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PubMed1995

Biocompatibility of polysulfone II. Platelet adhesion and cho cell growth.

Experimental results on the platelet adhesion, and CHO cell adhesion and growth onto nonionic surfactant which is composed of a long alkyl chain (n = 12-18) as the hydrophobic part, and a polyethyleneoxide (PEO) segment (n = 10-23) as the hydrophilic part coated and air-plasma treated PSf surfaces are presented in terms of PEOs functionality and surface wettability to improved blood- and cell-compatibility of polysulfone. Platelet adhesion experiments on surface treated PSf films were carried out with platelet enriched plasma (PRP) in the parallel flow chamber in vitro. Number and morphology of adhered platelets were observed by scanning electron microscope. The number of adhered platelets on nonionic surfactant coated surfaces decreased significantly compared to the control. Also, the adhesion of platelets on to PSf substrate decreased with increasing coating concentration of nonionic surfactant. In the dry air-plasma exposed PSf sample, the adhesion of platelets decreased independently of plasma exposure time, and significant diminution of platelet adhesion was observed below about 40 degrees of the contact angle. It is believed that less platelet adhesion is preceded by less protein adsorption due to hydrophobic dehydration interaction. In Chinese hamster ovary (CHO) cell, adhesion and growth cells grew better on the air-plasma treated PSf surfaces. From these results, it can be proposed that surface wettability of PSf is very important for cell adhesion and growth.

Adsorption↗

PubMedDate not supplied

A suggested method for mixing direct filling restorative gallium alloy.

Good wettability is one of the desirable physical properties of mercury-free gallium-based alloys (Gallium Alloy GF). However, wettability, while providing good adhesion to the cavity wall, has the adverse effect of causing stickiness to the inside of the capsule during mixing, and also to the metal hand instruments used for packing. To control this stickiness the alloy mixture was treated with a small amount of alcohol using two different methods. In both groups (alcohol-added and alcohol-treated groups), 5, 10, or 15 microliters of alcohol was added. However, for the alcohol-treated group, the alcohol was shaken from the mixture. In both groups, remarkable improvement was seen in their handling properties, for the alloy mixture did not adhere to the inside of the capsule and was easily taken out as one mass. Compressive strength, tensile strength, and creep were tested in the alcohol-added/-treated groups, and compared with those of a control (conventionally mixed gallium alloy) and a high-copper amalgam (Spherical-D). All tests were done according to ISO 1559 (International Organization for Standardization, 1986), and the results were analyzed using one-way ANOVA (Duncan, P < 0.05). Surface microhardness (KHN) and dimensional change during hardening were evaluated according to ISO 1559 and compared to the control results. In mixing Gallium Alloy GF, an addition of less than 5 microliters of alcohol had the effect of preventing the alloy mixture from sticking to the inside of the capsule and remarkably enhanced the handling properties. This suggested mixing technique did not alter either the mechanical properties tested for this material or the desirable dimensional expansion that occurs during hardening.

Alloys↗

PubMed1997

Characterization and development of RGD-peptide-modified poly(lactic acid-co-lysine) as an interactive, resorbable biomaterial.

The design of biomaterials containing specific ligands on the surface offers the possibility of creating materials that can interact with and potentially control mammalian cell behavior. Biodegradable materials further provide the significant advantage that the polymer will disappear in vivo, obviating long-term negative tissue responses as well as the need for retrieval. In earlier studies we synthesized and characterized arginine-glycine-aspartic acid (RGD) peptide-modified poly(lactic acid-co-lysine) (PLAL). In this study, both bulk properties and surface features have been characterized, with a focus on surface analysis as a means of interpreting observed changes in cell behavior. Bulk peptide attachments were performed using 1,1'-carbonyldiimidazole (CDI). Amino groups were measured using colorimetric assays and X-ray photoelectron spectroscopy (XPS). Peptides were measured by incorporating iodine into the peptide as a distinct elemental marker for use with XPS. Typical samples contained 13 +/- 4 pmol/cm2 of amino groups and 4 +/- 0.2 pmol/ cm2 of peptides, as calculated from XPS measurements of nitrogen and iodine. The wettability and crystallinity of the samples were determined by contact angles and differential scanning calorimetry, respectively. Wettability and crystallinity were not altered by the incorporation of lysine or peptides. After incubating bovine aortic endothelial (BAE) cells for 4 h on surfaces with RGD-containing peptides, the mean spread cell area increased from 77 +/- 2 microns2 to 405 +/- 29 microns2 compared to 116 +/- 11 microns2 on poly(lactic acid), 87 +/- 4 microns2 on PLAL, and 105 +/- 4 microns2 on surfaces with RDG-containing (control) peptides. The significance of this work is that the first synthetic interactive, resorbable biomaterial has been developed, and use of this material to control cell behavior has been demonstrated.

Animals↗

PubMed2000

Host-guest interactions at self-assembled monolayers of cyclodextrins on gold

We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding.

Journal Article↗

PubMed2002

Adhesion behavior of monocytes, macrophages, and foreign body giant cells on poly (N-isopropylacrylamide) temperature-responsive surfaces.

Monocyte and macrophage adhesion and foreign body giant cell (FBGC) formation has been observed on surfaces with a wide range of properties. In this study we have utilized novel, temperature-responsive surfaces (TRS) with dynamic surface properties to investigate inflammatory cell adhesion behavior. With temperature changes, grafted chains of poly-N-isopropylacrylamide pass through their lower critical solution temperature (LCST) and can either extend (hydrate), creating a hydrophilic surface at 20 degrees C, or contract (dehydrate), creating a hydrophobic surface at 37 degrees C. Isolated human monocytes and monocyte-derived macrophages were able to adhere, spread, and form FBGC on the hydrophobic surface. Decreasing the temperature below the lower critical solution temperature induced a change in the surface wettability, creating a hydrophilic surface, that induced a differential detachment of adherent cells that decreased with time, ranging from 98% after 2 h of culture to 30% at day 10. These detached cells remained viable, and were recultured onto TCPS for 3, 7, and 10 days. These novel surfaces allow investigation of the adhesive behavior of adherent inflammatory cells in a temporal manner, and the effects of surface conformation and wettability changes on cell adhesion and detachment.

Cell Adhesion↗

PubMed1993

Effect of a combined gamma irradiation and Parylene plasma treatment on the hydrolytic degradation of synthetic biodegradable sutures.

The aim of this study was to alter the hydrolytic degradation property of synthetic absorbable suture fibers so that their mass loss would occur at a shorter time without significantly compromising their tensile strength loss profile. A two-step treatment concept (gamma-irradiation followed by Parylene plasma deposition) was introduced for achieving this aim. Vicryl and Maxon were used as the model compounds to test this new concept. After the treatment, the in vitro hydrolytic degradation properties of Vicryl and Maxon were evaluated by weight loss, tensile breaking strength, heat of fusion and melting temperature, intrinsic viscosity, surface wettability, and surface morphology. The results suggested that gamma-irradiation at a dosage level between 0.2-2.0 Mrad for Vicryl sutures and about 2.0 Mrad for Maxon sutures were the most effective dosages to accelerate the suture mass loss. The subsequent Parylene plasma deposition treatment statistically significantly improved the retention of tensile strength for both gamma-irradiated Vicryl and Maxon sutures and hence counteracted the undesirable gamma-irradiation induced acceleration of tensile strength loss. However, this second-step Parylene plasma treatment extended the suture mass loss to longer periods. These findings were consistent with the observed surface wettability, surface morphology, intrinsic viscosity, and thermal properties. A thin hydrophobic Parylene skin layer wrapped around a suture was responsible for the slower rate in mass and strength loss. This outer skin layer acted as a barrier to not only water but also degradation fragments.

Biodegradation, Environmental↗

PubMed2003

Protein adsorption on mixtures of hydroxyl- and methyl-terminated alkanethiols self-assembled monolayers.

The effect of surface composition and wettability on the adsorption of human serum albumin (HSA) was studied. Self-assembled monolayers (SAMs) containing mixtures of longer chain methyl- and shorter chain hydroxyl-terminated alkanethiols on gold were used to produce a range of surfaces with different wettabilities and exposed functional groups. Different SAMs were characterized by X-ray photoelectron spectroscopy, water contact angles, and Fourier transform infrared reflection absorption spectroscopy (IRAS). HSA adsorption onto the different SAMs was evaluated by contact angle measurements (wetting tension determinations), radiolabeling of proteins, and IRAS. Concerning HSA adsorption, all the techniques demonstrated higher HSA adsorption on more hydrophobic surfaces. The wetting tension measurements and IRAS suggested a gradual decrease of the HSA adsorption with increases of surface hydrophilicity. Radiolabeled albumin measurements also demonstrated a significant decrease of HSA adsorption on the pure hydroxyl-terminated SAMs. However, no significant differences were detected between mixed and pure methyl-terminated SAMs. Studies of HSA exchangeability with human fibrinogen have suggested that an ideal percentage of hydroxyl groups on the surface may increase albumin affinity without fibrinogen adsorption.

Adsorption↗

PubMed2003

Gas plasma etching of PEO/PBT segmented block copolymer films.

A series of poly(ethylene oxide)/poly(butylene terephthalate) (PEO/PBT) segmented block copolymer films was treated with a radio-frequency carbon dioxide (CO(2)) or with argon (Ar) plasma. The effects of (preferential) etching on surface structure, topography, chemistry, and wettability were studied by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. In all cases, a granular-type nanostructure was formed after prolonged CO(2) plasma etching. Ar plasma etching generally did not lead to significant changes in surface structure. Regarding surface chemistry, CO(2) plasma treatment caused surface oxidation and oxidative degradation of the films while Ar plasma etching resulted mainly in the preferential removal of PEO blocks. The wettability of all films significantly increased after plasma treatment because of the creation of polar functional groups at the surface. Preliminary goat bone-marrow cell compatibility experiments have shown that all plasma-treated PEO/PBT films induced a greatly enhanced cell adhesion and/or growth compared to untreated biomaterials. This improvement was attributed to changes in surface chemistry during plasma etching rather than to changes in surface structure. These results show that plasma-treated PEO/PBT copolymers have a high potential as scaffolds for bone tissue regeneration.

Animals↗

PubMed2004

Systematic variation in osteoblast adhesion and phenotype with substratum surface characteristics.

Time-varying interactions of human fetal osteoblastic cells (hFOB 1.19) with materials of diverse chemical composition and surface energy, including biodegradable lactide/glycolide-based polymers, were assessed using a combination of assays sensitive to different phases of cell-substratum compatibility. Short-term (minutes to hours) cell-attachment-rate assays were used to measure the earliest stages of cell-surface interactions leading to adhesion. Proliferation-rate assays quantifying viability of attached cells were applied as a measure of medium-term (hours to days) cytocompatibility. Both attachment- and proliferation-rate assays were found to strongly correlate with material surface energy, with the exception of a reproducible and significant adhesion preference for fully water-wettable quartz over glass. No such adhesion/proliferation preference was observed for hydrophobized counterparts, and attachment to water-wettable glass was significantly less than that to control tissue culture polystyrene. These results suggest that the amorphous SiO(x) surface was inhibitory to hFOB 1.19 growth whereas putatively crystalline quartz stimulated bioadhesion. Alkaline phosphatase activity was evaluated as a marker for long-term (days) differentiation of hFOB 1.19 cells and did not strongly correlate with surface energy or, in the case of biodegradable polymers, chemical composition.

Alkaline Phosphatase↗

PubMed2004

On the role of CO2 laser treatment in the human serum albumin and human plasma fibronectin adsorption on zirconia (MGO-PSZ) bioceramic surface.

The nature of the surface strongly influences the composition and recognizability of the adsorbed protein layer, which in turn affects the subsequent cellular interactions. Thus, to understand the biological response to a material, especially in vitro, one must fully understand the nature of the adsorbed protein film that forms on the material. This study investigates the fundamental interactions between the human serum albumin (no-cell adhesive) and human plasma fibronectin and bioinert ceramic following CO(2) laser treatment. The analysis of the albumin and fibronectin adsorption was conducted on the untreated and CO(2) laser-modified magnesia partially stabilized zirconia (MgO-PSZ) bioceramic using an ellipsometry. It was found that the adsorptions of albumin and fibronectin were influenced by the surface properties. The albumin adsorption was affected by the surface roughness and wettability characteristics of the MgO-PSZ and decreased with these properties, while the fibronectin adsorption was increased with wettability characteristics and predominantly governed by this property. Moreover, the considerable change in the polar component of surface energy, gamma(sv) (p), and its effect on protein adsorption implied that the albumin and fibronectin adsorption on the MgO-PSZ surfaces was probably due to the polar and chemical interactions. The value of this work is to provide a novel technique and useful information for manipulating protein adsorption and thereof cellular interactions.

Biocompatible Materials↗

PubMed2007

Polydimethylsiloxane as a substrate for retinal pigment epithelial cell growth.

Retinal pigment epithelial (RPE) cell transplantation represents potential treatment for age-related macular degeneration (AMD). Because delivery of isolated cells can cause serious complications, it is necessary to develop a suitable transplant membrane that could support an intact functioning RPE monolayer. Polydimethylsiloxane (PDMS) possesses the physical properties required for a transplanting device and is widely used clinically. We have investigated the use of PDMS as a potential surface for the growth of healthy RPE monolayers. PDMS discs were surface modified by air and ammonia gas plasma treatments. Dynamic contact angles were measured to determine the changes in wettability. Human ARPE-19 cells were seeded onto untreated and treated samples. Cell number, morphology and monolayer formation, cytotoxicity, and phagocytosis of photoreceptor outer segments (POS) were assessed at set time-points. Air plasma treatment increased the wettability of PDMS. This significantly enhanced cell growth, reaching confluence by day 7. Immunofluorescence revealed well-defined actin staining, monolayer formation, and high cell viability on air plasma treated and untreated surfaces, and to a lesser extent, on ammonia plasma treated. Furthermore, RPE monolayers were able to demonstrate phagocytosis of POS in a time-dependent manner similar to control. PDMS can support an intact functional monolayer of healthy differentiated RPE cells.

Cell Line↗

PubMed2004

In vitro nimesulide absorption from different formulations.

In light of improving the bioavailability of poorly water-soluble drugs, this work focused on the comparison among different nimesulide formulations resorting to in vitro absorption experiments through everted rat intestine. The performance of a nimesulide ethanol-triacetin solution, an activated system made up by cogrinding nimesulide/polyvinylpyrrolidone and simple solid nimesulide were compared with that of a reference nimesulide solution. Although ethanol-triacetin solution showed a better performance than the solid nimesulide because wettability problems connected with nimesulide were completely zeroed, the activated system showed a better performance than the reference solution one. This was due to the fact that the activated system allowed to overcome both the wettability and solubility problems connected with nimesulide. Moreover, as proved by intestinal pictures taken before and after permeation experiments, we observed the adhesion of polymeric particles to intestinal villi, this giving origin to a thin layer, surrounding the intestine, characterized by a nimesulide concentration higher than that in the release environment bulk. A proper mathematical model, based on Fick's second law, was developed to model drug absorption in the case of solution and activated system. In this manner, we could calculate nimesulide permeability through the intestinal wall, and we could better define the nature of the above-mentioned thin layer surrounding the intestine. Finally, the mathematical model was used to verify the theoretical correctness of the widely employed technique consisting in data correction for dilution when sample withdrawal and replacement were needed to measure drug concentration in the receiver environment.

Absorption↗

PubMed2002

Susceptibility of house flies (Diptera: Muscidae) exposed to commercial insecticides on painted and unpainted plywood panels.

House flies were collected from dairies in New York state and the levels of resistance to commercially available insecticide formulations were measured on painted and unpainted plywood panels. Dimethoate was ineffective on all surfaces. The wettable powder permethrin formulation was more toxic than the emulsifiable concentrate formulation. The wettable powder cyfluthrin formulation was also more toxic than the recently developed liquid formulation. In general, the best house fly control was obtained on flat latex painted plywood panels and the poorest control on gloss latex painted panels. It is highly unlikely that producers obtain adequate control with dimethoate and permethrin.

Animals↗

PubMed1996

Contact Angle Studies of Ethyl Xanthate Coated Galena Particles

The wettability of ethyl xanthate coated galena particles has been determined from measurements of the equilibrium capillary pressure across a packed bed. Both the advancing liquid powder contact angle, thetap, and the specific wettable surface area, Awet, of galena particles have been obtained. The influence of particle size and ethyl xanthate surface coverage on the powder contact angle have been investigated and compared with floatability. Ethyl xanthate at a surface coverage of less than ten percent of an equivalent monolayer significantly increases both thetap and particle floatability.

Journal Article↗

PubMed1997

Chemical Interactions of Ultraviolet Light with Wool Fiber Surfaces

The surface compositions, chemistry, and wettability of wool fiber fabrics in both native and UV-exposed states have been investigated. X-ray photoelectron spectroscopy shows surface oxygen levels of 10-12 at.% for native wool, which increase to as much as 27.5 at.% on UV exposure. Investigation of C1s and S2p photoelectron line energies shows this increase to be due largely to oxidative cleavage of native disulfide bonds to form sulfonic acid groups together with some formation of COOH/COOR on the wool fiber surfaces. A quantitative relationship is demonstrated between surface chemical states and water wettability. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed1999

Surface Modification of Conventional Polymers by Depositing Plasma Polymers of Trimethylsilane and of Trimethylsilane + O2.

The dynamic wetting properties of TMS (trimethylsilane) and TMS + O2 plasma-deposited films on ten low energy conventional polymers were investigated using the Wilhelmy balance method. Plasma deposition resulted in wetting properties that were independent of the underlying polymer substrate for the majority of polymers studied. TMS plasma modification resulted in virtually the same degree of hydrophobicity with an average cosine of the dynamic advancing contact angle from the first immersion, cos θD,a,1 = -0.381 (θD,a,1 = 112 +/- 3.6), for eight of the ten polymers. PTFE and UHMWPE were slightly more hydrophobic after TMS plasma treatment with an average cos θD,a,1 = -0.785 (θD,a,1 = 141 +/- 4.2). TMS + O2 plasma modification resulted in high wettability of all polymers with an average cos θD,a,1 = 0.654 (θD,a,1 = 49.2 +/- 11.7). Dynamic hysteresis, mainly a result of the change in meniscus shape during immersion and emersion, and intrinsic hysteresis, due to the extent of surface configuration change, were both found to vary according to the size of the polymer plate. In general, dynamic hysteresis can be quite large for more hydrophobic TMS treated polymers and considerably smaller for highly hydrophilic TMS + O2 treated polymers. The extent of intrinsic hysteresis of only TMS treated polymers was found to be independent of the underlying polymers within the time-scale of wetting. TMS + O2 plasma treatment resulted in wide variations in intrinsic hysteresis probably due to substrate specific etching of oxygen plasma species. The wettability of the untreated and TMS and TMS + O2 treated polymers, indicated by the static "advancing" contact angles from the sessile droplet method and dynamic "advancing" and "receding" contact angles from the Wilhelmy balance method, were found to conform well to the correlation, cos θS = (cos θD,a,1 + cos θD,r,1)/2. Copyright 1999 Academic Press.

Journal Article↗

PubMed2000

Thermodynamic Approach to the Wetting of Solids by Surface-Active Agents: A Supplementary Approach to the Gibbs Formalism.

The adsorption of a solute on a solid can be followed by contact angle measurements of a drop of the solution on the solid. The Gibbs isotherm model can be used for quantitative interpretation of wettability variations. Its use in linking the wettability to the adsorption isotherm involves assimilating the Gibbs' planes to the surfaces themselves. Within this framework, these interpretations lead to the conclusion that adsorption of surface-active agents is greater on solid-vapor interfaces than on solid-liquid interfaces, for hydrophilic solids. This is not the only approach. Thermodynamics allows other formalisms, the conclusions of which can be completely different. We present a thermodynamic approach which explicitly reveals relationships between surface tensions and contents of surfaces, without referring to the Gibbs' plane. This permits us to explain the behavior of a drop of surfactant solution put on hydrophilic or hydrophobic solids with conclusions different from those reached using the Gibbs approach. We show that all these thermodynamic approaches are linked; they do not dismiss one another but give different views of the same phenomenon. Copyright 2000 Academic Press.

Journal Article↗

PubMed1993

Phospholipase activity of Helicobacter pylori and its inhibition by bismuth salts. Biochemical and biophysical studies.

In this study we measured phospholipase A (PLA) and C (PLC) activity of media filtrates and French Press lysates of the gastritis-inducing bacteria Helicobacter pylori. We report here that both H. pylori lysates and filtrates contain PLA1, PLA2, and C enzymes, which readily hydrolyze a radiolabeled dipalmitoylphosphatidylcholine (DPPC) and phosphorylcholine substrates, respectively. The specific activity of both PLA and C enzymes were greatest in the 6.5-7.0 and 8.4-8.8 pH ranges, respectively. Colloidal bismuth subcitrate (CBS) induced a dose-dependent inhibition of PLA2 and C activity of both H. pylori lysates and filtrates. This inhibitory effect of CBS on PLA2 was antagonized in a dose-dependent fashion by the addition of CaCl2 to the incubation mixture, suggesting that calcium and bismuth may be competing for the same site on the enzyme. In contrast, the ability of bismuth salts to inhibit PLC activity of H. pylori lysates was not antagonized by CaCl2. Employing a biophysical assay system for surface wettability, it was determined that H. pylori lysates had the capacity to remove a synthetic phospholipid monolayer off a glass in a dose-dependent fashion. This ability of the bacterial lysates to catalyze the transformation of a hydrophobic surface to a wettable state was significantly attenuated in the presence of bismuth salts. Our experimental results are, therefore, consistent with the possibility that H. pylori colonization compromises the stomach's barrier to acid by eroding a phospholipid lining, possibly a monolayer, on the surface of the gastric mucus gel and that this process is blocked in response to bismuth therapy.

Anti-Bacterial Agents↗