Emulsified Oil Droplets Research Articles

Crystallization in oil-in-water emulsions containing liquid and solid droplets

The kinetics of crystallization of supercooled oil droplets in emulsions containing a mixture of solid and liquid n-hexadecane droplets has been monitored at constant temperature from time-dependent measurements of the velocity of ultrasound. In emulsions stabilized by non-ionic surfactant (Tween 20 or C 12E 8) or anionic surfactant (sodium dodecyl sulphate, SDS), crystallization is induced in liquid droplets when solid droplets are present; in the absence of solid droplets crystallization proceeds at a negligible rate. Increasing the aqueous phase surfactant concentration leads to a substantial increase in the crystallization rate in Tween 20 emulsions. Ionic strength has no significant effect on the rate in SDS emulsions. The mechanism of this crystallization probably involves crystals on solid droplets penetrating into supercooled liquid droplets during collisions and thereby acting as nucleation sites for crystal growth. The process is enhanced by aggregated surfactant molecules bridging between the colliding droplets.

Solids-stabilized oil-in-water emulsions: Scavenging of emulsion droplets by fresh oil addition

A novel method for breaking up solids-stabilized oil-in-water emulsions was investigated on the basis of a simple concept. Kaolinite clay particles were used as the stabilizing solids, whose wettability (contact angle) was varied by controlling the amount of asphaltene adsorption on the clay particles. A light mineral oil (Bayol-35) was used as the dispersed phase. It was found that the contact angle of the treated clay particles, measured across the water phase, increased with increasing asphaltene concentration. The prepared emulsion (oil) droplet size increased significantly with increasing clay contact angle. The demulsification process was conducted in a 1 1 beaker equipped with baffles, under stirring action. The method of scavenging emulsion oil droplets by the use of large fresh oil droplets proved to be effective. The demulsification was enhanced with increasing amount of fresh oil added. The demulsification was more effective for emulsions stabilized with clays having larger contact angles. An increase in the rotational speed of the stirrer also enhanced the demulsification process.

Positively charged submicron emulsions — a new type of colloidal drug carrier

A positively charged submicron emulsion was prepared and stabilized by forming a mixed film comprising phospholipids, poloxamer and stearylamine at the o/w interface of the oil droplets. This was confirmed concomitantly by the selective adsorption of the thiocyanate anion and the lack of adsorption of Ca 2+ onto the emulsified oil droplets of the actual emulsions. The incorporation of various drugs in the new type of submicron emulsions altered neither the nature of the surface charge nor the mean droplet size. These results clearly demonstrated that the positively charged submicron emulsion can be used as a new type of colloidal drug carrier.

Size Control of Ibuprofen Microspheres with an Acrylic Polymer by Changing the pH in an Aqueous Dispersion Medium and Its Mechanism.

The size of ibuprofen microspheres fabricated by the o/w emulsion solvent diffusion method was controlled by adjusting the pH (1.0-5.0) in an aqueous dispersion phase. As the pH decreased, the diameter of the microspheres decreased, while drug entrapment efficiency and yield of microspheres remained unchanged. In the present system, the size of microspheres increased via coalescence and fusion of the oil emulsion droplets before solidification of the droplets occurred. At a lower pH, the solvent (ethanol) diffiusion rate from the oil droplets to the squeous phase was accelerated, and the drug and polymer solved in the oil droplets were rapidly deposited, forming a rigid outer-shell on the surface of the droplets to prevent the coalescence and fusion. These accelerations of solvent diffusion and rapid solidification were attributed to that the hydrogen bonding between drug and solvent, and the solubility of drug in the droplets were reduced in the strongly acidic (low pH) aqueous medium.

The cell biology of proliferative disorders at the vitreo-retinal interface

Large relaxing retinectomies have become increasingly used in the repair of retinal detachment related to proliferative vitreoretinopathy (PVR). Retinectomies expose the retinal pigment epithelium (RPE) to the vitreous cavity; the direct effects of silicone oil on the RPE are only beginning to be understood.Retrospective case series.Twelve patients noted to develop pigmented epiretinal deposits at regularly scheduled follow-up visits after repair of complex retinal detachments using silicone oil tamponade and retinectomy.Epiretinal pigment deposits were characterized clinically by wide-field color photography, fundus autofluorescence imaging, and spectral-domain optical coherence tomography (SD OCT). At the time of silicone oil removal, the pigmented membranes were preserved in fixative and analyzed by light microscopy/immunostaining or electron microscopy for histologic characterization.Not applicable.We describe the development of diffuse preretinal pigmentary deposits in 12 eyes after surgery for complicated PVR detachments using retinectomies with oil, with an average onset of 3.2 months postoperatively. These pigment clumps produced a striking leopard-spot pattern on fundus autofluorescence imaging. Histopathologic and ultrastructural analysis of these epiretinal proliferations peeled at the time of silicone oil removal revealed RPE cells with intracellular silicone oil droplets, singly dispersed membrane-bound melanin granules, glial tissue (1 case), and a fibrous stroma.Although in vitro studies have suggested that RPE cells can phagocytose emulsified oil droplets, this report represents the first in vivo documentation by electron microscopy of this phenomenon in patients. These findings underscore that direct contact with silicone oil may affect the behavior of the RPE, which may be clinically relevant in patients who have undergone large relaxing retinectomies with silicone oil tamponade for PVR-related retinal detachments.

Comparisons of pinhole and linearly collimated SAXS and SANS study of emulsified oil droplets

The same samples, large emulsified oil droplets (1000Å to 1 μm) have been studied by SANS using pinhole collimation (D11 at ILL) and also linear collimation using a double crystal spectrometer (S21 at ILL). We tested the deconvolution procedure based on two very different principles: one described by Lake and the other one proposed by Strobl for the X-ray Kratky camera. The sample structure has also been studied with an ultra SAXS triple axis Bonse-Hart camera. We compare results obtained by these three different experimental methods.

The influence of minor surface-active components of olive oil on emulsification with bovine serum albumin

Minor surface-active lipids occurring in virgin olive oil enhance the interfacial area per millilitre of oil created during the emulsification by bovine serum albumin (BSA). These components adsorb at the newly formed oil—water interface, bring about a marked decrease in the interfacial tension value and aid, together with adsorbed protein molecules, in the formation and stabilization of emulsion oil droplets. Minor surface-active lipids do not appear to affect the amount of protein adsorbed at the oil—water interface. This could mean that the penetration of the interface by protein molecules arriving at the interface is not inhibited by the presence of already adsorbed surface-active lipid molecules.

Emulsifying Properties of a Mixture of Peptides Derived from the Enzymatic Hydrolyzates of Bovine Caseins

β-CN(f193–209), a hydrophobic peptide of 17 residues obtained from the chymosin hydrolyzate of β-casein, had little emulsifying activity (EA) at a neutral pH. When mixed with a hydrophilic glycomacropeptide (GMP) derived from κ-casein however, the EA of β-CN(f193-209) increased greatly. The mixing ratio of the peptides affected the EA as well as the adsorption of the peptides to oil droplets. Scanning electron microscopy indicated that the peptide film surrounding the emulsified oil droplets was thick and rough compared to the protein film. An amphipathic structure formed by some interaction between the hydrophilic GMP and the hydrophobic β-CN(f193-209) might contribute to the formation of the thick peptide film and stabilize the emulsified oil.

Emulsifying properties of a mixture of peptides derived from the enzymatic hydrolyzates of bovine caseins.

β-CN(f193–209), a hydrophobic peptide of 17 residues obtained from the chymosin hydrolyzate of β-casein, had little emulsifying activity (EA) at a neutral pH. When mixed with a hydrophilic glycomacropeptide (GMP) derived from κ-casein however, the EA of β-CN(f193-209) increased greatly. The mixing ratio of the peptides affected the EA as well as the adsorption of the peptides to oil droplets. Scanning electron microscopy indicated that the peptide film surrounding the emulsified oil droplets was thick and rough compared to the protein film. An amphipathic structure formed by some interaction between the hydrophilic GMP and the hydrophobic β-CN(f193-209) might contribute to the formation of the thick peptide film and stabilize the emulsified oil.

MICROCRYSTALLINE CELLULOSE STABILIZEDEMULSIONS

ABSTRACT Miorocrystalline cellulose stabilized emulsions (o/w) were evaluated by means of brightfield and polarized light microscopy, freeze-etch electron microscopy, droplet size analyses and rheologic measurements. These studies indicated that miorocrystalline cellulose (Avicel RC591 ) forms a network around emulsified oil droplets. This structure provides a mechanical barrier at the o/w interface which stabilizes the emulsion without the necessity for decreasing interfacial tension, as in conventional surfactant-stabilized emulsions. Rheologic studies indicated that emulsions containing Avicel RC591 had a considerable degree of thlxotropy which contributed to their stability. When Tween 80 was incorporated in this system, oil droplets coalesced indicating that the stability of the emulsion was affected adversely.

An adsorption effect on the gel strength of dilute gelatin-stabilized oil-in-water emulsions

The incorporation of emulsion oil droplets into a gelatin gel leads to an initial increase in shear modulus at 25 °C for a gelatin concentration of 8 wt % but an initialdecrease for a concentration of 5 wt %. The latter result is consistent with a net lowering of the gelatin concentration available for gelation in the aqueous phase due to adsorption at the oil-water interface.

Phagocytosis, Chemiluminescence, and Cell Volume of Alveolar Macrophages From Neonatal and Adult Pigs

Broncho-alveolar cells lavaged from the lungs of 1- and 7-day-old piglets and adult pigs were examined to determine their alveolar macrophage content, cell size, and ability to phagocytyze emulsified oil droplets and to chemiluminesce in response to opsonized zymosan particles. Alveolar macrophages were identified by specific cytochemical stains and differential cell counts as being 95%, 97%, and 90% of the cell populations, respectively. The cell volume of macrophages from 1-day-old pigs was 383 +/- 40 microns3; while the cell volumes from 7 day and adult pigs were 1,660 +/- 265 and 1,411 +/- 310 microns3. Alveolar macrophage from 1-day-old piglets possessed little ability to engulf oil droplets; however, macrophages from 7-day-old piglets phagocytized these opsonized droplets at a rate equivalent to alveolar macrophages obtained from adult pigs. The phagocytosis of oil droplets by both 7-day and adult alveolar macrophages manifested similar characteristics. Both rates can be described by saturation kinetics, and while temperatures from 37 degrees to 30 degrees C had little effect, the rate declined rapidly between 30 degrees and 16 degrees C. Alveolar macrophages from 1-day-old piglets displayed a lower magnitude of chemiluminescence than cells from 7-day-old and adult pigs and did not always respond to zymosan exposure. On the other hand, 7-day-old and adult pig alveolar macrophages were quite similar in their ability to chemiluminesce. Increasing extracellular glucose from 1 to 20 mM induced a concomitant increase in chemiluminescence. The findings suggest that functionally competent alveolar macrophages emerge in the pig lung approximately 1 week after birth.

Internal Phase Size Effects on Combustion of Emulsions

Abstract Abslract –The combustion of isolated, free and suspended droplets of a residual oil-water emulsion nas been studied. A constant water content of 5 percent by volume was used but the size distribution of the internal water-phase particles was varied. It was found that the intensity of the disruptive phenomenon was sensitive to the size of the water particles in the emulsion. Emulsified oil droplets with a mean water particle diameter of 2. 1 microns exhibited weak disruptive activity which had no effect on the size of the coke particles subsequently formed. However, when the mean water particle size was increased to 4.5 microns, disruption of the droplet was intense and the very small coke particles formed from the fragments of the shattered droplet quickly burned out. The results indicate that attention should be given to the emulsion structure in evaluating the effectiveness of oil-water emulsions in reducing coke particulates in boilers.

Induction of resistance to tuberculosis in mice with defined components of mycobacteria and with some unrelated materials

Factors contributing to protection against experimental tuberculosis have been studied with refined and well-characterized fractions from mycobacteria and with certain unrelated antigens. Mice were vaccinated intravenously with various combinations of materials presented on minute oil droplets in saline emulsion and were later challenged by aerosol. The minimal composition of an effective vaccine was P3 (a trehalose mycolate similar to cord factor) plus an antigen, which could be tuberculo-protein, or a low-molecular-weight tuberculin-active peptide, or unrelated antigen such as bovine serum albumin or bacterial endotoxin. Development of a hypersensitivity granuloma in the lungs appeared to be essential to protection in this laboratory model.

Regression of tumors by an endotoxin combined with trehalose mycolates of differing structure

A transplantable hepatocarcinoma of guinea pigs has been used as a model for study of immunotherapy of malignant tumors. Cures of established neoplasms have been effected with viable bacillus Calmette-Guerin (BCG); and certain microbial fractions, when presented in association with oil droplets in saline emulsion, have also caused regression of the tumors. P3, a mycobacterial glycolipid (trehalose dimycolate) related to cord factor, although itself inactive, has conferred antitumor properties on several otherwise ineffective materials, including bacterial endotoxins. In the present work, original P3 (isolated from Mycobacterium tuberculosis strain Aoyama B) and several fractions obtained similarly from different sources have been compared for ability to potentiate a particular endotoxin from a O antigen-deficient (Re) mutant of Salmonella typhimurium. All were trehalose mycolates, and all were about equally effective, despite differences in mycolic acid composition. Most significantly, one of the active glycolipids was from the fast-growing nonpathogen, Mycobacterium phlei, and two were monomycolates of trehalose.

Delayed Hypersensitivity and Granulomatous Response After Immunization with Protein Antigens Associated with a Mycobacterial Glycolipid and Oil Droplets

A myocardial glycolipid (P3) mixed with protein antigens in oil-in-water emulsion induced lasting delayed hypersensitivity (DH) and granulomatous inflammation after intradermal injection into guinea pigs. This did not occur when P3 and bovine serum albumin (BSA) were given in Freund's incomplete adjuvant. The oil-in-water emulsions consisted of microscopic oil droplets suspended in aqueous medium. By separating oil and aqueous phases from BSA + P3 emulsion it was shown that antigen retained with oil droplets led to DH and granuloma formation. The association of antigen with oil droplets was P3 dependent and was quantitated with 125I-labeled BSA. The same phenomenon occurred with 125I-labeled rabbit gamma-globulin (RGG) + P3 emulsion. Fluorescein-conjugated RGG was observed in a particulate state within or on oil droplets in emulsion containing P3. These physical characteristics of antigen + P3 emulsion appeared to be important for immunogenicity.

Specific suppression of immune response to a given antigen by emulsified oil droplets containing a mixture of antigen and dexamethasone phosphate.

IN attempts to explain specific suppression of the immune response to a given antigen, specific antigen receptors have been demonstrated on the surface of small populations of lymphocytes1,2. We have now investigated further the mechanisms involved, using small droplets of a mixture of an appropriate immunosuppressive agent and an antigen. We reasoned that the immunocompetent cells carrying receptors for the antigen would interact directly with the droplets and the cells would be exposed to the injurious action of the agent. Animals injected with the droplets would show a reduced response to the antigen, but normal responsiveness to other antigens.

Electron Microscopy of Mayonnaise

Laboratory- and commercially-prepared samples of mayonnaise were examined by electron microscopy in an attempt to view the protective layer around the emulsified oil droplets. Distinct, structurally-intact droplets with good contrast were observed in micrographs when mayonnaise samples were fixed with an acrolein-glutaraldehyde solution and post-fixed with Os04 and stained with uranyl acetate and lead citrate solution. Oil droplets in all mayonnaise samples possessed a continuous speckled layer on the periphery. A thin low electron-dense fibrous membrane, presumably formed during colloid milling, was noted on the surface of the water-washed droplets of commercially prepared mayonnaise. Fibrous membranes could not be detected on the surfaces of washed droplets of laboratory-prepared mayonnaise (no colloid milling). It is postulated that the speckled layers were made up of 1. coalesced low-density lipoproteins of egg yolk, and 2. microparticles from the yolk granules. The stability of the droplets may be attributed to the high degree of plasticity created by particulate matter in the speckled areas and to fibrous membrane structures on the droplet surfaces.

A Sound Velocity Method for Determining the Compressibility of Finely Divided Substances

A method is presented whereby the adiabatic compressibility of a finely divided material can be found from sound velocity and density measurements of a suspension of the particles in a liquid. The method is based on the assumption that the velocity of sound in a suspension is the same as it would be in an ideal solution of the two substances. This is verified experimentally by measurements of sound velocity in kaolin-water suspensions and xylene-water emulsions, and the method is illustrated by the determination of compressibility of the oil droplets in an oil emulsion and of the blood corpuscles in horse blood. Considerable accuracy is attainable for materials which are not too incompressible compared to the suspending liquid.