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PubMed1990

[Structure of medical X-ray films].

Characteristic comparisons were made on various medical and dental X-ray films such as Agfa-Gevart, Dupont, Hanshin, Kodak, Konica, Nix, Sun Dental film. 1) Silver grains coated on the film base of regular and dental films showed a round (polyhedron) or potato-like shape. Grains of orthochromatic films were hexagonal or triangular in shape, although those of Konica orthochromatic films were small and round. 2) Size of silver grains ranged from 1.09 microns in the Fuji HRS film to 2.09 microns in the Konica film. 3) Thickness of the film base was the same (170 microns) in all types of film. 4) Thickness of the emulsion layer was 7 microns for non-screen type film, whereas that in the screen type was 4 microns to 8 microns. 5) Size of the silver grain of Kodak Ekta speed was large, and the thickness of the emulsion of this film was thin when compared to others. 6) In screen type films, the silver grains were only sparsely coated. In the non-screen type, however, a large number of silver grains were coated compactly on the film base. 7) Kodak TMG (T-mat) showed flattened silver grains which were piled up on the film layer.

Radiography, Dental↗

PubMed2006

Microstructural imaging and characterization of the mechanical, chemical, thermal, and swelling properties of starch-chitosan blend films.

Chitosan has wide range of applications as a biomaterial, but barriers still exist to its broader use due to its physical and chemical limitations. The present study evaluated the properties of the polymeric blend films obtained from chitosan and potato starch by the casting/solvent evaporation method. The swelling properties of the different films studied as a function of pH showed that the sorption ability of the blend films increased with the increasing content of starch. Fourier transform infrared (FTIR) analyses confirmed that interactions were present between the hydroxyl groups of starch and the amino groups of chitosan in the blend films while the x-ray diffraction (XRD) studies revealed the films to exhibit an amorphous character. Thermogravimetric analyses showed that in the blend films, the thermal stability increased with the increasing starch content and the stability of starch and chitosan powders reduced when they were converted to film. The differential scanning calorimetry (DSC) studies revealed an endotherm corresponding to water evaporation around 100 degrees C in all the films and an exotherm, corresponding to the decomposition in the chitosan and blend films. Scanning electron microscopy (SEM) observations indicated that the blend films were less homogenous and atomic force microscopy (AFM) studies revealed the chitosan films to be smooth and homogenous, while the starch films revealed characteristic granular pattern. The blend films exhibited an intermediate character with a slight microphase separation. The starch-chitosan blend films exhibited a higher flexibility and incorporation of potato starch into chitosan films improved the percentage elongation.

Chitosan↗

PubMed2001

Brand appearances in contemporary cinema films and contribution to global marketing of cigarettes.

BACKGROUND: The appearance of a cigarette brand in a cinema film gives the brand a certain distinction through its association with the characters and general tone of the film. Through the worldwide distribution of films, brands are promoted globally. We assessed the tobacco-brand appearances in a 10-year sample of contemporary films. METHODS: We viewed the contents of the top 25 US box-office films for each year of release, from 1988 to 1997 (250 films in total). We compared the prevalence of brand appearances for films produced before a voluntary ban on paid product placement by the tobacco industry (1988-90) with films produced after the ban (1991-97). Tobacco-brand appearance was defined as the screen appearance of a brand name, logo, or identifiable trademark on products or product packaging, billboards, store-front advertising, or tobacco promotional items. We defined actor endorsement of a brand as the display of a brand while being handled or used by an actor. FINDINGS: More than 85% of the films contained tobacco use. Tobacco brands appeared in 70 (28%) films. Brand appearances were as common in films suitable for adolescent audiences as they were in films for adult audiences (32 vs 35%), and were also present in 20% of those rated for children. Prevalence of brand appearance did not change overall in relation to the ban. However, there was a striking increase in the type of brand appearance depicted, with actor endorsement increasing from 1% of films before the ban to 11% after. Four US cigarette brands accounted for 80% of brand appearances. Revenues outside the USA accounted for 49% of total revenues for these films, indicating a large international audience. INTERPRETATION: Tobacco-brand appearances are common in films and are becoming increasingly endorsed by actors. The most highly advertised US cigarette brands account for most brand appearances, which suggests an advertising motive to this practice.

Female↗

PubMed1998

Formation and structure of surface films: captive bubble surfactometry.

The adsorption model for soluble surfactants has been modified for suspensions of pulmonary surfactant. The dynamic adsorption behavior may be governed by a two-step process: (1) the transfer of molecules between the surface layer and the subsurface layer, which has a thickness of a few molecular diameters only; (2) the exchange of molecules between the subsurface and the bulk solution. The first step is an adsorption process and the second step is a mass transfer process. Between the subsurface and the bulk solution is an undisturbed boundary layer where mass transport occurs by diffusion only. The thickness of this boundary layer may be reduced by stirring. Rapid film formation by adsorption bursts from lipid extract surfactants, as observed in the captive bubble system, suggests that the adsorption process as defined above is accompanied by a relatively large negative change in the free energy. This reduction in the free energy is provided by a configurational change in the association of the specific surfactant proteins and the surfactant lipids during adsorption. The negative change in the free energy during film formation more than compensates for the energy barrier related to the film surface pressure. In the traditional view, the extracellular alveolar lining layer is composed of two parts, an aqueous subphase and a surfactant film, believed to be a monolayer, at the air-water interface. The existence and continuity of the aqueous subphase has recently been demonstrated by Bastacky and coworkers, and a continuous polymorphous film has recently been shown by Bachofen and his associates, using perfusion fixation of rabbit lungs with slight edema. In the present chapter, we have described a fixation technique using a non-aqueous fixation medium of perfluorocarbon and osmium tetroxide to fix the peripheral airspaces of guinea pig lungs. A continuous osmiophilic film which covers the entire alveolar surface, including the pores of Kohn, is demonstrated. By transmission electron microscopy, the surface film frequently appears multilaminated, not only in the alveolar corners or crevices, but also at the thin air-blood barrier above the capillaries. Disk-like structures or multilamellar vesicles appear partially integrated into the planar multilayered film. In corners and crevices, tubular myelin appears closely associated with the surface film. Tubular myelin, however, is not necessary for the generation of a multilaminated film. This is demonstrated in vitro by the fixation for electron microscopy of a film formed from lipid extract surfactant on a captive bubble. Films formed from relatively high surfactant concentration (1 mg/ml of phospholipid) are of variable thickness and frequent multilayers are seen. In contrast, at 0.3 mg/ml, only an amorphous film can be visualized. Although near zero minimum surface tensions can be obtained for both surfactant concentrations, film compressibility and mechanical stability are substantially better at the higher concentrations. This appears to be related to the multilaminated structure of the film formed at the higher concentration.

Adsorption↗

PubMed2005

Functional properties of edible agar-based and starch-based films for food quality preservation.

Edible films made of agar (AG), cassava starch (CAS), normal rice starch (NRS), and waxy (glutinous) rice starch (WRS) were elaborated and tested for a potential use as edible packaging or coating. Their water vapor permeabilities (WVP) were comparable with those of most of the polysaccharide-based films and with some protein-based films. Depending on the environmental moisture pressure, the WVP of the films varies and remains constant when the relative humidity (RH) is >84%. Equilibrium sorption isotherms of these films have been measured; the Guggenheim-Anderson-de Boer (GAB) model was used to describe the sorption isotherm and contributed to a better knowledge of hydration properties. Surface hydrophobicity and wettability of these films were also investigated using the sessile drop contact angle method. The results obtained suggested the migration of the lipid fraction toward evaporation surface during film drying. Among these polysaccharide-based films, AG-based film and CAS-based film displayed more interesting mechanical properties: they are transparent, clear, homogeneous, flexible, and easily handled. NRS- and WRS-based films were relatively brittle and have a low tension resistance. Microstructure of film cross section was observed by environmental scanning electron microscopy to better understand the effect of the structure on the functional properties. The results suggest that AG-based film and CAS-based films, which show better functional properties, are promising systems to be used as food packaging or coating instead of NRS- and WRS-based films.

Agar↗

PubMed2005

Molecular ordering and 2D conductivity in ultrathin poly(3-hexylthiophene)/gold nanoparticle composite films.

This paper reports the first comparison of the structure and electrical conductivity properties of spin cast (SC) and Langmuir-Schaeffer (LS) films of regioregular poly(3-hexylthiophene) (P3HT). In addition, the effect of incorporating highly monodisperse Au nanoparticles (NPs), with a core diameter of approximately 5 nm, into SC and LS P3HT films is described. A detailed picture of molecular organization in the films has been obtained using ultraviolet-visible absorption spectroscopy, atomic force microscopy, field-emission scanning electron microscopy, X-ray diffraction, and X-ray reflectivity. Film morphology was correlated with pseudo-two-dimensional conductivity measured using scanning electrochemical microscopy, with P3HT in the semiconducting regime. It was found that SC films, which were slightly thicker than those formed with the LS technique, exhibited greater organization. This resulted in an order of magnitude higher lateral conductivity for the SC films. Inclusion of Au NPs (50 wt %) into both SC and LS films resulted in the formation of uniform and relatively flat (rms roughness approximately 1 nm) composite films. Surprisingly, the addition of NPs did not disrupt the characteristic crystal structure found for the native P3HT films. The effect of Au NPs on film lateral conductivity was found to be determined by the distribution of Au NPs within the polymer, which varied significantly between SC and LS films. Whereas Au NPs aggregated into hexagonally packed clusters in SC films, NPs in LS films were predominantly uniformly distributed between the lamella bilayer. It was found that, while the inclusion of Au NPs caused the lateral conductivity to decrease in SC films, in LS films, the lateral conductivity increased by a factor of 2.

Journal Article↗

PubMed2005

Biocomposite films synthesized at a fluid/fluid interface.

In the synthesis of mesostructured particles and films, the cooperative self-organization of amphiphilic molecules in the presence of reactive species is a key factor in the reaction mechanism. This paper presents a method for preparing structured collagen films synthesized at fluid/fluid interfaces. This work is an extension of previous efforts in our group to synthesize structured silica films in a reaction system confined at the interface between two immiscible fluid phases, providing an additional level of control over the structural evolution that occurs during reaction. Synthesis at a liquid/liquid interface was shown to provide excellent control over the mesostructure of the final product, avoiding a major problem encountered in many film synthesis techniques in which the reaction occurs at a liquid/solid interface: namely, the undesired effect of the solid surface on the film structure. The focus of this paper is the synthesis of structured composite films containing amphiphilic phospholipids and collagen. These films provide a way to pattern cell growth on biocompatible surfaces and a model system for studying the self-assembly mechanism of lipids and collagen. Self-assembled monolayers and bilayers composed of phosphatidylethanolamine (PE) lipids and collagen were investigated to determine how regularly patterned films can be prepared in a manner that preserves the bioactive properties of the collagen. Mixtures of PEs and acid-soluble collagen were spread on an aqueous subphase in a Langmuir trough. Surface pressure-area compression isotherms for the composite lipid/collagen monolayers provide information about interactions between these components. Langmuir-Blodgett (LB) techniques were utilized to transfer the composite films onto freshly cleaved mica. The mica-supported films were characterized by atomic force microscopy. The lipid/collagen ratio in the composite films was found to be the most important factor in determining how the collagen is assembled and distributed. The temperature and pH of the aqueous subphase, the process for spreading collagen on the subphase, the deposition speed, and the deposition pressure are factors that can be used to selectively control the film patterning. For most of these experimental factors, the range over which a highly structured uniform film can be fabricated over significant length scales is generally very narrow. Based on the experimental results and understanding of the fundamental interactions involved, a mechanism for the co-self-assembly of phospholipids and collagen is suggested. The adhesion and growth of Chinese hamster ovary (CHO) cells on the patterned film surfaces demonstrates the biocompatibility of these composite films.

Animals↗

PubMed2005

Action of particle films on the biology and behavior of pear psylla (Homoptera: Psyllidae).

Particle films with different properties have been developed for arthropod pest control. Two basic film types are hydrophobic and hydrophilic films. The hydrophilic film formulations differ in the amount and kind of spreader-sticker that is incorporated into the kaolin particles. The effects of particle film type (hydrophobic versus hydrophilic) and formulation (Surround versus Surround WP) on the biology and behavior of pear psylla, Cacopsylla pyricola (Foerster), were investigated on pear in a series of laboratory studies. Scanning electron microscopy determined that the number of particles that attached to the front tibia of adult psylla differed by particle formulation but the particle sizes were fairly uniform and ranged from 3.6 to 4.5 microm in diameter. Adults had difficulty grasping particle film-treated leaves, and this effect was influenced by film type and leaf surface. Choice and no-choice tests indicated that adult settling and oviposition were very low, regardless of film type or formulation. Under no-choice conditions, adult mortality was low, in part, because the adults were able to feed through all 3% particle films, but at reduced rates. However, the mortality of adults sprayed with 3% particle film solutions ranged from 22.2 to 62.5% within 72 h after treatment, and mortalities differed most between the hydrophilic formulations. Nymphs born on particle film-treated foliage incurred high mortalities ranging from 58.9 to 82.0% by the time they reached the fifth instar and were affected most by particle film type. Nymphal development was not affected by particle film type or formulation. Egg fertility and nymphal hatch also were unaffected by particle films. These studies determined that there are a number of biological effects particle films have on pear psylla beyond the deterrence of adult settling and oviposition.

Animals↗

PubMed1998

Incorporation of food-grade antimicrobial compounds into biodegradable packaging films.

Lysozyme and nisin are both antimicrobial proteins effective against gram-positive bacteria. The use of these antimicrobials in combination with chelating agents displays increased effectiveness against gram-negative bacteria. Packaging films with lysozyme or nisin incorporated into the film structure were tested separately for inhibition against Lactobacillus plantarum. Both lysozyme and nisin were used in combination with EDTA in films and were evaluated for inhibition against Escherichia coli. Two packaging film-forming methods were used to incorporate lysozyme or nisin into biodegradable protein films to determine if antimicrobial properties could be induced in the film. Heat-press and casting methods were used to produce films made from soy protein and corn zein. Circular samples were cut from the finished films, which were then placed on a bacterial lawn, incubated, and measured for any zones of inhibition. Both cast and heat-press films with added lysozyme or nisin formed excellent films and exhibited inhibition of bacterial growth. The lysozyme and nisin retained their bacteriocidal properties throughout both the heat-press and cast film-forming processes. The cast films exhibited larger inhibitory zones, as compared to the heat-press films, when the same levels of lysozyme or nisin were incorporated. L. plantarum was inhibited by films containing nisin or lysozyme. The addition of EDTA increased the inhibitory effect of films against E. coli.

Anti-Bacterial Agents↗

PubMed2001

[Research on the resistivity of the HFCVD diamond films].

Resistivity of the diamond films by HFCVD technology is analyzed and studied. The I-V curve of the film is depicted in vertical direction using electrode of aluminum film plated on the surface of the diamond films. Further the resistivity of the films is determined. The following conclusion is derived on the basis of the analysis of Raman, SEM and XRD. The resistivity of the diamond films is in relation to the size of the grains and grain orientation of the surface of the films. The larger in average the grain of the films has, the greater the resistivity of the films is. Besides, the film with grain orientation of (110) has a larger resistivity. In addition, the fewer the defect and impurity of the film has, the larger the resistivity of the films is. Therefore, it is important to add the grain size of the film in average, and to increase the grain orientation rate of (110)/(111) in order to gain diamond films that have larger resistivity and good property of insulation. To reduce the content of structure defect and impurity is also an effect way to raise the resistivity of the films.

Aluminum↗

PubMed2002

Dosimetry of therapeutic photon beams using an extended dose range film.

For intensity modulated radiation therapy (IMRT) dose distribution verification, multidimensional measurements are required to quantify the steep dose-gradient regions. High resolution, two-dimensional dose distributions can be measured using radiographic film. However, the photon energy response of film is known to be a function of depth, field size, and photon beam energy, potentially reducing the accuracy of dose distribution measurements. The dosimetric properties of the recently developed Kodak EDR2 film were investigated and compared to those of Kodak XV film. The dose responses of both film types to 6 MV and 18 MV photon beams were investigated for depths of 5 cm, 10 cm, and 15 cm and field sizes of 4x4 cm2 and 15x15 cm2. This analysis involved the determination of sensitometric curves for XV and EDR2 films, the determination of dose profiles from exposed XV and EDR2 films, and comparison of the film-generated dose profiles to ionization chamber measurements. For the combinations of photon beam energy, depth, and field size investigated here, our results indicate that the sensitometric curves are nearly independent of field size and depth of calibration. For a field size of 4x4 cm2, a single sensitometric curve for either EDR2 and XV film can be used for the determination of relative dose profiles. For the larger field size, the sensitometric curve for EDR2 film is superior to XV film in regions where the dose falls below 20% of the central axis dose, due to the effects that the increased low energy scattered photon contributions have on film response. The limited field size and depth dependence of sensitometric data measured using EDR2 film, along with the inherently wide linear dose-response range of EDR2 film, makes it better suited to the verification of IMRT dose distributions.

Calibration↗

PubMed2004

Effect of processing time delay on the dose response of Kodak EDR2 film.

Kodak EDR2 film is a widely used two-dimensional dosimeter for intensity modulated radiotherapy (IMRT) measurements. Our clinical use of EDR2 film for IMRT verifications revealed variations and uncertainties in dose response that were larger than expected, given that we perform film calibrations for every experimental measurement. We found that the length of time between film exposure and processing can affect the absolute dose response of EDR2 film by as much as 4%-6%. EDR2 films were exposed to 300 cGy using 6 and 18 MV 10 x 10 cm2 fields and then processed after time delays ranging from 2 min to 24 h. An ion chamber measured the relative dose for these film exposures. The ratio of optical density (OD) to dose stabilized after 3 h. Compared to its stable value, the film response was 4%-6% lower at 2 min and 1% lower at 1 h. The results of the 4 min and 1 h processing time delays were verified with a total of four different EDR2 film batches. The OD/dose response for XV2 films was consistent for time periods of 4 min and 1 h between exposure and processing. To investigate possible interactions of the processing time delay effect with dose, single EDR2 films were irradiated to eight different dose levels between 45 and 330 cGy using smaller 3 x 3 cm2 areas. These films were processed after time delays of 1, 3, and 6 h, using 6 and 18 MV photon qualities. The results at all dose levels were consistent, indicating that there is no change in the processing time delay effect for different doses. The difference in the time delay effect between the 6 and 18 MV measurements was negligible for all experiments. To rule out bias in selecting film regions for OD measurement, we compared the use of a specialized algorithm that systematically determines regions of interest inside the 10 x 10 cm2 exposure areas to manually selected regions of interest. There was a maximum difference of only 0.07% between the manually and automatically selected regions, indicating that the use of a systematic algorithm to determine regions of interest in large and fairly uniform areas is not necessary. Based on these results, we recommend a minimum time of 1 h between exposure and processing for all EDR2 film measurements.

Film Dosimetry↗

PubMed2006

Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification.

The quantitative dose validation of intensity-modulated radiation therapy (IMRT) plans require 2-dimensional (2D) high-resolution dosimetry systems with uniform response over its sensitive region. The present work deals with clinical use of commercially available self-developing Radio Chromic Film, Gafchromic EBT film, for IMRT dose verification. Dose response curves were generated for the films using a VXR-16 film scanner. The results obtained with EBT films were compared with the results of Kodak extended dose range 2 (EDR2) films. The EBT film had a linear response between the dose range of 0 to 600 cGy. The dose-related characteristics of the EBT film, such as post irradiation color growth with time, film uniformity, and effect of scanning orientation, were studied. There was up to 8.6% increase in the color density between 2 to 40 hours after irradiation. There was a considerable variation, up to 8.5%, in the film uniformity over its sensitive region. The quantitative differences between calculated and measured dose distributions were analyzed using DTA and Gamma index with the tolerance of 3% dose difference and 3-mm distance agreement. The EDR2 films showed consistent results with the calculated dose distributions, whereas the results obtained using EBT were inconsistent. The variation in the film uniformity limits the use of EBT film for conventional large-field IMRT verification. For IMRT of smaller field sizes (4.5 x 4.5 cm), the results obtained with EBT were comparable with results of EDR2 films.

Dose-Response Relationship, Radiation↗

PubMed2002

Dosimetric performance of an enhanced dose range radiographic film for intensity-modulated radiation therapy quality assurance.

Film-based quality assurance (QA) is an important element of any intensity modulated radiation therapy (IMRT) program. XV2 film is often used for IMRT QA, however, it has saturation and energy response limitations which hinder accurate film dosimetry. A new commercially released ready-pack film has been introduced that has an extended dose range (EDR2), reportedly allowing measured doses above 600 cGy without saturation. Also, this film may have less energy dependence due to its composition. The purpose of this paper is to study and compare the two types of film with respect to absolute dose accuracy for IMRT plans, percent depth dose accuracy for square fields between 2 and 20 cm, ability to measure composite plan isodoses and single beam fluence maps for IMRT cases, and sensitivity to processor variations over time. In 19 IMRT patient QA tests, the EDR2 film was able to achieve an absolute dose accuracy of better than 2% vs over 4% for XV2 film. The EDR2 film was able to reproduce ionization chamber and diode-measured percent depth doses to 20 cm depth generally to within 1% over the range of field sizes tested compared to about 10% for the XV2 film. When compared to calculations, EDR2 film agreed better than XV2 film for both composite plan isodoses and single beam fluence intensity maps. The EDR2 film was somewhat more resistant to processor changes over time than the XV2 film, with a standard deviation of dose reproducibility of less than 2% compared to 6%, respectively.

Equipment Failure Analysis↗

PubMed2005

Influence of phantom material and phantom size on radiographic film response in therapy photon beams.

The energy dependence of radiographic film can introduce dosimetric errors when evaluating photon beams. The variation of the film response, which is attributed to the changing photon spectrum with depth and field size, has been the subject of numerous publications in recent years. However, these data show large unexplained differences in the magnitude of this variation among independent studies. To try to resolve this inconsistency, this study assesses the dependence of radiographic film response on phantom material and phantom size using film measurements and Monte Carlo calculations. The relative dose measured with film exposed to 6 MV x rays in various phantoms (polystyrene, acrylic, Solid Water, and water; the lateral phantom dimensions vary from 25 to 50 cm square; backscatter thickness varies from 10 to 30 cm) is compared with ion chamber measurements in water. Ranges of field size (5 x 5 to 40 x 40 cm2) and depth (dmax to 20 cm) are studied. For similar phantom and beam configurations, Monte Carlo techniques generate photon fluence spectra from which the relative film response is known from an earlier study. Results from film response measurements agree with those derived from Monte Carlo calculations within 3%. For small fields (< or = 10 x 10 cm2) and shallow depths (< or = 10 cm) the film response variation is small, less than 4%, for all phantoms. However, for larger field sizes and depths, the phantom material and phantom size have a greater influence on the magnitude of the film response. The variation of film response, over the ranges of field sizes and depths studied, is 50% in polystyrene compared with 30% in water. Film responses in Solid Water and water phantoms are similar; acrylic is between water and polystyrene. In polystyrene the variation of film response for a 50 cm square phantom is nearly twice that observed in a 25 cm square phantom. This study shows that differences in the configuration of the phantoms used for film dosimetry can explain much of the inconsistency for film response reported in the literature.

Dose-Response Relationship, Radiation↗

PubMed2001

Stability of Liquid Films Containing Monodisperse Colloidal Particles.

Thin liquid films containing colloidal particles are considered to be the key structural elements of three-phase foams containing liquid, gas, and colloidal particles. This study is aimed at understanding the stability of such films in the absence of any surfactants. The particles form a layered structure in the film and produce a stepwise thinning in the thin liquid films. We report here for the first time the effects of particle concentration and size on film thickness transition of curved liquid films containing monodispersed colloidal particles. The rate of stepwise film thinning was observed to be high when particle concentration was low and both particle size and film size were large. The phenomenon of stepwise film thinning (i.e., stratification) is rationalized on the basis of diffusion of colloidal particles from the film to the meniscus, i.e., the diffusive osmotic mechanism. There exists a critical film size below which at least one layer of particles always stays in the film (i.e., black spot expansion does not occur). This critical size is dependent upon both particle size and concentration. Also, Monte Carlo simulations of the film show that, at a high particle concentration, better particle in-layer structure develops that increases the energy barrier, inhibiting particle diffusion from the film to the bulk meniscus. Copyright 2001 Academic Press.

Journal Article↗

PubMed2000

[Imaging of the microarchitecture and dynamics of the break-up phenomena of the preocular tear film with the aid of laser scanning microscopy].

BACKGROUND: Sufficient and regular wetting of the cornea with a normal preocular tear film is an essential requirement for the accurate visual functioning of the eye. Multiple factors may cause tear film instability. Measuring the break-up time of the preocular tear film is a necessary, clinically reliable means for evaluating tear film stability. We designed a new instrument to observe the preocular tear film at high magnification which can contribute to the in vivo imaging of the physiological and pathophysiological dynamics of the tear film and its break-up phenomena. MATERIALS AND METHODS: To image the tear film phenomena at sufficient magnification (x200) we used a confocal laser scanning microscope. Modification of an additional adaptor allows the tear film to be imaged at high magnification. This study evaluated the dynamics and microarchitecture of the break-up phenomena in the preocular tear film of normal patients and patients with "dry eye". RESULTS: Laser scanning microscopy allows high magnification imaging of the preocular tear film and evaluation of a number of break-up mechanisms. The dynamics and structure of the tear film was analyzed and documented. Based on our observations we formulate a new hypothesis on the break-up mechanism of the preocular tear film caused by alterations in the epithelial surface, for example, an elevation or tear film microparticle. By evaluating video sequences in the fluorescence and reflection modus of the laser scanning ophthalmoscope we also found early thinning of the aqueous layer simultaneously with an intact lipid layer covering the aqueous layer. CONCLUSION: Additional criteria result from using high-magnification microscopy, for example, laser scanning microscopy. This method reveals more microstructures of the corneal surface and the preocular tear film. The morphological representation of break-up phenomena leads to a better understanding of the underlying mechanisms and can be used for further investigations. Confocal laser scanning microscopy supplements the examination facilities and can be used in addition to slit lamp microscopy and to diagnose "dry eye".

Cornea↗

PubMed2005

Dexamethasone loaded bioresorbable films used in medical support devices: structure, degradation, crystallinity and drug release.

Bioresorbable polymer films containing dexamethasone (DM) were prepared using a solution processing technique. Investigation of the films focused on cumulative DM release as affected by film morphology (drug location/dispersion in the film) and degradation processes. Two film structures were studied: A-type, a polymer film with large drug crystals located on the film's surface, and B-type, a polymer film with small drug particles and crystals distributed within the bulk. The effect of the polymer's degree of crystallinity on the drug release profile was also studied. Prototypical applications of these films are biodegradable medical support devices which combine mechanical support with drug release. In most of our studied systems the drug release profile from the film is determined mainly by both drug location/dispersion in the film and the polymer's weight loss rate. All release profiles from A-type films exhibited a burst effect of approximately 30%, accompanied by a second release phase at a constant rate, whereas the release profiles from B-type films were determined mainly by the degradation profile of the host polymer, and did not exhibit any burst effect. A high degree of crystallinity is important for the current application, since good mechanical properties are required. This contributes to slower drug release rates, mainly at relatively low weight losses, whereas at high weight losses, where a porous structure is created, the crystallinity almost does not affect the rate of drug release. The shape of the porous structure that develops with degradation also affects the drug release profile from the B-type films.

Absorbable Implants↗