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PubMed2002

Analytical characterization of thin carbon films.

CH(x) films on silicon substrates deposited by a Mesh Hollow Cathode Process (MHC) were analyzed by various techniques. The films were produced with varying deposition times, resulting in thicknesses ranging from ~2-20 nm. X-Ray Reflectivity (XRR) was used to determine the film thicknesses and the deposition rate. A good correlation of measured XRR thicknesses with SIMS sputter depths down to the film-substrate transition was found. An AFM-based nanoscratching technique was applied to test the wear resistance of the thin overcoats. The MHC films reveal slightly decreasing scratch resistance for reduced film thicknesses, which can be explained by a higher fraction of soft interface zones for thinner films. This is in accordance with Raman spectroscopic measurements in the visible spectral range which were carried out to examine the carbon bonding properties. Combined analysis of G peak position and D/G peak intensity ratio indicates a more graphitic structure for film thicknesses less than 10 nm.

Journal Article↗
PubMed2003

Characterization of nanocrystalline anatase TiO(2) thin films.

Nanoporous thin films were deposited onto glass substrates by painting with a solution of nanocrystalline anatase TiO(2) particles (with a size of either 6 nm or 16 nm) suspended in an organic solvent. Upon drying in air for about 1 day, the films were tempered at 450 degrees C in air for 1 h. This procedure results in stoichiometric TiO(2) films with a thickness of several micro m and a milky whitish appearance. Scanning force microscopy of the surface revealed that the nanoparticles of the films agglomerated into structures with lateral dimensions of some 100 nm. Transmission electron microscopy was utilized to investigate the structural arrangement of the crystallites in the films. High-resolution electron diffraction and X-ray diffraction analyses demonstrated, furthermore, that the material consists exclusively of a single TiO(2) phase, namely anatase, and that the films do not exhibit any preferential texture. The elemental stoichiometry and the possible presence of impurities were monitored throughout the films by means of secondary-ion mass spectrometry depth profiling. Electrical measurements have been carried out as a function of both the sample temperature T and the ambient oxygen partial pressure p(O(2)). From these data the electrical conductivity sigma of the porous films was determined in dependence of those parameters.

Journal Article↗
PubMed1999

Numerical simulations of surface plasmon resonance system for monitoring DNA hybridization and detecting protein-lipid film interactions.

This paper presents a simple method to extract information about thin organic films from surface plasmon resonance (SPR) spectra. From numerical simulations it was found that a shift (delta theta SPR) of an absorption peak in the SPR spectrum was directly proportional to the product of the thin organic film thickness and the refractive index difference between the thin organic film and a buffer soaking the sample. It was also found that delta theta SPR was not sensitive to the thin organic film support of a gold film and a glass cover slip. Relationships between delta theta SPR and distributions of macromolecule structures, in the thin organic films were theoretically established. Formulae were derived for a homemade SPR system to calculate length, transverse area, density and surface concentration of macromolecules in the thin organic film. The validity of these treatments was checked by precisely measuring the size of a single distearoylphosphatidylcholine molecule on a gold-supported phospholipid film; by quantitatively monitoring hybridization of synthesized oligonucleotides strands based on a biotin/avidin system; and by quantitatively detecting the steric hindrance of rabbit C-reactive protein specifically bound to phospholipid monolayers composed of synthesized lipids.

Animals↗
PubMed2002

Performance of a flat-panel detector in the detection of artificial erosive changes: comparison with conventional screen-film and storage-phosphor radiography.

The purpose of this study was to compare a large-area, direct-readout, flat-panel detector system with a conventional screen-film system, a storage-phosphor system, and a mammography screen-film system with regard to the detection of artificial bone erosions simulating rheumatoid disease, and to assess its diagnostic performance with decreasing exposure dose. Six hundred forty regions were defined in 160 metacarpophalangeal and proximal interphalangeal joint specimens from 20 monkey paws (4 regions per joint). Artificial bone erosions were created in 320 of these 640 regions. Specimens were enclosed in containers filled with water to obtain absorption and scatter radiation conditions similar to those of a human hand. Imaging was performed using a flat-panel system, a speed class 200 screen-film system, a mammography screen-film system, and a storage-phosphor system under exactly matched conditions. Different exposure doses equivalent to speed classes of S=100, 200, 400, 800, 1600, and 3200 were used. In all images the presence or absence of a lesion was assessed by three radiologists using a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 21,120 observations (1920 for each imaging modality and exposure level) and diagnostic performance estimated by the area under the ROC curve (A(z)). The significance of differences in diagnostic performance was tested with analysis of variance. The ROC analysis showed A(z) values of 0.809 (S=200), 0.768 (S=400), 0.737 (S=800), 0.710 (S=1600), and 0.685 (S=3200) for the flat-panel system, 0.770 for the speed class 200 screen-film system, 0.781 (S=200), 0.739 (S=400), 0.724 (S=800), 0.680 (S=1600) for the storage-phosphor system, and 0.798 for the mammography screen-film system. Analysis of variance showed significant differences between different combinations of imaging modalities and exposure doses ( p<0.05). The diagnostic performance of the flat-panel detector system is superior to that of a screen-film system and a storage-phosphor system for the detection of erosive lesions at clinical exposure settings (S=200). Using the flat-panel system the exposure dose can be reduced by 50% to obtain a diagnostic performance comparable to a speed class 200 screen-film system.

Animals↗
PubMed2005

Development and characterization of bioadhesive vaginal films of sodium polystyrene sulfonate (PSS), a novel contraceptive antimicrobial agent.

PURPOSE: Polystyrene sulfonate (PSS) is a novel noncytotoxic antimicrobial contraceptive agent. A gel formulation of PSS was found safe for vaginal administration in phase I clinical trials. The purpose of the current study was to develop and evaluate novel bioadhesive vaginal film formulations of PSS. METHODS: PSS films were prepared by solvent evaporation and optimized for various physical, mechanical, and aesthetic properties. Further, films were evaluated for various biological activities and safety. RESULTS: Vaginal films containing 300 mg PSS per unit have been developed, using generally regarded as safe (GRAS) listed excipients. The films are colorless, transparent, thin, soft, and tough, dissolve rapidly in physiologic fluid to form a smooth, viscous and bioadhesive solution that could be retained in the vagina for prolonged intervals. Sperm function inhibition (hyaluronidase and cervical mucus penetration) and antimicrobial activities against human immunodeficiency virus (HIV) and herpes simplex virus (HSV) by PSS films were found comparable to PSS. Also, films did not inhibit normal vaginal microflora (Lactobacillus) and were noncytotoxic as indicated by negligible sperm immobilization and cytotoxicity to host cell assays. CONCLUSIONS: Rapidly dissolving bioadhesive vaginal film formulation of PSS with desired physical, mechanical, aesthetic, and biological properties is a suitable candidate vaginal microbicide for prevention of sexually transmitted disease (STDs) and is ready for toxicological and clinical evaluation.

Animals↗
PubMed1979

Interactions of neomycin with monomolecular films of polyphosphoinositides and other lipids.

The interactions of calcium and the aminoglycosidic antibiotic, neomycin, with various lipids were investigated in monomolecular films. Lipids were spread over a subphase of 0.05 M N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, pH 7.0, and NaCl to give an ionic strength of 0.2. Measurements of surface pressure (pi) were taken with a Wilhelmy balance. In the absence of Ca2+, 1 muM--1 mM neomycin in the subphase decreased pi (i.e. condensed films) of all acidic lipids tested. In the presence of 1 mM Ca2+, neomycin did not change pi of films of phosphatidylserine, phosphatidylinositol and phosphatidic acid while it lowered pi of cardiolipin and cerebroside sulfate films. A unique pattern of interaction was observed with polyphosphoinositide monolayers. In the absence of Ca2+, 1 muM neomycin decreased pi followed by an increase of pi at higher neomycin concentrations. Ca2+ (1 mM) condensed the film significantly more than did neomycin. However, as little as 1 muM neomycin induced expansion of the calcium/lipid film which at 1 mM neomycin reached the same pi as in the absence of Ca2+. Such expansion was observed at all pressures of the film including the collapse pressure indicating a strong 'complex' between the drug and polyphosphoinositide not antagonized by Ca2+. In the absence of possible hydrophobic interactions, both the condensation and the expansion of the film should be mediated by ionic forces. Combined in vivo and in vitro evidence is discussed to suggest the polyphosphoinositides as the physiological receptors for aminoglycosides in the mammalian cell membrane.

Calcium↗
PubMed1984

Electron microscopy of fine fibrin clots and fine and coarse fibrin films. Observations of fibers in cross-section and in deformed states.

Fine fibrin clots and coarse and fine fibrin films (both ligated and unligated), formed by shrinkage of clots in one dimension, were examined by electron microscopy. Specimens of clots were prepared by critical point drying and by embedding and sectioning; specimens of films were prepared by embedding and sectioning only. In the fine clots, network junctions appeared to be formed by fiber segments in which two or more protofibrils were gently twisted around each other for distances of the order of 200 nm and then diverged to give trifunctional branch points. This topology appeared to be preserved in the fine films. It is proposed that the strength of the junctions is primarily provided by the twisting topology, though reinforced by non-covalent bonding involving the B sites uncovered by thrombin. In coarse films, bundles of protofibrils, lying primarily in the film plane, had diameters of 40 to 200 nm and were gently twisted around each other to form thicker cables. Uniaxial stretching, up to 100%, of either fine or coarse film before fixing caused suprisingly extensive orientation of the protofibrils or bundles. However, random orientation was recovered if a stretched ligated film was allowed to retract to its original dimensions before fixing. In a stretched coarse film sectioned perpendicular to the stretch direction, fiber bundles could be seen in cross-section; these were roughly circular with scalloped edges. The changes with stretching and recovery are discussed in relation to possible mechanisms of deformation and elastic energy storage.

Animals↗
PubMed1976

A study of the resolution of dental films and screens.

From the study of the resolution produced by 156 screen-film combinations at a film density between 1.41 and 1.59, the following conclusions are drawn: 1. Resolution is affected by screens, films, and observers. 2. The effect of screens on resolution is much greater than the effect of films. 3. Screens varied greatly in resolving ability. 4. Films did not differ greatly in resolving ability. 5. Cronex Lightning Plus screen and Radelin super high-speed screen produced the lowest resolution and Cronex detail screen produced the highest resolution. 6. In general, the slower the screen, the higher is the resolution and vice versa. 7. There were two groups of films with significant resolution differences. 8. Films designed to be processed automatically did not differ significantly in their resolving ability when processed manually. 9. There is significant interaction effect of screens and films on resolution. 10. Individual visual resolving ability plays a significant role in measuring resolution.

Radiographic Image Enhancement↗
PubMed1996

Pre-conditioning and dual constant composition dissolution kinetics of pulsed laser deposited hydroxyapatite thin films on silicon substrates.

The kinetics of dissolution of pulsed laser deposited crystalline and amorphous thin films of hydroxyapatite on silicon substrates were measured at 37 degrees C and a pH value of 6.5 using the dual constant composition method. Solutions in which the pulsed laser deposited films were pre-conditioned (0.15 M NaCl) remained undersaturated or slightly supersaturated with respect to hydroxyapatite after equilibrium was reached, indicating only a very small coating release and the absence of re-precipitation on the surfaces. The amorphous films released more calcium and phosphate during pre-conditioning than the more crystalline films. Dual constant composition dissolution rates decreased as film crystallinity increased. The film with the lowest dissolution rate (approximately one sixth that of a crystalline film deposited using a hydroxyapatite powder target) was fabricated using a human tooth as the laser target. During pre-conditioning of plasma-sprayed coatings, more calcium and phosphate were released than for pulsed laser deposited films, and dual constant composition dissolution rates were much higher.

Calcium Phosphates↗
PubMed1990

Reproducibility of mantle irradiation with daily imaging films.

Daily mantle imaging films were reviewed to evaluate the accuracy of daily treatments for 28 de novo patients with Hodgkin's disease treated with curative intent between September 1978 and September 1983. Each film was compared with the original simulation film by three independent observers. Each observer graded each film for accuracy in the superior mediastinal, axillary, and inferior mediastinal areas and for overall conformity to the treatment plan. Grades ranged from 1 to 3: grade 1 denoted accuracy within +/- 0.5 cm of the treatment plan, grade 2 denoted minor deviations greater than 0.5 cm but with no tumor or prophylactic treatment areas shielded, and grade 3 denoted an unacceptable setup. The results in 28 patients (1,186 films) showed that 84% of the films were within 0.5 cm of original plan, 15% had minor deviations, and 1% were considered unacceptable. Three patients in the study developed recurrence of Hodgkin's disease in the chest. In one of these patients, 4 of 40 films were unacceptable, but recurrence was in lung parenchyma in an area not designated for treatment. Errors in treatment setup in this small sample were not a factor in the likelihood of disease recurrence in the chest. Daily imaging films have helped decrease the number of minor deviations and unacceptable setups, compared with previous experiences.

Diagnostic Imaging↗
PubMed1993

Objective decision-making following a portal film: the results of a pilot study.

PURPOSE: To discriminate between random and systematic treatment setup errors using portal films. METHODS AND MATERIALS: A bi-dimensional analytic techniques using multiple analyses of variance based on Hotelling's T2 statistics to derive numerical and graphical measures of daily portal film accuracy and precision has been trialed using 88 daily portal films from seven patients' treatment. RESULTS: A demonstration is provided of how a reasonable approximation of random variation from the intended (Simulator) field center, and systematic displacement of the mean position of the portal film centers may be derived from a minimum number of portal films. If a random error as great as 10 mm exists, at least six or seven portal films are considered necessary to reliably detect and quantify the size of a systematic error. CONCLUSION: Our results suggest that a modest systematic error could go undetected until the end of a 5 or 6 week course of treatment if only one portal film is obtained each week. A greater number of portal films should be performed during the first week of treatment to reduce the frequency of such errors. Efforts to separate and quantify both random and systematic errors in setup are worthwhile and will lead to improvements in outcome at the individual patient level and at a departmental level in the development of quality assurance programs.

Humans↗
PubMed1996

Functionalisation of Si/SiO2 and glass surfaces with ultrathin dextran films and deposition of lipid bilayers.

Dextran with molecular weight of 500 kDalton was covalently coupled to glass and Si/SiO2-surfaces by epoxy functionalisation or by photo reactive functionalisation of the solid surface. With the described methods we can control the deposited mass density between 0.3 and 4.8 ng/m2 corresponding to mean film thicknesses of a dry dextran film between 2 A and 30 A. We studied the structural properties (thickness, density) of ultrathin dextran layers coupled to silicon wafers of glass surfaces in humid atmosphere and under water by ellipsometry and reflection interference contrast microscopy (RICM) and developed a new method to measure the interfacial forces in ultrathin films. We demonstrate, that these hydrophilic polymer films from soft cushions which can be reversibly swollen both under water and in humidified air. In water the films swell up to thicknesses of about 600 to 800 A as measured by reflection interference contrast microscopy (RICM) and ellipsometry. The interaction of the polymer films with Si/SiO2-surfaces in contact with humidified air was studied by ellipsometry. We measured the thickness of the polymer layers as a function of the relative humidity of the atmosphere surrounding the sample in a hydration chamber. Depending on the humidity of the surrounding air and induced by the hydration the film thickness changes by about a factor of 10. Coupling of N-hydroxysuccinimide to dextran enables the functionalisation of the dextran cushions with a broad range of different specific binding molecules for various detection tasks. The possibility of soft hydrated dextran films as a cushion for the deposition of self healing lipid bilayers is shown.

Biocompatible Materials↗
PubMed1990

An assessment of a film enhancement system for use in a radiation therapy department.

The clinical uses of a radiotherapy film enhancement system are explored. The primary functions of the system are to improve the quality of poorly exposed simulator and portal films, and to perform comparisons between the two films to determine whether patient or block positioning errors are present. Other features include: the production of inexpensive, high quality hardcopy images of simulation films and initial portal films for chart documentation, the capacity to overlay lateral simulation films with sagittal MRI films to aid in field design, and a mode to zoom in on individual CT or MRI images and enlarge them for video display during chart rounds or instructional sessions. This commercially available system is comprised of a microcomputer, frame grabber, CCD camera with zoom lens, and a high-resolution thermal printer. The user-friendly software is menu driven and utilizes both keyboard and track ball to perform its functions. At the heart of the software is a very fast Adaptive Histogram Equalization (AHE) routine, which enhances and improves the readability of most portal films. The system has been evaluated for several disease sites, and its advantages and limitations will be presented.

Humans↗
PubMed2004

Heme protein films with polyamidoamine dendrimer: direct electrochemistry and electrocatalysis.

Biocompatible nanosized polyamidoamine (PAMAM) dendrimer films provided a suitable microenvironment for heme proteins to transfer electron directly with underlying pyrolytic graphite (PG) electrodes. Hemoglobin (Hb), myoglobin (Mb), horseradish peroxidase (HRP), and catalase (Cat) incorporated in PAMAM films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. While Hb-, Mb-, and HRP-PAMAM films showed the cyclic voltammetry (CV) peaks at about -0.34 V vs. saturated calomel electrode (SCE) in pH 7.0 buffers, Cat-PAMAM films displayed the peak pair at a more negative potential of -0.47 V. The protein-PAMAM films demonstrated a surface-confined or thin-layer voltammetric behavior. The electrochemical parameters such as apparent heterogeneous electron transfer rate constants (k(s)) and formal potentials (E (degrees ')) were estimated by square wave voltammetry with nonlinear regression analysis. UV-vis and IR spectroscopy showed that the proteins retained their near-native secondary structures in PAMAM films. Oxygen, hydrogen peroxide, and nitrite were catalytically reduced at the protein-PAMAM film electrodes, showing the potential applicability of the films as the new type of biosensors or bioreactors based on direct electrochemistry of the proteins.

Bioreactors↗
PubMed2006

Effect of humidity on the stability of lung surfactant films adsorbed at air-water interfaces.

The effect of humidity on the film stability of Bovine Lipid Extract Surfactant (BLES) is studied using the captive bubble method. It is found that adsorbed BLES films show distinctly different stability patterns at two extreme relative humidities (RHs), i.e., bubbles formed by ambient air and by air prehumidified to 100% RH at 37 degrees C. The differences are illustrated by the ability to maintain low surface tensions at various compression ratios, the behavior of bubble clicks, and film compressibility. These results suggest that 100% RH at 37 degrees C tends to destabilize the BLES films. In turn, the experimental results indicate that the rapidly adsorbed BLES film on a captive bubble presents a barrier to water transport that retards full humidification of the bubble when ambient air is used for bubble formation. These findings necessitate careful evaluation and maintenance of environmental humidity for all in vitro assessment of lung surfactants. It is also found that the stability of adsorbed bovine natural lung surfactant (NLS) films is not as sensitive as BLES films to high humidity. This may indicate a physiological function of SP-A and/or cholesterol, which are absent in BLES, in maintaining the extraordinary film stability in vivo.

Adsorption↗
PubMed2005

An electrochemical investigation of hemoglobin and catalase incorporated in collagen films.

Collagen, an electrochemically inert protein, formed films on pyrolytic graphite (PG) electrodes, which provided a suitable microenvironment for heme proteins to transfer electron directly with the underlying electrodes. Hemoglobin (Hb) and catalase (Cat) incorporated in collagen films exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks at around -0.35 V and -0.47 V (vs. SCE) in pH 7.0 buffers, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. UV-vis spectra showed that the heme proteins in collagen films retained their near-native conformations in the medium pH range. The results of scanning electron microscopy (SEM) demonstrated that the interaction between heme proteins and collagen made the morphology of dry protein-collagen films different from the collagen films alone. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E degrees ') of the films were estimated by using square wave voltammograms (SWV) and nonlinear regression analysis. The heme protein-collagen film electrodes were also used to catalyze the reduction of nitrite, oxygen and hydrogen peroxide, indicating potential applications of the films for the fabrication of a new type of biosensor that does not use mediators.

Animals↗
PubMed2004

Controlled release of ethacrynic acid from poly(lactide-co-glycolide) films for glaucoma treatment.

Ethacrynic acid (ECA) is a potential glaucoma drug that can reduce intraocular pressure. However, conventional methods of ECA administration may cause toxicity to normal eye tissues and are inconvenient to patients. Therefore, we developed and characterized an ECA loaded poly(lactide-co-glycolide) (PLGA) copolymer film, and quantified the therapeutic efficacy of the film implanted in the rabbit eye. In the aqueous medium, the release of ECA from the PLGA50:50 film was time dependent and more than 90% of ECA was released within a week. This release profile was consistent with the kinetics of water uptake and microstructural changes of PLGA50:50 films as revealed by an electron microscopy examination. ECA release and PLGA degradation caused a gradual pH decrease in the release medium. The total pH decrease was 0.4 unit in 3 days. We also observed that the initial rate of ECA release was positively correlated with the weight ratio of ECA versus PLGA and inversely correlated with the molar ratio of lactide versus glycolide in PLGA films. At the end of a 3-day incubation, the cumulative release of ECA from PLGA50:50, PLGA85:15 and PLGA100:00 films were 78.8%, 9.35% and 3.60%, respectively. When the PLGA50:50 film loaded with ECA was implanted into the sclera of rabbit eyes, the intraocular pressure was significantly reduced and the reduction was maintained for at least 10 days. These data indicate that PLGA films have a potential to be used as a controlled ECA release device for glaucoma treatment.

Absorption↗
PubMed2005

Natural polyelectrolyte films based on layer-by layer deposition of collagen and hyaluronic acid.

The aim of the present work was to assemble extracellular matrix components into polyelectrolyte multilayers using the layer-by-layer deposition method. The films are constructed with type-I collagen and hyaluronic acid. The construction exhibits the general features observed during polyelectrolyte multilayer buildup: alternate positive and negative values of the zeta potential of the film during its construction and regular increase of the film thickness with the number, n, of deposition step. This increase is shown to be linear with n. As expected for a linearly growing film, the confocal microscopy shows that when the film is brought in contact with a collagen solution, collagen does not diffuse into the film but interacts only with its outer layer. However, the films are not constituted of homogeneously distributed polyanion/polycation complexes as it is usually observed, but they are formed of fibers as imaged by AFM. The typical width of these fibers increases with the number of deposition steps. Finally, it is found that chondrosarcoma cells spread well and synthesize extracellular matrix components only on the collagen ending films, whereas no cellular matrix was found for HA ending ones. Such architectures may be further functionalized by inclusion of active drugs, peptides, proteins..., and could be used as tunable biomaterial interfaces.

Biocompatible Materials↗