ligands. For bimolecular interaction studies, a model peptide ligand from bone sialoprotein (Ac-CGGNGEPRGDTYRAY-NH(2)) was grafted to p(AAm-co-EG/AAc) via a 3400 M(w) linear pEG spacer. Ligand density measurements, cell culture, and a centrifugal adhesion assay were used to study cell adhesion to peptide-modified IPNs (i.e., receptor-ligand engagement). Ligand density (Gamma) was controllable from approximately 1 to 20 pmol/cm(2) by modulating the peptide input concentration (0.02-20 microM). Cell adhesion was directly dependent on the ligand density. This technology creates a powerful high-throughput system to simultaneously probe a myriad of cell-surface receptor-ligand interactions.

Cell Adhesion↗
PubMed2005

Active loading and tunable release of doxorubicin from block copolymer vesicles.

Vesicles are spherical bilayers that offer a hydrophilic reservoir, suitable for the incorporation of water-soluble molecules, as well as a hydrophobic wall that protects the loaded molecules from the external solution. The permeability of a vesicle wall made from polystyrene can be enhanced by adding a plasticizer such as dioxane. Tuning the wall permeability allows loading and release of molecules from vesicles to be controlled. In this study, vesicles are prepared from polystyrene(310)-b-poly(acrylic acid)(36) and used as model carriers for doxorubicin (DXR), a weak amine and a widely used anticancer drug. To increase the wall permeability, different amounts of dioxane are added to the vesicle solution. A pH gradient is created across the vesicle wall (inside acidic) and used as an active loading method to concentrate the drug inside the vesicles. The results show that a pH gradient of ca. 3.8 units can enhance the loading level up to 10-fold relative to loading in the absence of the gradient. After loading, the release of DXR from vesicles is followed as a function of the wall permeability. The diffusion coefficient of doxorubicin through polystyrene (D) is evaluated from the initial slope of the release curves; the value of D ranges from 8 x 10(-17) to 6 x 10(-16) cm(2)/s, depending on the degree of plasticization of the vesicle wall.

Antibiotics, Antineoplastic↗
PubMed2005

Establishment and implications of a characterization method for magnetic nanoparticle using cell tracking velocimetry and magnetic susceptibility modified solutions.

Magnetic micro and nanoparticles conjugated to affinity labels have become a significant, commercial reagent. It has been demonstrated that the performance of cell separation systems using magnetic labels is a function of the magnitude of the magnetic force that can be generated through labeling. This magnetic force is proportional to the number of magnetic particles bound to the cell, the magnetic energy gradient, and the particle-field interaction parameter. This particle-field interaction parameter, which is the product of the relative volumetric, magnetic susceptibility and the volume of the micro or nanoparticle, is a fundamental parameter which can be used to characterize the magnetic particles. An experimental technique is presented which measures the volumetric magnetic susceptibility of particles through the use of susceptibility modified solutions and an experimental instrument, Cell Tracking Velocimetry, CTV. Experimental studies were conducted on polystyrene microspheres alone and those bound to four different magnetic nanoparticles. The experimentally determined values of the magnetic susceptibility of the polystyrene microspheres are consistent with values found from literature. Consequently, magnetic susceptibility measurements of these polystyrene microspheres bound with the magnetic nanoparticles combined with particle size measurements using commercial dynamic light scattering instrument allowed estimates of the particle-field interaction parameter to be made for four commercial, magnetic nanoparticles. The value found for MACS beads is close to what is reported from an independent study. The values for MACS beads and Imag beads are found to agree with what is observed from experiments. Finally, an experimental demonstration of the impact that differences in this field interaction parameter has on the labeling of human lymphocytes is presented.

Cell Movement↗
PubMed2005

Microparticle sampling by electrowetting-actuated droplet sweeping.

This paper describes a new microparticle sampler where particles can be efficiently swept from a solid surface and sampled into a liquid medium using moving droplets actuated by the electrowetting principle. We successfully demonstrate that super hydrophilic (2 microm and 7.9 microm diameter glass beads of about 14 degrees contact angle), intermediate hydrophilic (7.5 microm diameter polystyrene beads of about 70 degrees contact angle), and super hydrophobic (7.9 microm diameter Teflon-coated glass beads and 3 microm size PTFE particles of over 110 degrees contact angles) particles on a solid surface are picked up by electrowetting-actuated moving droplets. For the glass beads as well as the polystyrene beads, the sampling efficiencies are over 93%, in particular over 98% for the 7.9 microm glass beads. For the PTFE particles, however, the sampling efficiency is measured at around 70%, relatively lower than that of the glass and polystyrene beads. This is due mainly to the non-uniformity in particle size and the particle hydrophobicity. In this case, the collected particles staying (adsorbing) on the air-to-water interface hinder the droplet from advancing. This particle sampler requires an extremely small amount of liquid volume (about 500 nanoliters) and will thus be highly compatible and easily integrated with lab-on-a-chip systems for follow-up biological/chemical analyses.

Glass↗
PubMed1999

Adsorption of EGF receptor ligands to test tubes--a factor with implications for studies on the potency of these peptides.

Studies on the relative potency of ligands for the epidermal growth factor receptor are usually performed with highly purified ligand specimens. However, adsorption of ligands to glass and plastic surfaces may affect the results by reducing the ligand concentration in an unpredictable way. The aim of this study was to examine the adsorption of four epidermal growth factor (EGF) receptor ligands, EGF, transforming growth factor alpha (TGF-alpha), heparin binding-EGF (HB-EGF) and betacellulin, to commonly used test tubes of polyethylene, polystyrene and glass, respectively. The ligands were kept in a sodium phosphate buffer, both with and without 0.1% human albumin as carrier protein. Adsorption was examined after 20 minutes at room temperature as well as after overnight storage at 4 degrees C. The ligands were quantitated by ELISAs. In the buffer not containing 0.1% human albumin there was a marked adsorption, which differed both among the ligands and among the test tubes. After 20 minutes the ligand concentrations were reduced to 33-73% in polyethylene tubes, to 15-46% in polystyrene tubes and to 12-29% in glass tubes. The adsorption was even more pronounced after storage overnight. The use of 0.1% human albumin in the buffer solved the problem in polyethylene and polystyrene tubes, but not in glass tubes. The results demonstrate that adsorption to surfaces can be a significant problem for EGF receptor ligands and emphasize the need for controlling the growth factor concentration in the final experimental setting.

Adsorption↗
PubMed2005

Monte Carlo- versus pencil-beam-/collapsed-cone-dose calculation in a heterogeneous multi-layer phantom.

The aim of this work was to evaluate the accuracy of dose predicted in heterogeneous media by a pencil beam (PB), a collapsed cone (CC) and a Monte Carlo (MC) algorithm. For this purpose, a simple multi-layer phantom composed of Styrofoam and white polystyrene was irradiated with 10 x 10 cm2 as well as 20 x 20 cm2 open 6 MV photon fields. The beam axis was aligned parallel to the layers and various field offsets were applied. Thereby, the amount of lateral scatter was controlled. Dose measurements were performed with an ionization chamber positioned both in the central layer of white polystyrene and the adjacent layers of Styrofoam. It was found that, in white polystyrene, both MC and CC calculations agreed satisfactorily with the measurements whereas the PB algorithm calculated 12% higher doses on average. By studying off-axis dose profiles the observed differences in the calculation results increased dramatically for the three algorithms. In the regions of low density CC calculated 10% (8%) lower doses for the 10 x 10 cm2 (20 x 20 cm2) fields than MC. The MC data on the other hand agreed well with the measurements, presuming that proper replacement correction for the ionization chamber embedded in Styrofoam was performed. PB results evidently did not account for the scattering geometry and were therefore not really comparable. Our investigations showed that the PB algorithm generates very large errors for the dose in the vicinity of interfaces and within low-density regions. We also found that for the used CC algorithm large deviations for the absolute dose (dose/monitor unit) occur in regions of electronic disequilibrium. The performance might be improved by better adapted parameters. Therefore, we recommend a careful investigation of the accuracy for dose calculations in heterogeneous media for each beam data set and algorithm.

Algorithms↗
PubMed1987

Platinum-shadowed, whole-mounts for transmission electron microscopy of cells cultured on plastic.

A simple and convenient method is described whereby cells cultured on polystyrene plastic substrata may be critical point-dried, rotary-shadowed with platinum/carbon and finally released by means of propylene oxide for examination whole in the transmission electron microscope. The technique is particularly useful for the localization of colloidal gold probes, both intra- and extra-cellularly. The problem of premature melting of polystyrene at about 307 K after prolonged exposure to carbon dioxide is solved by limiting the residence time in the critical point-drier to 1 h. Details for cleaning and mounting the released films of cells on specimen grids are given. The technique expands the application of the 'whole-mount' approach of Hopkins and co-workers (Hopkins et al., 1981; Hopkins, 1985) to cells cultured directly on polystyrene substrata, that is, in conventional plastic culture vessels.

Animals↗
PubMed2007

Behavior of CAL72 osteoblast-like cells cultured on zirconia ceramics with different surface topographies.

OBJECTIVES: Because of its inherent strength, biocompatibility, and tooth-like color, zirconia ceramics have the potential to become an alternative to titanium as dental implant material. This study aimed at investigating the osteoblastic response to yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) with different surface topographies. METHODS: CAL72 osteoblast-like cells were cultured on machined (TZP-m), airborne particle abraded (TZP-s), and airborne particle abraded and acid-etched Y-TZP (TZP-sa) surfaces. Polystyrene and airborne particle abraded with large grit and acid-etched (SLA) titanium served as a reference control. The surface topography was examined by scanning electron microscopy (SEM) and profilometry. At culture days 3, 6, and 12, cell proliferation, at day 12 cell morphology, and cell-covered surface area were determined. RESULTS: The surface roughness of Y-TZP was increased by airborne particle abrasion and additionally by acid etching. No statistically significant differences were found between average roughness (R(a)) and maximum peak-to-valley height (R(p-v)) values of airborne particle abraded and acid-etched Y-TZP and SLA titanium. Whereas the cell proliferation assay revealed statistically significant greater values at day 3 for surface-treated Y-TZP and polystyrene cultures as compared with machined Y-TZP, no differences between the Y-TZP groups, SLA titanium, and polystyrene were observed at culture days 6 and 12. CONCLUSIONS: Cell morphology and cell-covered surface area were not affected by the type of substrate. The results suggest that roughened Y-TZP is an appropriate substrate for the proliferation and spreading of osteoblastic cells.

Acid Etching, Dental↗
PubMed1986

Influence of substratum hydration and adsorbed macromolecules on bacterial attachment to surfaces.

The attachment of Pseudomonas fluorescens and an Acinetobacter sp. to hydrogel and polystyrene surfaces was investigated to evaluate the influence of adsorbed water and macromolecules on adhesion. With both organisms, there was a decrease in attachment numbers with increasing water content of the hydrogels. There was also a decrease in attachment with a decrease in water contact angle on untreated, tissue culture and sulfonated polystyrene surfaces; however, the attachment numbers were higher than would be expected on the basis of the hydrogel data. With P. fluorescens, attachment to untreated and tissue culture polystyrene was inhibited by bovine serum albumin, Escherichia coli lipopolysaccharide, and the supernatant from spent medium, both when the conditioning substances were added to the suspension of attaching cells and when they were preadsorbed onto the surfaces. Dextran inhibited attachment only when added to the bacterial suspension. Supernatants from centrifuged natural freshwater samples had no effect. Thus, hydration of a surface and the adsorption of macromolecules can reduce bacterial attachment; however, additional factors relating to the chemical composition of the substratum and polymeric stabilization of suspended cells can affect the adhesion interaction and resultant numbers of attached cells.

Acinetobacter↗
PubMed1982

Whole-bacterial cell enzyme-linked immunosorbent assay for Streptococcus sanguis fimbrial antigens.

A whole-bacterial cell enzyme-linked immunosorbent assay (bactELISA) was developed for detecting fimbrial antigens on Streptococcus sanguis. In this assay, S. sanguis cells were directly adhered to polystyrene or polyvinyl via drying. Use of the assay indicated that consistently high and uniform optical densities could be obtained from well to well. In addition, radioactive assaying indicated increased adsorption to the polystyrene wells over polyvinyl, suggesting that polystyrene may prove superior in the gram-positive bactELISA. Use of the bactELISA may prove valuable to both the clinical and research laboratory involved in the study of bacterial cell surface components or in the evaluation of antisera directed against bacterial antigens, which are difficult to prepare as purified derivatives.

Antigens, Bacterial↗
PubMed2003

Indole can act as an extracellular signal to regulate biofilm formation of Escherichia coli and other indole-producing bacteria.

We demonstrated previously that genetic inactivation of tryptophanase is responsible for a dramatic decrease in biofilm formation in the laboratory strain Escherichia coli S17-1. In the present study, we tested whether the biochemical inhibition of tryptophanase, with the competitive inhibitor oxindolyl-L-alanine, could affect polystyrene colonization by E. coli and other indole-producing bacteria. Oxindolyl-L-alanine inhibits, in a dose-dependent manner, indole production and biofilm formation by strain S17-1 grown in Luria-Bertani (LB) medium. Supplementation with indole at physiologically relevant concentrations restores biofilm formation by strain S17-1 in the presence of oxindolyl-L-alanine and by mutant strain E. coli 3714 (S17-1 tnaA::Tn5) in LB medium. Oxindolyl-L-alanine also inhibits the adherence of S17-1 cells to polystyrene for a 3-h incubation time, but mutant strain 3714 cells are unaffected. At 0.5 mg/mL, oxindolyl-L-alanine exhibits inhibitory activity against biofilm formation in LB medium and in synthetic urine for several clinical isolates of E. coli, Klebsiella oxytoca, Citrobacter koseri, Providencia stuartii, and Morganella morganii but has no affect on indole-negative Klebsiella pneumoniae strains. In conclusion, these data suggest that indole, produced by the action of tryptophanase, is involved in polystyrene colonization by several indole-producing bacterial species. Indole may act as a signalling molecule to regulate the expression of adhesion and biofilm-promoting factors.

Alanine↗
PubMed2006

Molecular aspects of microparticle phagocytosis by dendritic cells.

The ability of immature dendritic cells (iDCs) derived from human peripheral blood mononuclear cells to phagocytose poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) as compared to polystyrene MPs and the molecular aspects of this phagocytosis were investigated. Treating iDCs with PLGA or polystyrene fluorospheres of approximately 3 microm in diameter resulted in the internalization of the particles as evidenced by confocal laser scanning micrographs. This uptake of fluorospheres by DCs was decreased by pretreatment of cells with cytochalasin D or by incubation with the fluorospheres at 4 degrees C, and was sensitive to EDTA and trypsin pretreatments in a dose-dependent manner. In agreement with our previous studies, treatment of iDCs with PLGA MPs, but not with polystyrene MPs, led to DC maturation, as measured by increase in release of the autocrine maturation cytokine, tumor necrosis factor-alpha, which was dependent on ratio of PLGA MPs to DCs. Taken together, this work begins to address the role of phagocytosis on PLGA MP-induced DC maturation and the molecular mechanisms involved.

Biocompatible Materials↗
PubMed1994

Receptor-mediated regulation of differentiation and proliferation of hepatocytes by synthetic polymer model of asialoglycoprotein.

Morphology and responses of hepatocytes are investigated using an artificial asialoglycoprotein model polymer--lactose-carrying polystyrene (PVLA) as a culture substratum, especially in focusing on the effect of the surface density of the PVLA substratum. The surface density of PVLA on polystyrene dishes was determined using fluorescein-labeled PVLA as a probe under a fluorescence laser microscope. PVLA-coated surfaces were observed by scanning electron microscope and atomic force microscopies under air and water, which showed that PVLA molecules were adsorbed patchily on low density surfaces and uniformly concentrated all over the dish on high density surfaces. It is suggested from the requirement of the Ca2+ ion, inhibition of galactosyl substances, and localization of receptors that the adhesion of hepatocytes to both low and high PVLA-density surfaces is mediated by galactose-specific interactions between PVLA and asialoglycoprotein receptors. At low PVLA densities (0.07 micrograms cm-2), the hepatocytes were flat and expressed high levels of 3H-thymidine uptake and low levels of bile acid secretion. Contrastingly, at high PVLA densities (1.08 micrograms cm-2), they were round and expressed a low level of 3H-thymidine uptake and a high level of bile acid secretion. The shapes, proliferation, and differentiation of hepatocytes could be regulated by varying the densities of PVLA adsorbed to polystyrene dishes. We assume that there are two recognition mechanisms operating between PVLA and hepatocytes: (1) adhesion through highly concentrated or clustered galactose-specific interaction; and (2) responses in shape, proliferation, and differentiation by PVLA-coating densities.

Animals↗
PubMedDate not supplied

Spatial patterning of colloidal nanoparticle-based thin film by a combinative technique of layer-by-layer self-assembly and lithography.

A novel approach to generating clear patterns of different types of nanoparticles is presented in this paper. Nanoassembly in the vertical direction was combined with planar micropatterning. This provides industrial applications of a popular layer-by-layer method to produce multilayers of polymers, nanoparticles, and proteins organized on the nanometer scale. A thin film of organic polystyrene spheres was first coated on the pretreated silicon wafer with layer-by-layer self-assembly. Then a layer of aluminium was deposited on the thin film. A layer of positive photoresist was spun on the surface of aluminum and then illuminated with UV light. The exposed parts of the resist were removed and windows were opened above the aluminum. The subsequent etching removed exposed aluminium and left a polystyrene thin film in the open windows. Oxygen plasma was employed to remove the polystyrene thin film on the bottom. Eventually, aluminum and photoresist were removed and only the desired pattern remained. This approach was also employed for the patterning of the silica nanoparticle thin film, a widely used material in various applications. In this case, wet etching was demonstrated to etch silica particles. A scanning electron microscope was used to produce the image of the pattern.

Aluminum↗
PubMed1985

Ultrastructural study of epithelial cell attachment to implant materials.

Attachment of gingival tissues to the protruding post of an endosseous dental implant is of great importance for the prognosis of its clinical success. Little is known about the requirements an implant material must meet to secure a durable permucosal seal. The objective of this study, therefore, was to gain insight into the morphology of epithelial cell-implant interfaces for a number of well-known or potential implant materials. Guinea pig epithelial cells were cultured on gold, titanium, carbon, hydroxylapatite, carbonate apatite, and modified polystyrene substrates. The metallic and carbon substrates were obtained by vapor-phase deposition of thin films on polystyrene carriers. This technique allowed for the preparation of ultra-thin sections for transmission electron microscopy containing substrate as well as the cells adhering to it. The cultures on apatite were decalcified prior to sectioning. The results revealed tht as attachment structures, focal contacts, extracellular matrix contacts, and hemidesmosome-like contracts could be distinguished. Hemidesmosome-like contacts were only observed on apatite and polystyrene and not on the metallic or carbon surfaces. The results of this study suggest the existence of some, as yet unknown, property of the substrate that determines the nature and the structure of the contact site with epithelial cells.

Animals↗
PubMed2004

Characterization of apatite formed on alkaline-heat-treated Ti.

Alkaline-heat-treated titanium self-forms an apatite surface layer in vivo. The aim of the present study was to materialistically characterize the surface of alkaline-heat-treated titanium immersed in simulated body fluid (AHS-TI) and to examine the differentiation behavior of osteoblasts on AHS-TI. SEM, thin-film XRD, FTIR, and XPS analyses revealed that AHS-TI contained a 1.0- micro m-thick, low-crystalline, and [002] direction-oriented carbonate apatite surface. Human osteoblast-like SaOS-2 cells were cultured on polystyrene, titanium, and AHS-TI, and RT-PCR analyses of osteogenic differentiation-related mRNAs were conducted. On AHS-TI, the expression of bone sialoprotein mRNA was up-regulated as compared with that on polystyrene and titanium (p < 0.05). On AHS-TI, the expression of osteopontin and osteocalcin mRNAs was up-regulated as compared with that on polystyrene (p<0.05). The results indicate that the apatite was bone-like and accelerated the osteogenic differentiation of SaOS-2, suggesting that alkaline-heat treatment might facilitate better integration of titanium implants with bone.

Alkalies↗
PubMed2005

Molecular and biomechanical characterization of mineralized tissue by dental pulp cells on titanium.

The application of implant therapy is still limited, because of various risk factors and the long healing time required for bone-titanium integration. This study explores the potential for osseointegration engineering with dental pulp cells (DPCs) by testing a hypothesis that DPCs generate mineralized tissue on titanium. DPCs extracted from rat incisors positive for CD44, alkaline phosphatase activity, and mineralizing capability were cultured on polystyrene and on machined and dual-acid-etched (DAE) titanium. Tissue cultured on titanium with a Ca/P ratio of 1.4 exhibited plate-like morphology, while that on the polystyrene exhibited fibrous and punctate structures. Tissues cultured on titanium were harder than those on polystyrene, 1.5 times on the machined and 3 times on the DAE. Collagen I, osteopontin, and osteocalcin genes were up-regulated on titanium, especially the DAE surface. In conclusion, DPCs showing some characteristics of the previously identified dental pulp stem cells can generate mineralized tissue on titanium via the osteoblastic phenotype, which can be enhanced by titanium surface roughness.

Acid Etching, Dental↗