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Query: UMLS:C0036421 (PSS)
 10,989 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Organic thin film transitors (TFTs) with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, as the active layer and cross-linked, layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) multilayers as the gate dielectric layer were investigated. A combination of spectroscopic data and device performance characteristics was used to study the behavior of these TFT devices under a variety of controlled environmental test conditions. It was shown that depletion and recovery of the device can be induced to occur by a means that is consistent with the electrochemical oxidation and reduction of water contained in the film. In addition to acting as a reactant, moisture also acts as a plasticizer to control the mobility of other species contained in the film and thereby permits bistable operation of these devices. Raman spectroscopy was used to show that the observed device switching behavior is due to a change in the PEDOT doping level.
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PMID:Bistability in doped organic thin film transistors. 1769 84

Multilayer films containing microgels of chemically cross-linked poly(allylamine hydrochloride) (PAH) and dextran (named PAH-D) were fabricated by layer-by-layer deposition of PAH-D and poly(styrene sulfonate) (PSS). The successful fabrication of PAH-D/PSS multilayer films was verified by quartz crystal microbalance measurements and cross-sectional scanning electron microscopy. The as-prepared PAH-D/PSS multilayer films can reversibly load and release negatively charged dyes such as methyl orange (MO) and fluorescein sodium and mercaptoacetic acid-stabilized CdTe nanoparticles. The loading capacity of the film for MO can be as large as approximately 3.0 microg/cm2 per bilayer, which corresponds to a MO density of 0.75 g/cm3 in the film. The high loading capacity of the PAH-D/PSS films originates from the cross-linked film structure with sufficient binding groups of protonated amine groups, as well as their high swelling capability by solvent. The loaded material can be released slowly when immersing the films in 0.9% normal saline. Meanwhile, the PAH-D/PSS multilayer films could deposit directly on either hydrophilic or hydrophobic substrates such as quartz, polytetrafluoroethylene, polystyrene, poly(ethylene terephthalate), and polypropylene. The microgel films of PAH-D/PSS are expected to be widely useful as matrixes for loading functional guest materials and even for controlled release.
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PMID:Layer-by-layer assembled microgel films with high loading capacity: reversible loading and release of dyes and nanoparticles. 1820 23

Template directed Layer-by-layer (LbL) technology recently moved into the center of scientific attention, particularly as a versatile tool for bioencapsulation purposes. Its major advantages can be found in the striking simplicity of tuning wall properties and the complete control over layer thickness and permeability. Yet, for the most commonly applied pair of polyelectrolytes, poly(allylamine) hydrochloride (PAH) and poly(styrene sulfonate) sodium salt (PSS), the mandatory control of the successful deposition on plane and colloidal surfaces is currently only attainable by means of sophisticated and expensive equipment. Here we describe an alternative quantification method based on a simple colorimetric assay using the Bradford reagent, a cost-effective commercially available dye, and standard laboratory technical devices. The binding of the dye to PSS causes a distinct shift of the absorption maximum from 465 to 680 nm, providing a method for spectral quantification of submicrogram amounts of dissolved PSS during LbL coating with significant accuracy and excellent reproducibility. The method was successfully employed to quantify accurate polyelectrolyte loadings on several particles that have a general importance as LbL templates. Thus, this method can be recommended as standard laboratory technique for control of LbL encapsulation and will considerably broaden the applicability of this promising technology in biotechnology.
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PMID:Colorimetric assay for sensitive poly(styrene sulfonate) quantification in a template directed polyelectrolyte-assembling process. 1821 61

Since systemic sclerosis (SSc) also involves the heart, the aim of the present study was to evaluate possible differences in right ventricular (RV) pump function between SSc-associated pulmonary arterial hypertension (PAH; SScPAH) and idiopathic PAH (IPAH). In 13 limited cutaneous SScPAH and 17 IPAH patients, RV pump function was described using the pump function graph, which relates mean RV pressure ((RV)) and stroke volume index (SVI). Differences in pump function result in shift or rotation of the pump function graph. (RV) and SVI were measured using standard catheterisation. The hypothetical isovolumic (RV) ((RV,iso)) was estimated using a single-beat method. The pump function graph was approximated by a parabola: (RV) = (RV,iso)[1-(SVI/SVI(max))(2)], where SVI(max )is the hypothetical maximal SVI at zero (RV), enabling calculation of SVI(max). There were no differences in SVI and SVI(max). Both (RV) and (RV,iso) were significantly lower in SScPAH than in IPAH ((RV) 30.7+/-8.5 versus 41.2+/-9.4 mmHg; (RV,iso) 43.1+/-12.4 versus 53.5+/-10.0 mmHg). Since higher pressures were found at similar SVI, the difference in the pump function graph results from lower contractility in SScPAH than in IPAH. Right ventricular contractility is lower in systemic sclerosis-associated pulmonary arterial hypertension than in idiopathic pulmonary arterial hypertension.
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PMID:Right ventricular contractility in systemic sclerosis-associated and idiopathic pulmonary arterial hypertension. 1821 49

Gold nanoparticles of 5 nm diameter, stabilized by 4-(dimethylamino)pyridine (DMAP), were coated with poly(sodium 4-styrene sulfonate) (PSS) via electrostatic self-assembly. The suspension stability, monitored by the gold surface plasmon band (SPB), was studied by varying the pH, the PSS chain length, and PSS concentration. Enhanced stability is obtained at pH 10 (above the pKa of DMAP) when the polymer chain length matches or exceeds the particle circumference. Solid state 13C NMR was used to determine the presence of DMAP and polymers after subsequent deposition of weak and strong polycations: poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDADMAC). At pH 10, DMAP remains associated with the nanoparticle after the first PSS layer has been formed. When PAH or PDADMAC are subsequently added at pH 4.5, DMAP is expelled, the suspensions remain stable, and zeta potential values indicate complete charge reversal. In the case of PDADMAC, however, the first layer of PSS is not fully retained. When PDADMAC is added at pH 10, DMAP and the first PSS layer are retained but lower zeta potentials and a higher SPB shift indicate a degraded stability. For PAH addition at pH 9.5, both DMAP and PSS are expelled and the suspension becomes unstable. These differences in stability of the multilayer components and the nanoparticle suspension are rationalized in terms of chain flexibility, polymer charge density, and the ability of the polymer functional groups to directly interact with the gold surface.
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PMID:Preparation and characterization of polyelectrolyte-coated gold nanoparticles. 1822 59

We studied the influence of post-treatment rinsing after the formation of self-assembled polyelectrolyte films made with the weak base poly(allylamine hydrochloride) (PAH) and the strong acid poly(styrene sulfonate) (PSS). The stability of the film was studied using optical fixed-angle laser reflectometry to measure the release of polymeric material and AFM experiments to reveal the change of morphology and thickness. We found that the polymer films were stable upon rinsing when the pH was the same in the solution as that used in the buildup (pH 9). The films released most of the polymeric material when rinsed at higher pH values, but a layer remained that corresponded to a PAH monolayer directly bound with the silica surface. Films containing at least four bilayers were stable upon rinsing at lower pH values, but the stability of thinner films depended on the type of the last polymer deposited. They were stable in the case of PSS as an outermost deposit, but they released a large part of their material in the case of PAH. The stability results were determined using a simple model of the step-by-step assembly of the polymer film described formerly.
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PMID:Stability of self-assembled polymer films investigated by optical laser reflectometry. 1827 36

Systemic sclerosis is a generalized autoimmune connective tissue disease of unknown aetiology. Profound vascular and immunological dysregulations result in tissue fibrosis affecting the skin and internal organs. Currently, two main clinical subtypes are distinguished, i.e. limited and diffuse cutaneous systemic sclerosis, which differ significantly in the clinical course and prognosis. Autoantibodies against topoisomerase (Scl-70), centromere-associated proteins, and nucleolar antigens are important for the diagnosis of the disease and give clues for its clinical manifestations and prognosis (prognostic autoantibodies). For most of these antibodies, however, the role in pathogenesis is not established. Anti-centromere antibodies are associated with limited cutaneous involvement and risk for pulmonary hypertension, whereas anti-topoisomerase I is associated with diffuse progressive disease and severe interstitial lung disease. Anti-Th/To positivity is associated with limited skin involvement but a high risk for severe internal organ involvement (Kidneys, PAH, Lung fibrosis). Anti-RNA polymerase I/III antibodies are associated with a high risk for renal involvement. Autoantibodies against the PDGF receptor and fibrillin-1 seem to play important roles in the pathogenetic process of systemic sclerosis.
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PMID:Autoantibodies in systemic sclerosis (scleroderma): clues for clinical evaluation, prognosis and pathogenesis. 1828 46

Conventional alginate/poly-L-ornithine (AP) membranes used to immunoisolate foreign tissue transplants fail in long-term transplantations of immortal cell lines. We have developed a novel layer-by-layer (LbL) membrane using polystyrene sulfonate and polyallylamine hydrochloride (PSS/PAH) on top of the coherent AP membrane. Assembly of the LbL membrane was followed by electrophoresis, and the surface morphologies and structure were characterized and examined by cryo-scanning electron microscope and transmission electron microscopy. Unlike the standard AP membrane, the LbL membrane withstood the internal pressure generated by continuous cell proliferation of microencapsulated HEK-293 and Min-6 cells. The new membrane did not affect insulin secretion or diffusion by Min-6 cells.
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PMID:Assembly of multilayer PSS/PAH membrane on coherent alginate/PLO microcapsule for long-term graft transplantation. 1828 25

Polyelectrolyte multilayers (PEMs) formed at interfaces between aqueous solutions and thermotropic (water-immiscible) liquid crystals (LCs) offer the basis of a new method to tailor the nanometer-scale structure and chemical functionality of these interfaces. Toward this end, we report a study that compares the growth of PEMs formed at mobile and deformable interfaces defined by LCs relative to growth observed at model (rigid) solid surfaces. Experiments aimed at determining if polyelectrolytes such as poly(sodium-4-styrenesulfonate) (PSS) can partition from the aqueous phase into the bulk of the LC yielded no evidence of such partitioning. Whereas measurements of the growth of PEMs formed from poly(allylamine hydrochloride) (PAH) and PSS at the aqueous-LC interface revealed growth characteristics similar to those measured at both hydrophobic and hydrophilic interfaces of solids, the growth of PEMs from PAH and poly(acrylic acid) (PAA) at the aqueous-LC interface was found to differ substantially from the solids investigated: (i) the linear growth of PEMs of PAH/PAA that was measured at the aqueous-LC interface under conditions that did not lead to the growth of PEMs at the interface of octadecyltrichlorosilane (OTS)-treated glass (a hydrophobic solid surface), and (ii) in comparison to the growth of PEMs of PAH/PAA at the surface of glass (a hydrophilic charged surface), a higher rate of growth was observed at the aqueous-LC interface. The finding that the growth rate of PEMs of PAH/PAA at aqueous-LC interfaces is greater than on solid surfaces is supported by additional measurements of growth as a function of pH. Finally, the pH-triggered reorganization of PAH/PAA PEMs supported at the aqueous-LC interface led to changes in the order and optical properties of the LC. These data are discussed in light of the nature of aqueous-LC interfaces, including the mobility and deformability of the interface and recent measurements of the zeta-potentials of aqueous-LC interfaces.
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PMID:Characterization of the growth of polyelectrolyte multilayers formed at interfaces between aqueous phases and thermotropic liquid crystals. 1841 43

Liquid cell atomic force microscopy (LC-AFM) is used to image self-assembled polyelectrolyte films eliminating any drying effects on the film structure. Weak/weak and strong/weak polyelectrolyte films are formed by the alternated deposition of poly(acrylic acid) [PAA]/poly(allylamine hydrochloride) [PAH], and poly(sodium 4-styrene sulfonate) [PSS]/PAH, respectively, forming a granular surface structure. Number and area of grains (GN, GA) are used to characterize the surface of these films during their build up process. We show that hydrophilic PAA increases GA and decreases GN, while these parameters follow an opposite behavior with PSS. In both cases, GA and GN always have a simple inverse relationship, and then grain surface coverage (GS=GNGA) is nearly constant and independent of polyelectrolyte nature and the substrates used here, but also in the published data as well. The drying of the weak/weak film was also imaged after natural and forced solvent evaporation, and the surface structure is strongly affected, although the GS values keep roughly the same value found for wet films. The set of these results indicates that GS may be considered as a constant parameter during the build-up for the self-nascent assembled polyelectrolytes. The granular structure is still maintained after glucose oxidase adsorption on these films with comparable GS values.
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PMID:Granular structure of self-assembled PAA/PAH and PSS/PAH nascent films imaged in situ by LC-AFM. 1844 87


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