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PubMed1994

Electrophoretic mobility of salbutamol drug powder in mixed propellant solvents.

The influence of lipids on the dispersion properties of micronized Salbutamol base drug in liquid fluorocarbons has been characterized by electrophoretic mobility measurements and by particle size measurements. A modified Malvern ps26 microelectrophoretic cell was employed, allowing pressurized samples to be analyzed. The measurements were carried out at 25 degrees C in 100:0, 50:50, 40:60, and 30:70 blends of trichlorofluoromethane (P11) and dichlorodifluoromethane (P12) as a function of oleic acid concentration. A limited number of measurements were also done with soybean lecithin or synthetic dipalmitoylphosphatidylcholine (DPPC). A solvent series based on the polarizability (alpha) and on the dipole moment (mu) of the solvent molecules is constructed in order to estimate the acid-base character of the propellants. The results indicate that the type and the amount of lipids and also the type of fluorocarbon mixture plays an important role in the formation of surface charge. The dispersion stability with respect to the measured particle size does not always correlate with the measured electrophoretic mobility, and hence, the surface charge cannot alone explain the dispersion stability. Instead, the wettability of the powders seems to be important as well. Positive surface charge is obtained with the oleic acid or with synthetic dipalmitoylphosphatidylcholine, but negative surface charge exists with soybean lecithin.

Administration, Inhalation↗
PubMed2006

Surface engineering of microchannel walls for protein separation and directed microfluidic flow.

The preparation of surfaces in microfluidic devices that selectively retain proteins may be difficult to implement due to the incompatibility of derivatization methods with microdevice fabrication techniques. This review describes recently reported developments in simple and rapid methods for engineering the surface chemistries of microchannels based on construction of press-fit microdevices. These devices are fabricated by placing a glass fiber on a PDMS film and pressing the film on a silicon wafer or a microscope slide that has been derivatized with octadecyltrichlorosilane (ODS). The film adheres to the slide and forms an elliptically shaped channel around the fiber. The combination of surface wettability of a hydrophilic glass microfiber and the surrounding hydrophobic microchannel surfaces directs a narrow boundary layer of liquid next to the fiber in order to bring the sample in contact with the separation media and results in selective retention of proteins. This phenomenon may be exploited to enable microscale separation applications since there are a wide variety of fibers available with different chemistries. These may be used to rapidly fabricate microchannels that serve as stationary phases for separation at a microscale. The fundamental properties of such devices are discussed.

Electrophoresis, Microchip↗
PubMed1994

Medicinal applications of cyclodextrins.

Some cyclodextrins are produced industrially, and available in pharmaceutical quality, at reasonable prices. Their medicinal use means mainly--but not exclusively--the complexation of problematic drugs (poorly soluble, unstable, irritating, difficult to formulate substances). The CD complexation generally results in improved wettability, dissolution, and solubility; improved stability; reduced side effects; or in mildering of other undesired properties (e.g., bitter tastes, bad smells). CDs can be used advantageously practically in any drug forms: oral, rectal, pulmonary, external, ocular, etc. formulations. In oral solid and liquid formulations the chemical and physical stability and bioavailability, but particularly the role of absorption is improved. With appropriate highly soluble chemically modified CDs aqueous parenteral formulations can be prepared from poorly soluble drugs. Using CDs the transdermal penetration or nasal absorption of such drugs becomes possible, which earlier could not be administered through these ways. The direct therapeutic effects of CDs (or their derivatives) are demonstrated in several examples as well as the use of beta CD as vehicle in tabletting.

Chelating Agents↗
PubMed1992

Phospholipid composition and surface-active properties of tracheobronchial secretions from patients with cystic fibrosis and chronic obstructive pulmonary diseases.

Among the various components of tracheobronchial secretions, lipids and particularly phospholipids have been shown to influence rheological properties of airway secretions in patients with cystic fibrosis. We studied the phospholipid composition of tracheobronchial secretions, collected from patients suffering from cystic fibrosis (CF) and other chronic obstructive pulmonary diseases (COPD), and we analyzed the possible relationship between the phospholipid profile and the wettability of tracheobronchial secretions evaluated by the measurement of contact angle. Although total phospholipid content and contact angle of tracheobronchial secretions were significantly increased (P less than 0.01) in CF compared to COPD, no significant relationship existed between these two parameters. The concentrations of the different phospholipid subclasses were not homogeneously modified according to the origin of the secretions. Compared to COPD secretions, the CF secretions were characterized by a significant (P less than 0.001) increase in rigidifying fractions such as sphingomyelin and phosphatidylserine/phosphatidylinositol and a significant (P less than 0.001) decrease in surface-active fractions, such as phosphatidylcholine and phosphatidylglycerol (PG) (P less than 0.001). In the two groups, the surface-active phospholipid fraction, PG, was negatively correlated to the contact angle of tracheobronchial secretions. These results suggest that a decrease in PG content in CF secretions may be one factor responsible for an increase in their adhesivity to the respiratory mucosa, and, consequently, for mucus stasis and severity of bronchial obstruction in cystic fibrosis.

Adolescent↗
PubMed1992

Carboxylic acid-modified polyethylene: a novel support for the covalent immobilization of polypeptides for C-terminal sequencing.

We have developed a method for the covalent immobilization of peptides, for the purpose of C-terminal sequencing, to a novel solid support, carboxylic acid-modified polyethylene (PE-COOH) film. The peptides are attached by coupling the N-terminal amino group to the activated carboxyl groups of the film. Reagents for carboxyl group activation, including 1,3-dicyclohexylcarbodiimide (DCC), 1,1'-carbonyldiimidazole (CDI), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), benzotriazol-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP), and 1,3-diisopropylcarbodiimide (DICD) were compared. The best yields were obtained with DCC for a variety of tested peptides and averaged approximately 50%. The covalent attachment at pH 6.7 of peptides was shown to occur predominantly thorough the alpha-amino group for the peptide, SIGSLAK, which after attachment to the PE-COOH support permitted the C-terminal lysine residue to be sequenced in good yield, indicating that the epsilon-amino group of lysine is not covalently attached. This support offers a number of advantages over other solid supports, such as silica and polyvinylidene difluoride, for C-terminal sequencing including (1) stability to base and the high temperatures (65 degrees C) employed for C-terminal sequencing, (2) wettability with both aqueous and organic solvents, (3) a high capacity (1.6 nmol/mm2) for covalent coupling of polypeptides, and (4) easy divisibility into 1 x 5-mm pieces for use in our continuous flow reactor (CFR), which is also used for automated N-terminal sequencing (Shively, J.E., Miller, P., & Ronk, M., 1987, Anal. Biochem. 163, 517-529). Automated C-terminal sequencing on these supports is described in the companion paper (Bailey, J.M., Shenoy, N.R., Ronk, M., & Shively, J.E., 1992, Protein Sci. 1, 68-80).

Amino Acid Sequence↗
PubMed2004

Long-term selection for resistance to transgenic cotton expressing Bacillus thuringiensis toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).

Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hübner) were conducted using a leaf-feeding method with 42 selection episodes over 45 generations. The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F12) of selection. The survival rate of F12 neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R19 line were ca 34 and 72%, respectively, compared with ca 0 and 40% for a non-selected sister strain (NYCS), but lower than or similar to that of F12 feeding on leaves of non-Bt cotton, Sumian 12 (ca 87 or 76%). Resistance to B thuringiensis HD-1 Dipel in neonates (F12) was ca 6-fold. After 42 generations of selection, the strain developed a very high level of resistance to Cry1Ac protoxin, 210 g kg(-1) MVPII wettable powder and 200 g litre(-1) MVPII liquid formulation, the resistance ratios being 1680-, 1780- and ca 1200-fold, respectively, compared with a laboratory susceptible strain (HZS). When compared with the non-selected NYCS, the resistance ratios to the above toxins were ca 540-, 580- and 510-fold, respectively, but to Dipel only ca 16-fold. The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.

Animals↗
PubMed2003

Micro-electrospray with stainless steel emitters.

The physical processes underlying micro-electrospray (micro-ES) performance were investigated using a stainless steel (SS) emitter with a blunt tip. Sheathless micro-ES could be generated at a blunt SS tip without any tapering or sanding if ESI conditions were optimized. The Taylor cone was found to shrink around the inner diameter of the SS tubing, which permitted a low flow rate of 150 nL/min for sheathless microspray on the blunt tip (100 microm i.d. x 400 microm o.d.). It is believed that the wettability and/or hydrophobicity of SS tips are responsible for their micro-ES performance. The outlet orifice was further nipped to reduce the size of the spray cone and limit the flow rate to 50-150 nL/min, resulting in peptide detection down to attomole quantities consumed per spectrum. The SS emitter was also integrated into a polymethylmethacrylate microchip and demonstrated satisfactory performance in the analysis and identification of a myoglobin digest.

Gramicidin↗
PubMed2003

Electrospray ionization from a droplet deposited on a surface-modified glass rod.

This paper reports development of a non-mechanical electrospray ionization (ESI) method to generate electrospray from a droplet deposited on an optical fiber coated with a thin gold or Nafion film. Modification of the surface of the optical fiber in this manner increases its wettability, such that a droplet of the aqueous sample solution can adhere sufficiently strongly to the tip of the fiber. The aqueous sample solution was deposited near the tip of the fiber with a micropipette. When a high voltage (2,000 V) was applied to the fiber by electrical connection through the gold film, the sample solution moved and hung at the tip of the fiber. Simultaneously, ESI was generated from the sample droplet. Multiply charged peptide and protein ions were detected by connecting the ESI source to a quadrupole mass analyzer.

Angiotensin I↗
PubMedDate not supplied

Contact angle analysis on polymethylmethacrylate and commercial wax by using an environmental scanning electron microscope.

The environmental scanning electron microscope (ESEM) represents one of the most exciting breakthroughs in electron microscopy since the invention of the electron microscope. Its ability to observe uncoated and hydrated samples enhances the possibility for investigating the wettability of surfaces at a microscopic level; by varying the relative vapour pressure or the temperature inside the chamber, it is possible to condense water drops on a micron scale. A large problem in measuring contact angles by ESEM is that the observation angle is not parallel or perpendicular to the surface; thus, the study of the droplets profile using the common algorithms such as spherical approximation or axisymmetric drop shape analysis (ADSA) is not possible, because only a spherical cap shape is commonly observed. In this paper we provide a useful mathematical model to calculate the real contact angle from the initial images. Initially, some simulated spherical caps with different contact and observation angles were created by an appropriate graphic package in order to test the mathematical model. Some real drops obtained by ESEM on wax and polymethylmethacrylate (PMMA) were then studied and the results compared with contact angles measured by common methods on the same materials.

Journal Article↗
PubMed1994

Expanded fluorocarbon for keratoprosthesis cellular ingrowth and transparency.

The development of a synthetic material allowing increased cellular adhesion and ingrowth would improve keratoprosthetic devices and requires an understanding of cell colonization processes. Interlamellar implantation of hydrophobic synthetic material may lead to poor corneal nutrition with subsequent necrosis. The probability of necrosis increases with material which is more impermeable, larger in diameter and more anterior in its placement. In this study we demonstrated the importance of pore diameter in the rate and density of cell colonization. We demonstrated that an opaque hydrophobic material may become translucent and wettable with very low perturbation of flow through the cornea. We used an expanded polytetrafluoroethylene with either 20 microns or 50 microns pore diameter. Cellular ingrowth was significantly greater in the material with 50 microns pores, resulting in collagen deposition within the pores without corneal vascularization at 6 months follow-up. Immunohistochemical study with monoclonal antibody AE5 revealed normal epithelial differentiation on the surface of the cornea over the implanted polymer.

Animals↗
PubMed1997

Capillary Rise for Thermodynamic Characterization of Solid Particle Surface

Surface properties in terms of surface free energy of solid particles were investigated using capillary rise experimental methods based on Washburn's equation. Two different approaches related to height and weight gain measurements were validated by silica flour and calcium carbonate surface studies. Dispersive components of the surface free energy and nondispersive components of solid-liquid energy of interaction were computed. Some differences observed are related to experimental data acquisitions. Many experimental difficulties, which led in the past to inaccurate wettability characteristics, have been controlled. A new link to the so-called geometrical factor of Washburn's equation has also been established after comparison of theoretical and experimental static and hydrodynamic radii. The high precision of the weight gain approach was achieved by strict control of experimental parameters such as temperature, powder packing, and sintered glass porosity.

Journal Article↗
PubMed1997

A Film Tension Theory of Phagocytosis

A film tension criterion is derived on the basis of which it is possible to evaluate the probability of a particle or vesicle being phagocytosed by phagocytic cells. Variations of this criterion are arrived at by mechanical and thermodynamical analyses. Specific receptor-ligand binding interactions are included in the analysis, as are electrostatic, steric repulsive, and van der Waals attractive interactions between the surface of the phagocytosed particle and the pseudopods of the host cell membrane. Cytoskeletal forces proximate to the membrane are also implicitly included in the approach. The film tension criterion is shown to reduce to the classical wettability criterion in the limit of purely passive phagocytosis, wherein there are no electrostatic, steric repulsive, or receptor-ligand binding interactions between the cell and the phagocytosed particle. Several formulas characterizing various aspects of phagocytosis are derived. Opsonized particles are demonstrated to be more readily phagocytosed than nonopsonized particles, owing both to the energy of specific binding between opsonins and cell receptors and to the lowering of membrane tension that occurs in the vicinity of spreading pseudopods as a result of spontaneous actin polymerization. It is shown that certain particles or vesicles (those that are most easily phagocytosed) tend to be ingested more readily with increasing particle size, while others (those less easily phagocytosed) tend to be ingested more readily with decreasing size. In the limit of purely passive phagocytosis, formulas are developed for predicting the relative volumetric and particle-number uptake by cells as a function of organic/water partition coefficients. Partition coefficients of polystyrene particles and polymerized liposomes were measured and used to make theoretical predictions of particle uptake by macrophages. These predictions are compared with phagocytic uptake data for hydrophilic and hydrophobic nano- and microparticles. The comparisons show agreement between predicted trends of volumetric and particle-number uptake as a function of particle size, with uptake of hydrophilic nanoparticles diminishing with increasing size and uptake of hydrophobic nanoparticles increasing with increasing size (at least for submicrometer particles that are relatively insensitive to gravitational forces). Additional comparisons between published experimental data and theoretical predictions are also made. The potential use of the theory in characterizing the tendency of drug-loaded polymeric particles to be engulfed by macrophages is emphasized.

Journal Article↗
PubMed1997

ISS Assessment of the Influence of Nonpore Surface in the XPS Analysis of Oil-Producing Reservoir Rocks

The application of X-ray photoelectron spectroscopy (XPS) to oil-producing reservoir rocks is new and has shown that pore surface concentrations can be related to rock wettability. In the preparation of fresh fractures of rocks, however, some nonpore surface corresponding to the connection regions in the rocks is created and exposed to XPS. To assess the potential influence of this nonpore surface in the XPS analysis of rocks here we use ion scattering spectroscopy (ISS), which has a resolution comparable to the size of the pores, higher than that of XPS, with an ion gun of He+ at maximum focus. Sample charging effects are partially eliminated with a flood gun of low energy electrons. All the ISS signals are identified by means of a formula which corrects any residual charging on the samples. Three rock samples are analyzed by XPS and ISS. The almost unchanged ISS spectra obtained at different points of a given sample suggest that the nonpore surface created in the fracture process is negligibly small, indicating that XPS data, from a larger surface spot, represents the composition of true pore surfaces. The significant changes observed in ISS spectra from different samples indicate that ISS is sample specific. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Zeta Potential as a Tool to Characterize Plasma Oxidation of Carbon Fibers

Two different types of carbon fibers (ultrahigh modulus and high strength carbon fibers) were surface-treated in an oxygen plasma under equivalent conditions. Changes in the fiber surface chemistry were followed by electrokinetic measurements (zeta potential). The oxygen plasma treatment resulted in a displacement of the isoelectric point of carbon fibers toward lower pHs, evidence of an increase in the surface acidity. The possible simultaneous formation of basic functional groups was also inferred and supported by results obtained by inverse gas chromatography and wettability measurements. Differences were more evident with ultrahigh modulus carbon fibers than with high strength carbon fibers. It is concluded that the measurement of the electrokinetic properties constitutes a useful technique to follow the evolution of the surface chemical characteristics of different types of carbon fibers. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Interfacial Tension Measurement in DNAPL/Aqueous Surfactant Systems

Spinning drop tensiometry has been used in the past to determine low interfacial tension between aqueous surfactant solutions and organic phases that are lighter than water. In this work, we extend the use of the technique to measurement of low interfacial tension between aqueous surfactant solutions and organic phases that are denser than water by altering the wettability of the spinning glass tube. The interfacial tensions of water-SDS-PCE and water-SDS-TCE are determined using this new method. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Studies of Structure and Local Wetting Properties on Heterogeneous, Micropatterned Solid Surfaces by Microinterferometry.

The microstructure and the local wettability of functionalized patterns is reported. The patterns are formed by the photolithographic structuring of multilayers of hairy rod polymers on glass/MgF2/SiO2 substrates. By application of quantitative reflection interference contrast microscopy (RICM), the RICM image analysis was improved by accounting for (i) multiple reflections and the finite illumination aperture in stratified systems and (ii) geometrical effects in wedge-shaped systems and by (iii) optimizing the contrast enhancement through adjustment of the MgF2 coating. The surface free energy of hairy rod films were determined by analysing the contact angle of partially wetting liquid droplets as a function of the surface tension of the liquid. Periodic lattices of hydrophobic domains separated by hydrophilic domains were applied to check the theory of Joanny and de Gennes [J. Phys. Chem. 81, 552-562 (1984)] of contact angle hysteresis at periodic arrays of pinning centers. Measurements of the shape of the triple line and the contact angle hysteresis by RICM confirmed the theoretical predictions. Copyright 1997 Academic Press.

Journal Article↗
PubMed1998

Bubble Formation at Porous Hydrophobic Surfaces

The bubble formation properties of various porous surfaces at low gas supersaturations were investigated. Polystyrene and silica particles with pore sizes ranging from 40 to 1000 A were used as representative surfaces for this study. Among the polystyrene particles, those with the smallest pores generated the greatest numbers of bubbles at gas supersaturations of 5 and 15 atm N2. However, at supersaturations of 50 atm N2 all three polystyrene particles generated massive numbers of bubbles, obscuring any differences attributable to pore size. The surface wettability of the silica particles was altered by chemically coating the surfaces. Three of the four different silica particles initiated significantly greater numbers of gas bubbles after being coated with a hydrophobic silane layer. Hydrostatic prepressurization of the hydrophobic silica particles dramatically decreased the number of bubbles generated, suggesting that the bubble-initiating capability of these particles was due to gas trapped by the surfaces. In sharp contrast, the porous polystyrene particles showed no change in bubble nucleation capability following exposure to hydrostatic pretreatments of up to 1000 atm for 30 min. This suggests that gas not only may be trapped in the main pores of these particles, but also may be dispersed in undefined micropores throughout the polystyrene structure which may resist collapse by hydrostatic pretreatments of the magnitudes and/or durations used in this study. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1998

Interaction of Ionic Species and Fine Solids with a Low Energy Hydrophobic Surface from Contact Angle Measurement.

Interactions of ionic species, (organic and inorganic) precipitates, and fine solids with a low energy hydrophobic surface were examined using a model system of paraffin wax in aqueous solutions. Contact angle measurement was used to evaluate the interactions between paraffin wax and testing variables. No changes in contact angle were observed with various types of metal and metal hydroxyl ions, metal hydroxyl precipitates, fine silica, and alumina powders, suggesting weak or absence of interactions between these species and paraffin wax. At pH <9, the presence of amine reduced the contact angle, but no pH dependence on contact angle was observed for a given amine concentration. A sharp decrease in contact angle was observed at higher pHs, where precipitates of amine molecules formed probably on wax surfaces. In the presence of lauric acid, on the other hand, contact angles reduced at a pH below 8, due to the formation of precipitates, but the reduction was less significant, compared with the reduction by amine precipitates. At high pHs, adding lauric acid did not show any effect on the measured contact angles. The significant effect of fine solids on contact angle was observed only when the solids were made hydrophobic by adsorbed surfactants. The present study further demonstrated that both the thermodynamic criteria and the interactions among substrate/solids/surfactants/metal ions must be considered in identifying the effect of different factors on the wettability of low energy hydrophobic surfaces. Copyright 1998 Academic Press.

Journal Article↗