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PubMed2006

Human microvascular endothelial cellular interaction with atomic N-doped DLC compared with Si-doped DLC thin films.

This article reports results of endothelial cell interaction with atom beam source N-doped a-C:H (diamond-like carbon, DLC) as it compares with that of Si-doped DLC thin films. The RF plasma source exhibits up to 40% N-dissociation and N-atomic fluxes of approximately 0.85 x 10(18) atoms/s, which ensures better atomic nitrogen incorporation. Two different types of nitrogen species (with and without the use of sweep plates to remove charged ions) were employed for nitrogen doping. The number of attached endothelial cells is highest on Si-DLC, followed by the N-DLC (where the sweep plates were used to remove ions), the N-DLC (without the use of sweep plates), undoped DLC, and finally the uncoated sample. The contact angle values for these films suggest that water contact angle is higher in the atomic nitrogen neutral films and Si-DLC films compared to the ionized-nitrogen specie doped films and undoped DLC thin films, suggesting that the more hydrophobic films, semiconducting films, and film with relieved stress have better interaction with human microvascular endothelial cells. It seems evident that N-doping increases the Raman I(D)/I(G) ratios, whereas N-neutral doping decreases it slightly and Si-doping decreases it even further. In this study, lower Raman I(D)/I(G) ratios are associated with increased sp(3)/sp(2) ratio, an increased H concentration, photoluminescence intensity, and a higher endothelial cellular adhesion. These investigations could be relevant to biocompatibility assessment of nanostructured biomaterials and tissue engineering.

Cell Adhesion↗
PubMed2004

Drying of poloxamer hydrogel films.

The drying of hydrogel films formed by Poloxamer 407 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) amphiphilic block copolymer was investigated at various air relative humidity (RH) conditions ranging from 11 to 97%. Initially, the amount of water lost increased linearly with the drying time. After this linear region (stage I), a nonlinear behavior was observed (stage II). The drying rate increased with decreasing RH, thus greatly shortening the drying time. A decrease of the film thickness also shortened the drying time; however, the drying mechanism did not change. Three models for one-dimensional water diffusion were used to fit the experimental results at different RH conditions and film thicknesses. Model 1 assumes semi-infinite medium and constant diffusion coefficient, and fits very well the data in stage I of the drying process. The fitted water diffusion coefficient (D) is 5 x 10(-10) m(2)/s, whereas the effects of the RH are captured by a proportionality constant (alpha) that appears in the boundary condition. Model 2 considers a finite (constant) film thickness and captures the experimental observations over the whole drying period for the same D and alpha as in Model 1. The analytical solutions available for Models 1 and 2, used together with the experimentally derived model parameters D and alpha, allow for easy estimation of drying time and water loss from Poloxamer hydrogel films of various compositions and thicknesses and at different relative humidities. Numerical solutions for water diffusion under conditions of decreasing film thickness and diffusion coefficient being a function of concentration are also presented (Model 3). It becomes apparent from the fit of the data to the different models that the drying rate is more sensitive to the boundary condition at the film-air interface (represented by alpha) than to the diffusion in the film. It is notable that the alpha values obtained from the fits of the Poloxamer hydrogel drying rate are comparable to those obtained from drying of water films under the same experimental conditions.

Diffusion↗
PubMed2005

Hybrid films from blends of chitosan and egg phosphatidylcholine for localized delivery of paclitaxel.

Chitosan and egg phosphatidylcholine (ePC) were used as a unique combination to prepare composite films for localized drug delivery. In comparison to other phospholipids analyzed, ePC was found to produce chitosan-based films with minimal swelling and a high degree of stability. The properties of the chitosan-ePC films were characterized and found to be dependent on the ratio of chitosan:ePC present. FTIR analysis of chitosan-ePC films revealed that their high stability may be attributed to interactions present between these two biomaterials. In vitro evaluation of the cytotoxicity and protein adsorption properties of the films were used to provide a preliminary indication of their biocompatibility. The chitosan-ePC film was also evaluated as a matrix for the localized delivery of the anti-cancer agent, paclitaxel. Nanoparticles containing paclitaxel were dispersed throughout the chitosan-ePC film to result in a drug:material ratio of 1:8 (wt/wt). The film was found to provide a sustained release of paclitaxel over a 4-month period in biologically relevant media. The biological activity of paclitaxel loaded in the chitosan-ePC film was confirmed in SKOV-3 human ovarian cancer cells.

Adsorption↗
PubMed1976

Effect of absorbents on water vapor transmission of free and applied polymer films.

The influence of different types of absorbents on moisture transmission through free (cast films) and applied (coated tablets) polymer films was investigated. In free film studies, lubricated granulations were considered to be the absorbent. The compressed tablet was considered to be the absorbent in applied film studies. The results suggested that, using the same film formulation and film thickness in all cases, the polymer film reduced moisture absorption to the same degree, independent of the absorbent used, suggesting a constant moisture permeation. The results of the free film studies also simulated those of the applied films, allowing the correlation of the data.

Absorption↗
PubMed1979

Progestin permeation through polymer membranes IV: Mechanism of steroid permeation and functional group contributions to diffusion through hydrogel films.

Hydrogel films were prepared from hydroxyethyl methacrylate, both with (Film II) and withouth (Film I) 5.25 mole% of ethylene glycol dimethacrylate. Permeation, diffusion, and partition coefficients for progesterone, testosterone, nandrolone, norethindrone, 17 alpha-hydroxyprogesterone, estradiol, and hydrocortisone were determined. A solute permeation model was proposed based on the separation of a domain (B) composed of "bulk-like" water and a doman (A) composed of polymer, interfacial water, and bound water present in the films. The separate contributions from the "pore" and "solution-diffusion" mechanisms to the total permeability were calculated from the model. Steroid permeabilities through Films I and II were analyzed in accordance with this model. Permeation of Film II occurred via the solution-diffusion mechanism. Permeation of Film I occurred predominately by the pore mechanism with a small contribution (approximate 20%) from the solution-diffusion mechanism. The latter contribution was dependent on the solubility of the solute within the A domains of the hydrogel film. Functional group contributions to permeation of Film II were ascribed to either steric or hydrogen bonding effects.

Diffusion↗
PubMed2004

Polyelectrolyte complex films derived from polyethyleneoxide-maleic acid copolymer and chitosan: preparation and characterization.

Polyelectrolyte complex films were prepared with polyethyleneoxide-maleic acid copolymer and chitosan using a casting/solvent evaporation method. The films were examined in terms of their IR spectra, surface and cross-section morphologies, cytotoxicity, and swelling behavior at different pH levels. To assess the potential of these films as a biomedical device, the profiles of the release of model drug from the CS/PEOMA films were examined at pH 4.8. The surface morphology of the films was quite smooth and uniform, and the cross-sectional morphology was dense and homogeneous. The swelling behaviors of CS/PEOMA films were found to depend on the pH of the solution as well as on the CS/PEOMA composition. Drug release from different CS/PEOMA films at pH 4.8 was found to be dependent on film composition. The results showed the potential applicability of CS/PEOMA film as a drug delivery vehicle.

Absorption↗
PubMed2005

Preparation and characterization of microwave-treated carboxymethyl chitin and carboxymethyl chitosan films for potential use in wound care application.

CM-chitin and CM-chitosan films were successfully crosslinked by microwave treatment. Crosslinking of the microwave-treated CM-chitin films involved mainly the carboxylate and the secondary alcohol groups, while crosslinking of microwave-treated CM-chitosan films involved the carboxylate and the amino groups. In addition, the crystallinity of CM-chitin increased with increasing microwave treatment time, whereas an increase in the crystallinity of the microwave-treated CM-chitosan films was not observed. At a similar percentage of weight loss, the crosslinking of either CM-chitin or CM-chitosan films by microwave treatment required much less stringent condition when compared with the crosslinking by autoclave treatment. Based on both direct and indirect cytotoxicity assays, the cytotoxicity of the microwave-treated CM-chitin films was negative, while that of the microwave-treated CM-chitosan films was positive. Human fibroblasts adhered on the surface of microwave-treated CM-chitosan films much better than on the surface of microwave-treated CM-chitin films.

Animals↗
PubMed1997

Nonlinear Dynamics of Lipid Films under Electric Forces

We study the dynamics and rupture of lipid films perturbed in the symmetric mode squeezing through an electrohydrodynamical approach. The lipid phase and the two surrounding aqueous phases are considered as incompressible Newtonian viscous fluids submitted to van der Waals, steric, and electric body forces. A nonlinear evolution equation for the film thickness, at the long-wavelength limit, is obtained for two symmetric cases: a film with equally charged surfaces with no potential drop and a neutral film submitted to an external electric field. At the long-wavelength limit, the electric term only influences the film evolution when the electric field inside the film is nonvanishing. We solve numerically, as an initial value problem with periodic boundary conditions, the nonlinear evolution equation. The rupture time is obtained and compared with analytical estimates. Sufficiently strong steric forces prevent the film from narrowing beyond a minimum thickness leading the film to a steady state different from the planar one consistently with the nonlinear analytical approach. The presence of a transmembrane electric potential destabilizes the perturbed film as predicted by the linear and nonlinear approaches; however, as expected, destabilization is not relevant at physiological values of the potential drop.

Journal Article↗
PubMed1997

Effect of Lipid Phase State and Foam Film Type on the Properties of DMPG Stabilized Foams

The drainage and stability of DMPG (l -alpha-phosphatidyl-dl -glycerol dimyristoyl) foams were studied by a microconductivity method under conditions where three different foam film types could be formed-thin foam films (TFF), common black foam films (CBF), and Newton black foam films (NBF). Foaming properties were investigated at 20 and 28°C where DMPG is in the gel and liquid-crystalline states. Higher conductivity signals were observed at the higher temperature where DMPG was in the liquid-crystalline state, which is indicative of wetter or more stable foams under these conditions. This effect was observed independent of foam film type. However, for a given phase state, the type of foam films formed significantly influenced the stability and rate of drainage of the foam. Indeed, the water content of the foams, obtained under conditions for formation of different foam films, is ranked in the order TFF > CBF > NBF. When the temperature was increased to 28°C (i.e., in the liquid-crystalline state), CBF and NBF showed a slight decrease in film thickness and an increase in film lifetime and surface molecular diffusion coefficient in the adsorbed layer. It is likely that the fluidity of the interfacial layer is an important factor contributing to DMPG foam stabilization.

Journal Article↗
PubMed1998

Influence of Surfactant Structure on the Drainage of Nonionic Surfactant Foam Films.

The stability of vertical liquid films produced from aqueous solutions of polyoxyethylene alkyl ether (CnEm) was studied by monitoring the dynamic surface tension (gammat) and aqueous core thickness of a vertical foam film (d2) measured by FT-IR. The temperature dependence of the drainage patterns of the liquid films was clarified for CnE8 (n = 10, 12, 14, and 16) solutions. It was found that the critical thickness (Drup) where the film rupture happens increased with increasing temperature in the case of C10E8 and C12E8, while Drup remarkably decreased and finally formed a black film in the case of C14E8 and C16E8 solutions within the measured temperature range. In addition, a delay in the film drainage occurred in these systems, which was caused by the stabilization of the films via the Marangoni effect proved by dynamic surface tension measurements. On the other hand, heterogeneous ethoxylated dodecyl ethers (C12Em) modified with a hydrophilic group showed a remarkable increment of Drup under dynamic conditions without the Marangoni stabilization in the foam film. Adding a hydrophobic group at the end of the polar head produces a large area per molecule and causes a large increase in the surface coverage of the air bubbles. However, a less structured surface coverage facilitated the breaking of the foam during the Ross and Miles test. These results indicate that under dynamic conditions, the Marangoni effect and the hydrophobic interaction at the surface become important for foam film rupture. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Investigation of Polysaccharide Adsorption on Protein Conditioning Films by Attenuated Total Reflection Infrared Spectrometry.

The study of microorganisms at the aqueous/metal interface is of great interest as their presence is often associated with surface deterioration or corrosion. Surfaces submerged in aquatic environments rapidly become fouled with organic macromolecules, such as proteins and/or glycoproteins. Bacteria adhering to this conditioning film typically produce extracellular polysaccharides that anchor the cells to the substrate. In a previous paper, the kinetics of polysaccharide adsorption and desorption on protein conditioning films formed on bare germanium internal reflection elements (IREs) were investigated in an effort to gain a better understanding of the fouling process. This work has been extended to the study of adsorption phenomena at an aqueous/copper interface. Alginic acid and dextran were exposed to protein-conditioned and untreated copper films. In the absence of a protein biofilm, greater erosion of the Cu film was observed with flowing saline than with a solution of alginic acid in saline, and more Cu was removed at pH 4.8 than at pH 7.0. The neutral polysaccharide was less corrosive than alginic acid. The presence of a film of bovine serum albumin (13.5 nm) conditioning film did not shield the Cu film from the corrosive effects of either polysaccharide. In all experiments, as Cu slowly eroded from the surface of the IRE, metal islands formed leading to the observation of surface-enhanced infrared absorption (SEIRA). The intensity of the C-O stretching band of adsorbed dextran on Cu islands was over an order of magnitude greater than would be observed with a uniform Cu film of the same thickness. Enhancement of the amide II band of BSA was also observed. In general, the effect of SEIRA complicated spectral processing and interpretation and thus interfered with the determination of surface coverage and polysaccharide adsorption/desorption kinetics on protein conditioning films. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Aqueous Wetting Films on Fused Quartz.

Using an image analyzing interferometer, IAI, the interfacial characteristics of an isothermal constrained vapor bubble, CVB, in a quartz cuvette were studied as a precursor to heat transfer research. The effects of pH and electrolyte concentration on the meniscus properties (curvature and adsorbed film thickness) and the stability of the aqueous wetting films were evaluated. The surface potential in the electric double layer was a function of the cleaning and hydroxylation of the quartz surface. The disjoining pressure isotherm for pure water was very close to that predicted by the Langmuir equation. For aqueous solutions of moderate electrolyte concentration, the Gouy-Chapman theory provided a good representation of the electrostatic effects in the film. The effect of temperature on the film properties of aqueous solutions and pure water was also evaluated: The meniscus curvature decreased with increasing temperature, while Marangoni effects, intermolecular forces, and local evaporation and condensation enhanced waves on the adsorbed film layer. Pure water wetting films were mechanically metastable, breaking into droplets and very thin films (less than 10 nm) after a few hours. Aqueous wetting films with pH 12.4 proved to be stable during a test of several months, even when subjected to temperature and mechanical perturbations. The mechanical stability of wetting films can explain the reported differences between the critical heat fluxes of pure water and aqueous solutions. The IAI-CVB technique is a simple and versatile experimental technique for studying the characteristics of interfacial systems. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Modeling Draining Flow in Mobile and Immobile Soap Films.

A mathematical model is constructed to describe the two-dimensional flow in a vertical soap film that is draining under gravity. An asymptotic analysis is employed that uses the long-wave or "lubrication" approximation. The modeling results in three coupled partial differential equations that include a number of dimensionless input parameters. The equations are solved numerically. The three functions calculated, as they vary in space and time, are the film thickness, the surface concentration of an assumed insoluble surfactant, and the slip or surface velocity. The film is assumed to be supported by "wire frame" elements at both the top and the bottom; thus the liquid area and the total surfactant are conserved in the simulation. A two-term "disjoining" pressure is included in the model that allows the development of thin, stable, i.e., "black," films. While the model uses a simplified picture of the relevant physics, it appears to capture observed soap film shape evolution over a large range of surfactant concentrations. The model predicts that, depending on the amount of surfactant that is present, the film profile will pass through several distinct phases. These are (i) rapid initial draining with surfactant transport, (ii) slower draining with an almost immobile interface due to the surface tension gradient effect, and (iii) eventual formation of black spots at various locations on the film. This work is relevant to basic questions concerning surfactant efficacy, as well as to specific questions concerning film and foam draining due to gravity. Prospects for extension to three-dimensional soap film flows are also considered. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Hydrodynamic interaction between spheres coated with deformable thin liquid films.

In this article, we considered the hydrodynamic interaction between two unequal spheres coated with thin deformable liquids in the asymptotic lubrication regime. This problem is a prototype model for drop coalescence through the so-called "film drainage" mechanism, in which the hydrodynamic contribution comes dominantly from the lubrication region apart from the van der Waals interaction force. First, a general formulation was derived for two unequal coated spheres that experienced a head-to-head collision at a very close proximity. The resulting set of the evolution equations for the deforming film shapes and stress distributions was solved numerically. The film shapes and hydrodynamic interaction forces were determined as functions of the separation distance, film thickness, viscosity ratios, and capillary numbers. The results show that as the two spheres approach each other, the films begin to flatten and eventually to form negative curvature (or a broad dimple) at their forehead areas in which high lubrication pressure is formed. The dimple formation occurs earlier as the capillary number increases. For large capillary numbers, the film liquids are drained out from their forehead areas and the coated liquid films rupture before the two films "touch" each other. Meanwhile, for small capillary numbers, the gap liquid is drained out first and the two liquid films eventually coalesce.

Journal Article↗
PubMed2006

Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers.

Thin titanium deuteride (TiD(y)) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiD(y) layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiD(y) films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiD(y) films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiD(y) (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiD(y) films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiD(y) film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiD(y) interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiD(y) and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiH(y) film. The XPS valence-band spectra of the Pd/TiD(y) interface reveal electronic features characteristic of a Pd-Ti bimetallic structure.

Journal Article↗
PubMed1998

Determination of erythema-effective solar radiation in Japan and Germany with a spore monolayer film optimized for the detection of UVB and UVA--results of a field campaign.

The available physical and biological broad-band radiometers designed to determine erythema-effective radiation do not show any response or over/underestimate the biologically effective radiation to a high extent in the ultraviolet (UV)A spectral region. The data presented in this paper demonstrate that the biological system used in this study is the first one to make possible measurements of erythema-effective radiation in the sun in the UVA and UVB spectral region. These measurements were performed with a spore-film filter system as well as with spectroradiometers. It was demonstrated that this biotechnological method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested in various field campaigns performed in Germany and in Japan. The seasonal daily variation of UV radiation in Germany determined in the period November 1995 to December 1996 using the spore-film filter system in sunny conditions tallied well with model calculations. The daily dose in Germany measured with the spore-film system close to the summer solstice, in sunny conditions (20.45 MED), was approximately 20 times higher than the lowest value measured close to the winter solstice (0.82 MED), a result which was in accordance with model calculations. The data determined with the spore-film filter system in Sapporo and Naha, Japan, fitted to the erythema-weighted data calculated from spectroradiometric measurements (Brewer), even at low solar radiation angles in a solar spectrum with less UVB but significant UVA. The spore-film dosimeter values were about 103 +/- 8% of the integrated dose of the Brewer instrument. The standard deviation of the spore-film measurements obtained in Japan was 12.8%. The responsivity of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Large Spectrograph with monochromatic radiation. At a wavelength of 365 nm--in a spectral region which is dominant in many tanning lamps and with minor importance for solar radiation in summer conditions--the tested spore-film system gave results that were close (112% compared to the calibration dose) to the calibration dose which was used for irradiation.

Bacillus subtilis↗
PubMed2002

Screen film vs full-field digital mammography: image quality, detectability and characterization of lesions.

The objective of this study was to compare screen-film mammography (SFM) to full-field digital mammography (FFDM) regarding image quality as well as detectability and characterization of lesions using equivalent images of the same patient acquired with both systems. Two mammography units were used, one with a screen-film system (Senographe DMR) and the other with a digital detector (Senographe 2000D, both GEMS). Screen-film and digital mammograms were performed on 55 patients with cytologically or histologically proven tumors on the same day. Together with these, 75 digital mammograms of patients without tumor and the corresponding previous screen-film mammograms not older than 1.5 years were reviewed by three observers in a random order. Contrast, exposure, and the presence of artifacts were evaluated. Different details, such as the skin, the retromamillary region, and the parenchymal structures, were judged according to a three-point ranking scale. Finally, the detectability of microcalcifications and lesions were compared and correlated to histology. Image contrast was judged to be good in 76%, satisfactory in 20%, and unsatisfactory in 4% of screen-film mammograms. Digital mammograms were judged to be good in 99% and unsatisfactory in 1% of cases. Improper exposure of screen-film system occurred in 18% (10% overexposed and 8% underexposed). Digital mammograms were improperly exposed in 4% of all cases but were of acceptable quality after post-processing. Artifacts, most of them of no significance, were found in 78% of screen-film and in none of the digital mammograms. Different anatomical regions, such as the skin, the retromamillary region, and dense parenchymal areas, were better visualized in digital than in screen-film mammography. All malignant tumors were seen by the three radiologists; however, digital mammograms allowed a better characterization of these lesions to the Breast Imaging Reporting and Data System (BI-RADS;) [corrected] categories (FFDM better than SFM in 23 of 165 vs 9 of 165 judged cases in SFM). In conclusion, digital mammography offers a consistent, high image quality in combination with a better contrast and without artifacts. Lesion detection in digital images was equal to that in screen-film images; however, categorization of the lesions to the BI-RADS classification was slightly better.

Adult↗
PubMed2002

In-vitro analysis for microbial barrier properties of 2-octyl cyanoacrylate-derived wound treatment films.

BACKGROUND: In recent years, 2-octyl cyanoacrylate monomer has been formulated for various wound care products that have been approved by the Food and Drug Administration (FDA). PURPOSE: To evaluate the in vitro effectiveness of 2-octyl cyanoacrylate formulation-based films as barriers to various pathogens, including bacteria, fungi, and yeast. METHODS: The barrier properties of the cyanoacrylate films prepared by the following two methods were tested: (1) prepolymerized film and (2) in situ polymerized film. The upper surface of films was inoculated such that the microorganisms would have to penetrate the film to colonize the media beneath. Nine different organisms were used. Plates were observed for growth at two, four, and seven days after inoculation. RESULTS: No growth was observed in any test, with the exception of prepolymerized film challenged with Pseudomonas aeruginosa. The pattern of growth observed suggests that the bacteria colonized the medium by traveling around and not through the film. CONCLUSIONS: 2-Octyl cyanoacrylate-based films are excellent microbial barriers.

Bacteria↗