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PubMed2003

Evaluation of the film-forming property of hydrogenated rosin.

The film-forming and coating properties of a new biomaterial, hydrogenated rosin (HR), is investigated in the present communication. Films produced by casting method are studied for mechanical, (tensile strength, elongation, and Young's modulus), water vapor transmission, and moisture absorption characteristics. Type of plasticizer and its concentration were observed to play an important role in modifying the film characteristics. Dibutyl sebacate (DBS), a hydrophobic plasticizer, was found to be suitable for development of flexible and smooth films. Film formulations plasticized with DBS were investigated for coating the drug layered nonpareil seeds where plasticization facilitated development of smooth and uniformly coated pellets. The increase in coat buildup, however, did not sustain the drug release significantly. The studies conclude that HR films promise utility as moisture-protective hydrophobic, film-coating materials.

Absorption↗
PubMed2005

Development and evaluation of fast-dissolving film of salbutamol sulphate.

The objective of this work was to prepare and optimize the fast-dissolving film of salbutamol sulphate, which can be useful in an acute attack of asthma. The film was prepared using a solvent evaporation technique and is taken through the sublingual route. The film contains polyvinyl alcohol as a polymer, glycerol as a plasticizer, and mannitol as filler. A 33 full factorial design was utilized for the optimization of the effect of independent variables such as amount of polyvinyl alcohol, amount of glycerol, amount of mannitol on the mechanical properties, and % drug release of film. The multiple regression analysis of the results led to equations that adequately describe the influence of the independent variables on the selected responses. Polynomial regression equations and contour plots were used to relate the dependent and independent variables. The experimental results indicated that polymer concentration, plasticizer concentration, and filler concentration had complex effects on film mechanical behavior and % drug release. Furthermore, the desirability function was employed in order to determine the best batch out of all 27 batches of the factorial design. The % relative error was calculated, which showed that observed responses were in close agreement with the predicted values calculated from the generated regression equations. It was found that the optimum values of the responses for fast release film could be obtained at medium levels of polyvinyl alcohol and glycerol, and a high level of mannitol. The prepared film was clear, transparent, and had a smooth surface. The concept of similarity factors Sd was used to prove similarity of dissolution between distilled water and simulated saliva (pH 6.8) or simulated gastric fluid (pH 1.2).

Albuterol↗
PubMed2004

Complexation between PVP and Gantrez polymer and its effect on release and bioadhesive properties of the composite PVP/Gantrez films.

Complexation between poly(methyl vinyl ether-maleic anhydride) copolymer (Gantrez AN 169) and polyvinylpyrrolidone (PVP K-90D) in aqueous solutions were investigated using a viscometric method and Raman spectroscopy. The composite films with different weight ratios of PVP to Gantrez were prepared in the presence of N-methyl-2-pyrrolidone. The release profiles of diclofenac sodium (DS) from these films were determined and the bioadhesive properties measured. An interpolymer complex was formed through hydrogen bonding between the carbonyl groups of PVP and the hydroxyl groups of Gantrez. The formation of interpolymer hydrogen bonds reduced the interaction of the polymers with water molecules, thus resulting in a lower solubility of the complex in water and a further retarded release of DS from the composite films. The interpolymer complexation was also found to increase the bioadhesive properties of the composite films to a silicone elastomer substrate. The complexation of PVP and the Gantrez copolymer in the composite films was a critical factor affecting the release of DS from the films and the bioadhesive properties of the films.

Adhesives↗
PubMed1980

Proton transport by bacteriorhodopsin in planar membranes assembled from air-water interface films.

Bacteriorhodopsin, in known amounts and controlled orientation, is incorporated into planar membrane films. These films are formed by the sequential transfer of two air-water interface films onto a thin, hydrophilic, electrically conductive support cast from nitrocellulose. The films are easily accessible to electrical measurements and to control of the ionic milieu on either side of the membrane. The area of the assembled membrane films can be varied between 2.3 x 10(-2) cm2 and 0.7 cm2. Illumination of these films produces photocurrents, photovoltages, and changes in the pH of the surrounding medium. The peak amplitude of the photocurrent increases linearly with light intensity for dim lights, and it approaches a saturating value for brighter lights. In the linear range, the stoichiometry of transport is 0.65 +/- 0.06 protons/absorbed photon. The rate of transport is linearly proportional to light at all intensities tested. The amplitude and kinetics of the photovoltage measured are accurately predicted by the photocurrent generated and the passive electrical features of the film. Parallel measurements of pH and photocurrent reveal that the light-induced changes in pH are fully accounted for by the rate and amount of charge transport across the membrane. Preceding the transport of protons, a transient photovoltage is detected that exhibits no detectable latency, reaches peak in about 80 microseconds, and probably arises from light-induced intramolecular charge displacements.

Air↗
PubMed2005

Physicochemical properties and in vivo assessment of timolol-loaded poly(D,L-lactide-co-glycolide) films for long-term intraocular pressure lowering effects.

Timolol-loaded poly(D,L-lactide-co-glycolide; PLGA) films were prepared for achieving the long-term intraocular pressure (IOP) lowering effect on glaucoma treatment. The physicochemical properties and in vivo effects of films were determined and characterize the delivery system. PLGA, span 20, propylene glycol (PG), and timolol base were dissolved in dichloromethane (DCM) and kept in a stainless mold; timolol films were prepared after the evaporation of DCM. Timolol disc-shape film preparation (TDF), containing 1 mg of timolol in 0.37 cm(2) area, was fabricated by using a trephine and placed onto the cul de sac of alpha-chymotrypsin-induced ocular hypertension rabbits for assessing the IOP lowering effect. The prepared films characterized a Young's modulus ranged from 1.13 to approximately 2.49 MPa, and related to the content percentages of PLGA, PG, and the residual DCM. The timolol film could maintain drug release for 1 week. Following a single-dose application in ocular hypertension rabbits, the prepared TDF could achieve a long-term IOP lowering effect and maintain the IOP change (in comparison with baseline) of approximately 7 mmHg within 1 week. The aqueous humor levels of timolol were low within a range of 0.8 to approximately 0.24 microg/mL for the initial 24 h and less than 0.15 microg/mL for 4-7 days. The investigated film formulation might be potentially developed for the application of long-term ocular delivery systems.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Thermoresponsive terpolymeric films applicable for osteoblastic cell growth and noninvasive cell sheet harvesting.

A novel multifunctional linear block copolymer, poly(N-isopropylacrylamide-co-acrylic acid)-b-poly( L-lactic acid) (NAL), was synthesized to expand the concept of cell sheet engineering by using its thermoresponsive property and processibility. The chemical structure of synthesized NAL was confirmed by Fourier transform infrared spectroscopy, and its molar mass (103,500 g.mol(-1)) and molar mass distribution were determined by matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. NAL copolymer was fabricated into thin films by spin-casting. Spin-cast NAL films displayed thermoresponsive properties as demonstrated by surface wettability and topology changes from relatively more hydrophobic (contact angle of 56 degrees) and rougher at 37 degrees C to relatively more hydrophilic (contact angle of 40 degrees) and smoother at 22 degrees C, as assessed by contact angle measurement and atomic force microscopy, respectively. Murine osteoblastic MC3T3-E1 cells displayed comparable adhesion but slower proliferation on NAL films than on poly(L-lactic acid) (PLLA) films and tissue culture polystyrene (TCPS). Within 9 days of cell culture, the highest alkaline phosphatase activity of MC3T3-E1 cells occurred later (on day 9) on NAL films than on PLLA films and TCPS (on day 6). A well-established MC3T3-E1 cell sheet was successfully detached from NAL films, in the absence of enzymes, within about 5 min by simply lowering the temperature from 37 degrees C to room temperature. NAL copolymer has potential for use in the controlled release of therapeutic agents while simultaneously supporting cell growth. In addition, it may be applicable for noninvasive two- or three-dimensional cell sheet harvesting.

Alkaline Phosphatase↗
PubMed2004

Development of a rabbit model of tear film instability and evaluation of viscosity of artificial tear preparations.

OBJECTIVE: The purposes of this study were to establish a quantitative method for evaluating rabbit tear film status and investigate the efficacy of artificial tear preparations through ocular surface bathing or eye drop application. METHODS: The rabbit tear film was evaluated using a noninvasive specular reflection video recording system. The appearance of a tear break area (TBA) on the tear film images (7.4 mm2/mm) after 30 seconds of eye opening was quantified by image analysis. To induce disruption of the rabbit tear film, the ocular surface was challenged for 60 minutes with 1 ppm hypochloric acid (HOCl). Immediately after irrigation, artificial tear preparations composed of viscosity agents sodium hyaluronate (SH), hydroxypropylmethycellulose (HPMC), hydroxyethylcellulose (HEC), or chondroitin sulfate (CS) were applied to the rabbit eye through ocular surface bathing or eye drop application, and the recovery of the disrupted tear film was compared for each preparation. RESULTS: A dramatic increase in TBA was observed immediately after the ocular surface was challenged with HOCl, and it returned to the initial level after 6 hours. Immediately after ocular surface bathing and eye drop application, a dramatic recovery of TBA was observed in all the test solution-treated eyes. One hour after treatments, prolonged amelioration of the tear film instability was observed after ocular surface bathing, but not by eye drop application, with the artificial tear preparations composed of HPMC or SH. CONCLUSION: Ocular surface bathing with artificial tear preparations composed of a suitable viscosity agents could be useful in managing tear film instability.

Animals↗
PubMed2001

Prospective comparison of admission computed tomographic scan and plain films of the upper cervical spine in trauma patients with altered mental status.

OBJECTIVE: The accurate evaluation of patients with multiple injuries is logistically complex and time sensitive, and must be cost-effective. We hypothesize that computed tomographic (CT) scan of the upper cervical spine (occiput to C3 [Co-C3]) would add little to the initial evaluation of patients with multiple injuries who have altered mental status. METHODS: The study consisted of a prospective, unblinded, consecutive series. Patients met entry criteria if they had sustained a blunt mechanism of injury and had an altered mental status requiring CT scan of two or more body systems. All patients received CT scan of Co-C3 with 2-mm cuts and subsequent reconstructions as well as five-view cervical spine plain films. Cervical spine injury was defined as any radiographically identified fracture or subluxation that required treatment. Patients were excluded if they died or were cleared clinically before plain film series were obtained. CT scan of Co-C3 and cervical spine films were reviewed by two different attending radiologists. RESULTS: Of the 2,690 consecutive admissions between December 1998 and November 1999, 1,356 patients met entry criteria. Seventy patients (5.2%) had a total of 95 injuries to the upper cervical spine. CT scan of Co-C3 identified 67 of 70 patients and plain films identified 38 of 70 patients with injuries to the upper cervical spine. Twelve patients (17%) had neurologic deficits attributable to Co-C3 injuries. Three patients had false-negative CT scans of Co-C3, and one patient was quadriplegic. There were 32 patients with false-negative plain films, including four patients with motor deficits (one with quadriplegia). Use of the guidelines developed by the Eastern Association for the Surgery of Trauma identified all patients with upper cervical spine injuries; to date, no patient in the study group was readmitted or has initiated a lawsuit for missed injury of the upper cervical spine. CONCLUSION: CT scan of Co-C3 was superior to plain films in the early identification of upper cervical spine injury. Plain films failed to identify 45% of upper cervical spine injuries; four of these missed injuries resulted in motor deficits. Our study supports the practice guidelines developed by the Eastern Association for the Surgery of Trauma for clearance of the upper cervical spine in patients with altered mental status, as all patients with injuries were identified using these guidelines.

Adolescent↗
PubMed2002

Lumbar fractures in adult blunt trauma: axial and single-slice helical abdominal and pelvic computed tomographic scans versus portable plain films.

BACKGROUND: Our hypothesis was that abdominal and pelvic computed tomographic (AP-CT) scans are equivalent to portable two-view plain films in detecting lumbar spine fractures in adults. Since many trauma patients often undergo AP-CT scanning to evaluate for possible intra-abdominal injuries, using the AP-CT scan to screen for lumbar fractures could make the trauma evaluation process more efficient. METHODS: The institutional trauma registry at a Level I trauma center was used to identify all blunt lumbar fractures during a 6-year period. Medical records were reviewed. RESULTS: A total of 7,216 adult blunt trauma patients were evaluated, and 115 patients were identified as having a lumbar fracture, for an incidence rate of 1.6%. Missed fracture rates were high for both AP-CT scans (23.2%, 13 of 56) and portable two-view films (12.7%, 14 of 110, = 0.08). Fifty-two patients had both AP-CT scans and plain films. In this group, AP-CT scans missed 23.1% (12 of 52) of the lumbar fractures and plain films missed 15.4% (8 of 52). However, the combination of the two diagnostic methods did not miss any fractures (0 of 52). The missed fractures required surgery or brace in 50% (7 of 14) patients who had fractures missed by plain films and 46% (6 of 13) patients whose fractures were missed by AP-CT scanning. CONCLUSION: Both AP-CT scans and plain films failed to diagnose significant lumbar fractures that required therapy. When screening for lumbar fractures, obtaining both AP-CT scans and portable two-view plain films may decrease missed lumbar fractures in blunt adult trauma.

Adult↗
PubMed1996

Lens adherence and postlens tear film changes in closed-eye wear of hydrogel lenses.

BACKGROUND: Lens adherence and a reduced postlens tear film circulation have been suggested as factors contributing to some adverse reactions in extended wear of hydrogel contact lenses. In this study, we determined lens fitting and postlens tear film characteristics during closed-eye wear. METHODS: Twenty subjects wore hydrogel lenses for 3 h of eye closure, followed by 30 min of open-eye wear. Lens movement was measured with a video biomicroscope. Postlens tear film appearances in specular reflection were classified as either amorphous, or as one of four color intensity grades, where a colored appearance was taken as indicative of a depleted postlens tear film. RESULTS: All subjects showed lens adherence (movement < 0.1 mm) and postlens tear film depletion within 45 min of eye closure. These changes were sustained for the remainder of the closed-eye period, but were reversed within 15 min of eye opening. Lens adherence was associated with colored postlens tear film patterns of any intensity. CONCLUSION: Closed-eye wear was invariably associated with the onset of lens adherence and postlens tear film depletion. This finding emphasizes the need for adequate lens movement during the open-eye phase of extended wear.

Adhesiveness↗
PubMed2006

Tear film lipid layer alterations in allergic conjunctivitis.

PURPOSE: To assess the alterations of the tear film lipid layer and tear functions in patients with seasonal allergic conjunctivitis (SAC) and to compare the results with healthy control subjects. METHODS: Seventy-eight eyes of 39 consecutive patients diagnosed as SAC (mean age 32.6 years; 11 male, 28 female) as well as 20 eyes of 10 healthy control subjects (mean age 32.5 years; 6 male, 4 female) underwent slit-lamp examinations, tear film breakup time measurements (BUT), corneal fluorescein stain scoring, Schirmer test, and tear film lipid layer interferometry. The 2 groups were then compared for the examined parameters. RAST and serum IgE level evaluations were also carried out in the patients to confirm the diagnosis of allergy. RESULTS: The mean BUT was 3.4 +/- 1.5 seconds in patients with SAC compared with the mean value of 12.4 +/- 2.4 seconds in the controls (P < 0.05). There were no significant differences in relation to Schirmer test values between the 2 groups; 78% of the patients with SAC had grade 3 or above dry eye change in tear film lipid layer interferometry, whereas none of the controls had an interferometry grade greater than 3 (grade 1-2 normal; grade 3-4 dry eye; grade 5 severe dry eye). Eyes with SAC had significantly higher tear film lipid layer thickness ranges compared with the control eyes (P < 0.05). CONCLUSION: SAC was associated with advanced tear instability and thickening of the tear film lipid layer. Evaluation of the tear film lipid layer thickness might be useful in the assessment of the extent of dry eye disease and the treatment outcomes in patients with allergy.

Adult↗
PubMed1999

Vertical free-standing films of amphiphilic associating polyelectrolytes.

Hydrophobically modified poly(acrylic acid) sodium salt (HMPAANa) copolymers are known to provide a huge stabilization of oil in water macroemulsions. An interstitial HMPAANa film is formed between the oil droplets, thus creating repulsion between them. We present an x-ray reflectivity study of vertical free-standing films drawn from aqueous solutions of HMPAANa copolymers. The vertical HMPAANa films are model systems for the interstitial films between oil droplets and the description of their behavior provides information about the stabilization process. Their thickness was investigated as a function of various parameters such as the solution concentration, the degree of grafting, the length of the grafts, and the backbone molecular weight. Below a solution concentration threshold (C(t)), the film thickness scales like the square root of the molecular weight and is independent of the degree of grafting and the length of the grafts. Polyelectrolyte chains adopt a self-screened coil conformation within the films and the thickness is governed by the radius of gyration of the coils. Above C(t), a transition from a bimolecular film to a physical gel is observed and the thickness then increases with concentration. Finally, we propose an explanation for the stabilization of macroemulsions by HMPAANa copolymers.

Journal Article↗
PubMed2000

Molecular mobility in polymer thin films

Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T(g), and in the range of film thicknesses from 1-10(2) times the radius of gyration (R(g)) of individual polymer molecules. As the film thickness decreases towards R(g) the value of D increases above the bulk values, with significant effects first appearing in films approximately 20R(g). In the thinnest films studied, about 4R(g), the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T(g) and the thermal expansion coefficient for liquid state, alpha(L), decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed.

Journal Article↗
PubMed2002

Dynamic and correlation properties of solid supported smectic-A films.

Dynamic properties and layer displacement-layer displacement correlation functions of the smectic-A films on a substrate are investigated. The eigenfrequencies spectrum and eigenmotions of the film are calculated within the framework of a discrete model. It was found that the static as well as dynamic properties of freely standing and solid supported smectic-A films differ significantly. In particular, the acoustic mode is absent in the films on a substrate and the surface tension is not essential for the film dynamics. The correlation length of the spatial layer displacement correlation functions is finite for films on a substrate in contrast to the free standing films. An effect of thermal fluctuations on the specular and diffuse x-ray scattering was analyzed.

Journal Article↗
PubMed2003

Molecular arrangements of self-assembled surfactant films: characterization from atomic force microscopy data.

The adsorbed surfactant film molecular arrangement with thickness of approximately 5 nm is determined by measurements of the film dielectric permittivity. Before the advent of atomic force microscopy the dielectric permittivity was a macroscopic parameter, appropriate only for describing uniform environments since its profile was difficult to measure for local intermolecular interactions and its spatial distribution was frequently settled without experimental justification. Here, we show that atomic force microscopy made it possible to measure the dielectric permittivity profile in a scale below 5 nm for adsorbed layers of self-assembled surfactant films in water. The measured values of the film's dielectric permittivity and the film's thickness determine the compactness of the adsorbed film and consequently the presence of water molecules in the film and the conformal structure of the adsorbed molecules.

Journal Article↗
PubMed2003

Weak nonlinear surface-charging effects in electrolytic films.

A simple model of soap films with nonionic surfactants stabilized by added electrolyte is studied. The model exhibits charge regularization due to the incorporation of a physical mechanism responsible for the formation of a surface charge. We use a Gaussian field theory in the film but the full nonlinear surface terms which are then treated at a one-loop level by calculating the mean-field Poisson-Boltzmann solution and then the fluctuations about this solution. We carefully analyze the renormalization of the theory and apply it to a triple-layer model for a thin film with Stern layer of thickness h. For this model we give expressions for the surface charge sigma(L) and the disjoining pressure P(d)(L) and show their dependence on the parameters. The influence of image charges naturally arises in the formalism, and we show that predictions depend strongly on h because of their effects. In particular, we show that the surface charge vanishes as the film thickness L-->0. The fluctuation terms in this class of theories contribute a Casimir-like attraction across the film. Although this attraction is well known to be negligible compared with the mean-field component for model electrolytic films with no surface-charge regulation, in the model studied here these fluctuations also affect the surface-charge regulation leading to a fluctuation component in the disjoining pressure which has the same behavior as the mean-field component even for large film thickness.

Journal Article↗
PubMed2006

Breath figure templated self-assembly of porous diblock copolymer films.

Porous polyethylene oxide-b-polyfluorooctylmethacrylate (PEO-b-PFOMA) diblock copolymer films were drop cast onto substrates from Freon (1,1,2-trichlorotrifluoroethane) in a humid atmosphere. The pores in the films exhibit long range hexagonal order in some cases, depending on the PFOMA-to-PEO molecular weight ratio. Films with the best ordered pores were formed with PFOMA-to-PEO ratios of 70 kDa:2 kDa. The pores in the polymer films derive from water droplets that condense as Freon evaporates. The polymer stabilizes the water droplets, or "breath figures," which act as an immiscible template that molds the porous film. Increased polymer hydrophobicity reduces the water wettability of the air/Freon interface, which in turn decreases water droplet nucleation, thus influencing the final pore size and spatial order in the polymer films. We describe how water droplet nucleation influences the final pore size and packing order in the polymer films.

Journal Article↗
PubMed2006

Measurement of the viscosity coefficient eta3 in free-standing smectic films.

Thinner parts (the so-called holes) and thicker parts (islands) move in free-standing smectic films due to gravity if the film is inclined. The velocity of the movement depends on the viscosity coefficient eta3 of the film. Therefore, this measurement is a direct method to determine eta3 in smectic phases. This paper contains the corresponding hydrodynamic calculations for the flow patterns in and around a circular hole in a circular two-dimensional film under various conditions. The viscous force on the hole is calculated. Experiments are performed with the liquid crystal n-octyl-cyano-biphenyl (8CB) in the smectic phase. The influence of the disclination which surrounds the hole and the influence of the gas which surrounds the film on the movement is studied. It is shown that the influence of these effects on the determination of eta3 can be neglected if the film is thick and the difference in the thicknesses between film and hole is small. The temperature dependence of eta3 is determined for 8CB.

Journal Article↗