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Query: UMLS:C1832588 (PSS)
 2,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Multilayer nanofilms, formed by the layer-by-layer (LbL) adsorption of positively and negatively charged polyelectrolytes, are promising substrates for tissue engineering. We investigate here the attachment and function of hepatic cells on multilayer films in terms of film composition, terminal layer, rigidity, charge, and presence of biofunctional species. Human hepatocellular carcinoma (HepG2) cells, adult rat hepatocytes (ARH), and human fetal hepatoblasts (HFHb) are studied on films composed of the polysaccharides chitosan (CHI) and alginate (ALG), the polypeptides poly(l-lysine) (PLL) and poly(l-glutamic acid) (PGA), and the synthetic polymers poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS). The influence of chemical cross-linking following LbL assembly is also investigated. We find HepG2 to reach confluence after 7 days of culture on only 2 of 18 candidate multilayer systems: (PAH-PSS)(n) (i.e. nPAH-PSS bilayers) and cross-linked (PLL-ALG)(n)-PLL. Cross-linked PLL-ALG and PLL-PGA films support attachment and function of ARH, independently of the terminal layer, provided collagen is adsorbed to the top of the film. (PAH-PSS)(n), cross-linked (PLL-ALG)(n), and cross-linked (PLL-PGA)(n)-PLL films all support attachment, layer confluence, and function of HFHb, with the latter film promoting the greatest level of function at 8 days. Overall, film composition, terminal layer, and rigidity are key variables in promoting attachment and function of hepatic cells, while film charge and biofunctionality are somewhat less important. These studies reveal optimal candidate multilayer biomaterials for human liver tissue engineering applications.
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PMID:Multilayer nanofilms as substrates for hepatocellular applications. 1865 30

The conjugates of magnetic beads coupled with an antibody can be trapped on the Au film firmly due to the magnetic force for the immunoassay of a surface plasmon resonance (SPR) biosensor. However, this approach exhibits significant limitations in robustness and sensitivity due to incomplete dissociation of magnetic beads from the Au film. The incorporation of a polyelectrolyte film on the Au surface can prevent the magnetic beads from the direct contact with the Au film. The layer-by-layer assembly of polyelectrolyte was used as spacer between the gold surface and the magnetic bead. Different layers of polyelectrolyte can be assembled onto the Au film based on an electrostatic force between polycations and polyanions. After the polyelectrolyte film was fabricated on the Au film, the deposition of the magnetic beads was maintained effectively on the film, which favors the sensitivity of the biosensor and the regeneration of the sensing membrane. When the polyelectrolyte layers of (PAH/PSS)(3) were constructed on the Au film, the SPR biosensor with magnetic beads exhibited a satisfactory response to human IgG in the concentration range from 0.25 to 30.00 microg mL(-1), and the determination limit obtained is eight times lower than that obtained with (PAH/PSS)(1) layer.
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PMID:Improvement of surface plasmon resonance biosensor with magnetic beads via assembled polyelectrolyte layers. 1870 36

A multilayered film was prepared by layer-by-layer (LBL) assembly of active ester modified multiwalled carbon nanotubes (MWCNTs) and poly(allylamine hydrochloride) (PAH). For this purpose, carboxylic groups on the surface of the oxidized MWCNTs were converted to the acyl chlorides by their reaction with thionyl chloride. Subsequent reaction of the acyl chlorides with pentafluorophenol formed the active esters. These active ester modified MWCNTs (MWCNTs-COOC(6)F(5)) were air-stable and moisture resistant, but showed a high reactivity toward primary or secondary amines resulting in amide bonds. For the preparation of a multilayered film, the surface of a quartz slide was first activated and sacrificial double layers of PAH and poly(sodium 4-styrene sulfonate) (PSS) were deposited. Subsequently, LBL assembly of MWCNTs-COOC(6)F(5) and PAH was then conducted on these double layers [(PAH/PSS)2]. In the process of the assembly, a reaction occurred between the active ester on the surface of MWCNTs and the amine groups of polyallylamine yielding amide bonds, which resulted in a mechanically stable thin film. A free-standing film was obtained after dissolving the sacrificial layer [(PAH/PSS)2] in a concentrated aqueous NaOH solution. The surface resistance of the multilayered film with 20 bilayers decreased to around 10 kOmega while remaining a reasonable transparency (70% at 500 nm).
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PMID:Preparation of transparent conductive multilayered films using active pentafluorophenyl ester modified multiwalled carbon nanotubes. 1871 25

The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) platform for multi-parameter sensing is demonstrated by realising EDIS sensors with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration as well as for the label-free electrical monitoring of adsorption and binding of charged macromolecules, like polyelectrolytes. The NCD films were grown on p-Si-SiO(2) substrates by microwave plasma-enhanced chemical vapour deposition. To obtain O-terminated surfaces, the NCD films were treated in an oxidising medium. The NCD-based field-effect sensors have been characterised by means of constant-capacitance method. The average pH sensitivity of the O-terminated NCD film was 40 mV/pH. A low detection limit of 5 microM and a high penicillin G sensitivity of 65-70 mV/decade has been obtained for an EDIS penicillin biosensor with the adsorptively immobilised enzyme penicillinase. Alternating potential changes, having tendency to decrease with increasing the number of adsorbed polyelectrolyte layers, have been observed after the layer-by-layer deposition of polyelectrolyte multilayers, using positively charged PAH (poly (allylamine hydrochloride)) and a negatively charged PSS (poly (sodium 4-styrene sulfonate)) as a model system. The response mechanism of the developed EDIS sensors is discussed.
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PMID:Characterisation of capacitive field-effect sensors with a nanocrystalline-diamond film as transducer material for multi-parameter sensing. 1880 54

Water-dispersible polyelectrolyte multilayers (PEM) were obtained by layer-by-layer assembly of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrene sulfonate) (PSS) on water-soluble poly(ethylene glycol)- graft-multiwalled carbon nanotubes (PEG- g-MWNTs), and their structures were investigated using solution (1)H NMR. It was clearly shown that some segments of the adsorbed topmost layers formed in layer-by-layer assembly processes are still highly mobile in aqueous solution, and these segments are totally compensated by subsequent coatings of the oppositely charged layers to form ionically cross-linked polyelectrolyte complexes (PEC) layers; it was demonstrated that the ionization behaviors of the highly mobile segments of the topmost PAH layers are similar to those in solution rather than those in the bulk multilayers at different pH. Furthermore, the similarity among the PEM on substrates and the PEC colloids prepared under similar conditions in solution was supported by solution (1)H NMR results, and the unequal stiochiometry of the cationic group from PAH and the anionic group from PSS in the cores of the PEC colloids in solution was identified from solution (1)H NMR results using PEG as external references. On the basis of these, it is suggested that the PEC layers in PEM formed from coating of the adsorbed topmost PAH layers with PSS solution contain excess PSS, and reversely those formed from coating of the adsorbed topmost PSS layers with PAH solution contain excess PAH. Hence a new description of PEM is put forward that the polyelectrolyte multilayers are composed of alternate layers excess either in PSS or in PAH.
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PMID:Finer structures of polyelectrolyte multilayers reflected by solution (1)H NMR. 1881 32

This paper compares the influence of the molecular weight of polylelectrolytes forming polyelectrolyte multilayers (PEM) on wood fibers on adhesion and paper strength. Sheets were made from fibers treated with poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) of molecular mass 70,000 and 240,000, respectively, and of poly(dimethyldiallylammonium chloride) (PDADMAC)/poly(styrene sulfonate) (PSS) of molecular mass 30,000 and 80,000, respectively. The results were compared to what has recently been reported for PEM formation on fibers using a low-molecular-mass combination of PAH and PAA and a high-molecular-mass combination of PDADMAC/PSS. There was a less significant improvement in the case of the low-molecular-mass PDADMAC/PSS and the high-molecular-mass PAH/PAA. The adsorbed amounts of PAH and PDADMAC were also determined, showing a lower adsorbed amount of the low-molecular-mass PAH than of the high-molecular-mass PDADMAC. The amount of low-molecular-mass PDADMAC was similar to that found for high-molecular-mass PDADMAC/PSS. Individual fibers were partly treated and studied, showing a less significant decrease in wettability with low-molecular-mass PDADMAC/PSS than with the high-molecular-mass combination. The effect of the molecular weight on the adhesion was discussed in terms of the structure and wettability of the PEMs.
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PMID:Polyelectrolyte multilayers on wood fibers: influence of molecular weight on layer properties and mechanical properties of papers from treated fibers. 1884 50

Sum-Frequency Vibrational Spectroscopy (SFVS) has been used to investigate the effect of nitrogen-flow drying on the molecular ordering of Layer-by-Layer (LbL) films of poly(allylamine hydrochloride) (PAH) alternated with poly(styrene sulfonate) (PSS). We find that films dried by spontaneous water evaporation are more ordered and homogeneous than films dried by nitrogen flow. The latter are quite inhomogeneous and may have regions with highly disordered polymer conformation. We propose that drying by spontaneous water evaporation reduces the effect of drag by the drying front, while during nitrogen-flow drying the fast evaporation of water "freezes" the disordered conformation of adsorbed polyelectrolyte molecules. These findings are important for many applications of LbL films, since device performance usually depends on film morphology and its molecular structure.
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PMID:Molecular ordering in layer-by-layer polyelectrolyte films studied by sum-frequency vibrational spectroscopy: the effects of drying procedures. 1905 86

In tissue engineering, surface characteristics of a biomaterial are one of most important factors determining the compatibility with the environment. They influence attachment and growth of cells onto the material. In many cases, the surface should to be modified and engineered in the desired direction. The modification of non-adhesive surfaces with polyelectrolyte multilayer films (PMF) was recently depicted as a powerful technique to promote the growth of different cell lines. In this study, we evaluated the possible use of two different PMF as surface modification for the culture of mesenchymal stem cells (MSC). We used two types of PMF which differed by the nature of the initial anchoring layer which was poly(ethylenimine) (PEI) or poly(allylamine hydrochloride) (PAH). This initial polyelectrolytes adsorption was followed by the alternated deposition of poly(sodium 4-styrenesulfonate) (PSS) and (PAH) in order to obtain a PEI-(PSS-PAH)(3) film or a PAH-(PSS-PAH)(3) film. In order to control the behaviour of MSC, the cell viability was evaluated by Alamar Blue assay and the actin cytoskeleton was labelled and visualised in a confocal microscope. The behaviour of cells on the two PMF was compared to cells cultivated on surfaces treated with fibronectin. The results showed that PAH-(PSS-PAH)(3) PMF improve the growth of cells, inducing a higher cell viability compared to PEI-(PSS-PAH)(3) PMF and fibronectin at 2, 3 and 7 days of culture. Moreover, those cells showed a well-organized actin cytoskeleton. In conclusion, PAH-(PSS-PAH)(3) polyelectrolyte multilayer film seems to constitute an excellent material for MSC seeding.
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PMID:Polyelectrolyte multilayer films: effect of the initial anchoring layer on the cell growth. 1906 22

Positively charged poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) complexes (noted as PAH-PAA) with a molar excess of PAH were layer-by-layer (LbL) assembled with polyanion poly(sodium 4-styrenesulfonate) (PSS) to produce multilayer films. The film structure and deposition behavior of the PAH-PAA/PSS films were influenced by the structure of PAH-PAA complexes in solution. For the PAH-PAA complexes with a low ratio of PAA to PAH the PAH-PAA complexes have low-level cross-linking and are flexible. The resultant PAH-PAA/PSS films have a thin film thickness and smooth surface and exhibit a nonlinear deposition behavior where the amount of PAH-PAA complexes and PSS deposited in each deposition cycle are larger than in its previous cycle. The PAH-PAA complexes with a high ratio of PAA to PAH have high-level cross-linking and are rigid. The PAH-PAA/PSS films constructed from the rigid PAH-PAA complexes have a large film thickness and rough surface and exhibit a linear deposition behavior. Deposition of the PAH-PAA/PSS films was well characterized by quartz crystal microbalance, atomic force microscopy, and scanning electron microscopy. The thermally cross-linked PAH-PAA/PSS films can be released from substrate to form stable free-standing films by an ion-triggered exfoliation method. Meanwhile, positively charged PAH-PAA complexes can be LbL assembled with negatively charged PAH-PAA complexes with a molar excess of PAA to produce multilayer films. Use of polyelectrolyte-polyelectrolyte complexes as building blocks for LbL fabrication provides a facile way to tailor the structures of the resultant films by simply changing the structure of the complexes in solution.
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PMID:Layer-by-layer deposition of polyelectrolyte-polyelectrolyte complexes for multilayer film fabrication. 1910 38

Quartz crystal microbalance and cyclic voltammetry are used to investigate the influence of the supporting salt of polyelectrolyte solutions on the buildup and the structure of PSS/PAH polyelectrolyte multilayers (PSS: poly(4-styrene sulfonate); PAH: poly(allylamine hydrochloride)). This film constitutes a model polyelectrolyte multilayer system. The supporting electrolytes were sodium salts where the nature of the anion was changed by following the Hofmeister series from cosmotropic to chaotropic anions (F-, Cl-, NO3-, ClO4-). For all the investigated anions, the film thickness increases linearly with the number of deposition steps.Wefind that chaotropic anions lead to larger thickness increments per bilayer during the film buildup than cosmotropic ones, confirming results found on PSS/PDADMA multilayers (PDADMA:poly(diallyldimethylammonium)). Films constituted by more than nine PSS/PAH bilayers are still permeable to hexacyanoferrate(II) ions, Fe(CN)(6)4-, whatever the nature of the supporting salt anion. On the other hand, these films are impermeable to ruthenium(II) hexamine ions, Ru(NH3)(6)2+, after the third PAH layer in the presence of NaF, NaCl, or NaNO3. These results are explained by the presence of an excess of positive charges in the film, which leads to a positive Donnan potential. We find that this potential is more positive when more chaotropic anions are used during the film buildup. We also find that a film constructed in the presence of chaotropic anions swells and becomes more permeable to Fe(CN)(6)4- ions when the film is brought into contact with a solution containing more cosmotropic anions. All our experimental findings can be explained by a strong interaction between chaotropic anions with the NH3+groups of PAH that is equivalent, as far as the multilayer buildup and electrochemical response is concerned, to a deprotonation of PAH as it is observed when the film is constructed at a higher pH. We thus arrive to a coherent explanation of the effect of the nature of the anions of the supporting electrolyte on the polyelectrolyte multilayer. We also find that great care must be taken when investigating polyelectrolyte multilayer films by electrochemical probing because electrochemical reactions involving the probes can appreciably modify the multilayer structure.
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PMID:Effect of the supporting electrolyte anion on the thickness of PSS/PAH multilayer films and on their permeability to an electroactive probe. 1912 5


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