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PubMed2002

Membranes for biohybrid liver support systems--investigations on hepatocyte attachment, morphology and growth.

The biological properties of four different membranes were studied regarding their possible application in biohybrid liver support systems. Two of them, one made of polyetherimide (PEI), and a second based on polyacrylonitrile-N-vinylpyrollidone co-polymer (P(AN-NVP)), were recently developed in our lab and studied for the first time. Together with pure polyacrylonitrile (PAN) membranes, the three preparations were characterised as ultra-filtration membranes. Their ability to support cell attachment, morphology, proliferation and function of human hepatoblastoma C3A cells was studied. The role of surface morphology for the interaction with hepatocytes was highlighted using a commercial, moderately wettable polyvinylidendifluoride (PVDF) membrane with micro-filtration properties. Comparative investigations showed strongest interaction of C3A cells with PAN membranes, as the focal adhesion contacts were more expressed and cell growth was also high. However, the functional activity in terms of albumin synthesis was reduced. Very similar results were obtained with the most hydrophobic PEI membrane. In contrast, the most hydrophilic membrane P(AN-NVP) was found to provoke stronger homotypic adhesion (E-cadherin expression) of C3A cells and less substratum attachment (focal adhesions), but enhanced albumin secretion. However, proliferation of C3A cells was lowered. Micro-porous PVDF membrane showed very good initial attachment, but the resulting cell material and cell-cell interaction were relatively poor developed. Among four membranes tested, PEI seems to be the most attractive membrane for biohybrid liver devices, as it provides good surface properties for hepatocytes interaction, but in addition it is highly thermostable, which would permit steam sterilisation. No simple relationship, however, between the wettability of the membranes and their ability to support hepatocyte adhesion and function was found in this study.

Acrylic Resins↗
PubMed2003

Characterization of piroxicam crystal modifications.

Piroxicam polymorphism was extensively studied in the past. The objective of the present work was to evaluate polymorphism of piroxicam once again and to characterize the obtained crystal forms. Three polymorphic forms and one monohydrate form were obtained by crystallization from saturated solutions in various solvents. Polarity of solvents and crystallization rate defined by temperature of crystallization were found to be critical parameters in determining the polymorphic form. A new polymorphic form designated as form III was obtained by forced crystallization using dry ice. Only form I with the highest melting point was found to be stable under mechanical and thermal stress. Differences in IR spectra were attributed mainly to the differences in number and positions of H-bonds in the piroxicam crystal forms. Slow crystallization of piroxicam from absolute ethanol solution resulted in a mixture of form II and monohydrate. Crystal structure analysis proved that form II represents form alpha(2) already proposed in the literature. Differences in dissolution rates among crystal forms of piroxicam were attributed to differences in their wettability, where highest wettability was obtained for monohydrate and the lowest for form III.

Crystallization↗
PubMed2005

Surface chemical and mechanical properties of plasma-polymerized N-isopropylacrylamide.

Surface-immobilized poly(N-isopropyl acrylamide) (pNIPAM) is currently used for a wide variety of biosensor and biomaterial applications. A thorough characterization of the surface properties of pNIPAM thin films will benefit those applications. In this work, we present analysis of a plasma-polymerized NIPAM (ppNIPAM) coating by multiple surface analytical techniques, including time-of-flight secondary-ion mass spectrometry (ToF-SIMS), contact angle measurement, atomic force microscopy (AFM), and sum frequency generation (SFG) vibrational spectroscopy. ToF-SIMS data show that the plasma-deposited NIPAM polymer on the substrate is cross-linked with a good retention of the monomer integrity. Contact angle results confirm the thermoresponsive nature of the film as observed by a change of surface wettability as a function of temperature. Topographic and force-distance curve measurements by AFM further demonstrate that the grafted film shrinks or swells depending on the temperature of the aqueous environment. A clear transition of the elastic modulus is observed at 31-32 degrees C. The change of the surface wettability and mechanical properties vs temperature are attributed to different conformations taken by the polymer, which is reflected on the outmost surface as distinct side chain groups orienting outward at different temperatures as measured by SFG. The results suggest that a ppNIPAM thin film on a substrate experiences similar mechanical and chemical changes to pNIPAM bulk polymers in solution. The SFG result provides evidence supporting the current theory of the lower critical solution temperature (LCST) behavior of pNIPAM.

Acrylic Resins↗
PubMed2004

Cell interactions with laser-modified polymer surfaces.

The performance of a polymeric biomaterial depends on the bulk and surface properties. Often, however, the suitability of the surface properties is compromised in favour of the bulk properties. Altering the surface properties of these materials will have a profound effect on how cells and proteins interact with them. Here, we have used an excimer laser to modify the surface wettability of nylon 12. The surface treatment is rapid, cost-effective and can cause reproducible changes in the surface structure of the polymers. Polymers were treated with short wavelength ( < 200 nm) UV light. These wavelengths have sufficient photon energy (6.4eV) to cause bond scission at the material surface. This results in a surface reorganisation with incorporation of oxygen. Surface wettability changes were confirmed using contact angle measurements. Cell interactions with the surfaces were examined using 3T3 fibroblast and HUVEC cells. Cells morphology was examined using a confocal laser scanning microscope (CLSM). Cell activity and cell number on the treated nylon were assessed using biochemical assays for up to seven days. Both fibroblasts and endothelial cells initially proliferated better on treated compared with untreated samples. However, over seven days activity decreased for both cell types on the control samples and endothelial cell activity and cell number also decreased on the treated polymer.

3T3 Cells↗
PubMed2004

Biocompatible Nb2O5 thin films prepared by means of the sol-gel process.

Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability.

3T3 Cells↗
PubMed1995

Non-steroidal anti-inflammatory drugs (NSAIDs) associate with zwitterionic phospholipids: insight into the mechanism and reversal of NSAID-induced gastrointestinal injury.

The molecular basis of the injurious actions of non-steroidal anti-inflammatory drugs (NSAIDs) on the gastrointestinal (GI) tract is only partly understood. In this study we have obtained evidence, employing both in vitro and in vivo systems, that five NSAIDs have the ability to form a chemical association with zwitterionic phospholipids. Since this same class of phospholipids line the luminal aspects of the mucus gel layer to provide it with non-wettable properties, this intermolecular association may be the mechanism by which NSAIDs attenuate the hydrophobic barrier properties of the upper GI tract. Preassociating a number of NSAIDs with exogenous zwitterionic phospholipids prevented this increase in surface wettability of the mucus gel layer and protected rats against the injurious GI side-effects of these drugs, while enhancing their lipid permeability, antipyretic and anti-inflammatory activity.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Rhizobacteria microencapsulation: properties of microparticles obtained by spray-drying.

Rhizobacteria Pseudomonas fluorescens-putida were microencapsulated in Eudragit by spray-drying. These microparticles are subsequently included in seed coating or pelleting material. The survival of the bacterial cell in microparticles were studied under different levels of relative humidity (RH): 0, 33, 55 and 100%. The protective effects of silica, present in certain formulations, were demonstrated at the relative humidities of 33 and 55%. The release of the encapsulated bacteria was also studied over time. The release was fast, the bacteria being observed at 15 min immersion of the Eudragit microparticles in an aqueous-buffer medium at 20 degrees C. This result, related to the physicochemical character of the coating polymer, showed that water was the triggering element for the release of rhizobacteria. Compatibility studies between two film-forming agents used for seed coatings and the encapsulated bacteria, as well as wettability measures of tableted microparticles, were carried out. The bacterial survival was good with the seed coating agent, Sepiret 1039G, and the wettability measurements of agglomerated microparticles were in accord with the rapid release of the microencapsulated bacteria. The application of microparticles containing rhizobacteria on seeds can now be considered for preliminary trials.

Acrylic Resins↗
PubMed2006

Recent developments in superhydrophobic surfaces and their relevance to marine fouling: a review.

In this review, a brief synopsis of superhydrophobicity (i.e. extreme non-wettability) and its implications on marine fouling are presented. A short overview of wettability and recent experimental developments aimed at fabricating superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e. substratum texture) are reviewed. The formation of responsive/"smart" surfaces, which adjust their physico-chemical properties to variations in some outside physical stimulus, including light, temperature, electric field, or solvent, is also described. Finally, implications of tailoring the surface chemistry, texture, and responsiveness of surfaces on the design of effective marine fouling coatings are considered and discussed.

Animals↗
PubMed2005

The influence of surface energy on the wetting behaviour of the spore adhesive of the marine alga Ulva linza (synonym Enteromorpha linza).

The environmental scanning electron microscope has been used to image the adhesive pads secreted by zoospores of the marine alga Ulva linza as they settle on a range of self-assembled and grafted monolayers of different wettability, under natural, hydrated conditions. Results reveal that the diameter of the adhesive pad is strongly influenced by surface wettability, the adhesive spreading more (i.e. wetting the surface better) on the more hydrophilic surfaces. This is in direct contrast to previous observations on the spreading of marine bioadhesives and is in apparent contradiction to the predictions of the Young-Dupre equation for three-phase systems. In this paper, we attempt an explanation based upon thermodynamic analysis of the wetting properties of hydrophilic proteins.

Adhesiveness↗
PubMed2005

Three-dimensional mixed-wet random pore-scale network modeling of two- and three-phase flow in porous media. I. Model description.

We present a three-dimensional network model to simulate two- and three-phase capillary dominated processes at the pore level. The displacement mechanisms incorporated in the model are based on the physics of multiphase flow observed in micromodel experiments. All the important features of immiscible fluid flow at the pore scale, such as wetting layers, spreading layers of the intermediate-wet phase, hysteresis, and wettability alteration are implemented in the model. Wettability alteration allows any values for the advancing and receding oil-water, gas-water, and gas-oil contact angles to be assigned. Multiple phases can be present in each pore or throat (element), in wetting and spreading layers, as well as occupying the center of the pore space. In all, some 30 different generic fluid configurations for two- and three-phase flow are analyzed. Double displacement and layer formation are implemented as well as direct two-phase displacement and layer collapse events. Every element has a circular, square, or triangular cross section. A random network that represents the pore space in Berea sandstone is used in this study. The model computes relative permeabilities, saturation paths, and capillary pressures for any displacement sequence. A methodology to track a given three-phase saturation path is presented that enables us to compare predicted and measured relative permeabilities on a point-by-point basis. A robust displacement-based clustering algorithm is also presented.

Absorption↗
PubMed2007

Evaluation of the surface free energy on root canal dentine walls treated with chelating agents and NaOCl.

AIM: To evaluate ex vivo the effects of combined and single use of EDTA, RC-Prep and NaOCl on the surface free energy of canal wall dentine using the captive bubble technique. METHODOLOGY: Eighteen extracted human pre-molar teeth were sectioned at the crown and the apical third, the remaining mid-root portion were bisected longitudinally. Thereafter, the root halves were embedded in resin blocks that exposed the dentine surface of the canal wall. The specimens were randomly assigned to six experimental groups (n = 6) after polishing. The root dentine surfaces of the first two groups were treated with 17% EDTA or RC-Prep followed by 2.5% NaOCl irrigation. Groups 3, 4 and 5 were treated with either 17% EDTA, RC-Prep or 2.5% NaOCl alone. Control specimens were irrigated with saline solution. The surface free energies of experimental groups were calculated by measuring air and octane contact angles on the canal wall dentine. Statistical analysis was performed using the Mann-Whitney U and Bonferroni post-tests at P = 0.05. RESULTS: Compared with the control group; combined and single use of EDTA, RC-Prep and NaOCl irrigation significantly decreased the surface free energy of canal wall dentine surfaces (P < 0.05). Among all groups tested, the use of NaOCl as a final flush following RC-Prep treatment yielded increased wettability. Nevertheless, this value remained lower than that of the control group. CONCLUSION: Use of chelating agents alone or in combination with NaOCl decreased the wettability of root canal wall dentine.

Bicuspid↗
PubMed1994

Effect of immersion disinfection on properties of impression materials.

PURPOSE: Dimensional change and wettability were determined for three addition silicones and a polyether impression material after disinfection by immersion for two 30-minute cycles in 2% acid-potentiated glutaraldehyde. MATERIALS AND METHODS: Contact angles of water on disks were measured on a goniometer. Dimensional change was determined by change in distance between two reference lines. Contact angle (degree) and dimensional change (percent) of five samples were measured after 0-, 30-, 60-, and 1,440-minute intervals of storage in air and disinfectant. RESULTS: The contact angle in air increased for two addition silicones and remained constant for the remaining materials. In disinfectant, the contact angle increased for all four materials, with the contact angle of the polyether increasing the least. In air, dimensional change decreased significantly for an addition silicone and a polyether. In disinfectant, the dimensional changes of the addition silicones were not significant, but the polyether increased in dimension after 1,440 minutes. CONCLUSIONS: Two 30-minute cycles of disinfection in 2% acid-potentiated glutaraldehyde reduced wettability, but had little effect on the dimensional change of the addition silicones and polyethers tested.

Analysis of Variance↗
PubMed2001

Adhesion and proliferation of rat vascular smooth muscle cells (VSMC) on polyethylene implanted with O+ and C+ ions.

Polyethylene was implanted with 30-keV oxygen (PE/O+) or 23-keV carbon ions (PE/C+) at 10(13) to 5 x 10(15) ions cm(-2) doses in order to improve the adhesion of vascular smooth muscle cell (VSMC) to the polymer surface in vitro because of its oxidation and carbon-enrichment. The concentration of -CO- groups in the PE/O+ and PE/C+ samples increased only up to doses of 3 x 10(14) and 10(15) ions cm(-2), respectively, and then declined. At the same time, the concentration of these groups, measured at a dose of 3 x 10(14) ions cm(-2), was higher in PE/O+ than in PE/C+ samples. Similarly, the number of initially-adhering rat VSMC (24 h after seeding) increased only up to a dose of 3 x 10(13) and 10(15) ions cm(-2) on PE/O+ and PE/C+ samples, respectively. In addition, between doses of 10(13) and 10(14) ions cm(-2), this number was about two to three times higher on PE/O+ samples. On the other hand, the surface wettability increased proportionally to the implanted ion dose, especially above a dose of 10(14) ions cm(-2). Thus, the number of initially-adhered cells appeared to be positively correlated with the amount of the oxygen group present at the polymer surface rather than with the surface wettability. The higher cell adhesion was accompanied by adsorption of fluorescent dye-conjugated collagen IV in larger amounts. The highest numbers of initially-adhered cells were usually associated with the lowest rates of subsequent proliferation (measured by the doubling time, BrdU labelling and M

Animals↗
PubMedDate not supplied

Potential use of cutinase in enzymatic scouring of cotton fiber cuticle.

The present study characterized the ability of a bacterial cutinase to improve the wettability of raw cotton fabrics by specific hydrolysis of the cutin structure of the cuticle. The effect of cutinase was studied alone and in coreaction with pectin lyase. The changes in both the fabric and the reaction fluid were measured and compared to enzymatic hydrolysis with polygalacturonase, and to chemical hydrolysis with boiling NaOH. Water absorbancy, specific staining, fabric weight loss, and evaporative light-scattering reverse-phase high-performance liquid chromatography analysis of chloroform extract of the reaction fluid were measured to assess the enzymatic hydrolysis of the cuticle waxy layer. The pattern and extent of hydrolysis of the major cuticle constituents depended on the enzyme type and titers employed and paralleled the degree of wettability obtained. The combination of cutinase and pectin lyase resulted in a synergistic effect. The use of detergents improved enzymatic scouring. The major products released to the reaction medium by the cutinase treatment were identified by gas chromatography/mass spectrometry analysis as C:16 and C:18 saturated fatty acid chains.

Aspergillus niger↗
PubMed2001

Influence of self-etching primer on the resin adhesion to enamel and dentin.

PURPOSE: To evaluate the shear bond strength of resin-based composite to dentin and enamel using three adhesive systems, two of them containing self-etchant primers. Wettability (contact angle measurements) of the primers of these three adhesive systems was also evaluated on superficial and deep dentin. MATERIAL AND METHODS: Contact angle measurements were performed on 30 caries-free extracted human third molars; specimens were sectioned parallel to the occlusal surface to expose superficial and deep dentin. Dentin was ground flat (600-grit SiC) under water to provide uniform surfaces. Contact angle measurements were performed to assess wettability using the Axisymmetric Drop Shape Analysis technique. In order to test the enamel bond strength, 30 extracted bovine incisors were embedded in acrylic resin and ground flat to 800-grit. The adhesives and composite resins were applied following the manufacturers' instructions. All the specimens were stored in water for 24 hrs at 37 degrees C and thermocycled (500x). Shear bond strengths were determined using a universal testing machine and the Watanabe device. For dentin bond strength testing, superficial and deep dentin was exposed in 60 third molars, by sectioning the occlusal surface immediately under the enamel-dentin junction or close to the pulp chamber. After grinding (500 grit SiC), the dentin surfaces were assigned to three groups: (1) Clearfil SE Bond (CSEB)/Clearfil AP-X resin composite. (2) Etch & Prime (E&P)/Degufill mineral resin composite. (3) Scotchbond Multi-Purpose Plus (SBMP)/Z100 resin composite. RESULTS: One-way ANOVA and Student-Newman-Keuls multiple comparisons tests showed that no differences were found between contact angles on superficial and deep dentin. CSEB and E&P, without significant differences between them, had greater mean contact angle than SBMP. On enamel, Etch & Prime resulted in the lowest bond strength, but no significant differences existed with Scotchbond Multi-Purpose were found. On dentin, Clearfil SE Bond resulted in the significantly highest bond strength; no significant differences exist between Etch & Prime and Scotchbond Multi-Purpose.

Acid Etching, Dental↗
PubMedDate not supplied

Influence of eugenol contamination on the wetting of ground and etched dentin.

Forty third molars were sectioned parallel to the occlusal surface in order to expose superficial and deep dentin. Exposed surfaces were ground flat with 500-grit sandpaper. Contact angle measurements were performed to assess wettability using the ADSA-CD technique. Specimens were divided into two groups. Group 1 was the control group (no contamination). Group 2 served as the test group. Dentin surfaces were covered with a provisional eugenol-containing material (IRM) and were placed into a humidor at 37 degrees C for one week. The provisional material was removed. Wettability measurements of the two groups were made with water on ground dentin, with water and resin on etched dentin. Data were statistically analyzed by ANOVA, Student-Newman-Keuls multiple comparison and Student t-tests. Eugenol contamination did not affect the dentin wetting. Acid etching significantly diminished contact angle values. Dentin wetting was greater on deep dentin than on superficial dentin.

Acid Etching, Dental↗
PubMedDate not supplied

Characterization of treated porcelain surfaces via dynamic contact angle analysis.

Successful porcelain repair requires conditioning of porcelain surfaces. Conditioning is intended to facilitate wetting by repair materials and improve interfacial bonding. The objective of this investigation was to determine the effects of selected surface treatments upon the wettability of a representative feldspathic porcelain. Dynamic contact angle analysis and scanning electron microscopy were used to characterize the effects of such treatments. Standardized porcelain specimens were subjected to the following five treatment regimens: (1) control (no treatment); (2) airborne particle abrasion using 50 microns aluminum oxide; (3) etching with ammonium bifluoride gel; (4) etching with acidulated phosphate fluoride gel; and (5) etching with hydrofluoric acid gel. Following treatment, specimens were cleansed and dried. Advancing contact angles were quantified using dynamic contact angle analysis. Mean values and 95% confidence intervals were (in degrees): control, 63.8 +/- 2.7; ammonium bifluoride, 39.4 +/- 2.0; airborne particle abrading, 29.1 +/- 2.9; acidulated phosphate fluoride, 24.9 +/- 1.7; and hydrofluoric acid, 16.5 +/- 1.2. Significant differences were found between all treatment groups (P = .05). Subsequent scanning electron microscopy examination of treated surfaces indicated lesser contact angles were associated with surfaces displaying deeper and wider grooves. Apparently, the resultant increase in surface area produces increased wettability. It is inferred that an increase in surface area may correspond to enhanced resin-porcelain bonding.

Acidulated Phosphate Fluoride↗