Saturated Aqueous Phase Research Articles

Study of the biological activity of essential oils-water mixtures

This study aimed to investigate the biological activity of aqueous mixtures of two essential oils. The mixtures were prepared by mixing certain amounts of lavender and clove oils with distilled water at room temperature. In the case of lavender oil, a relatively clear saturated aqueous phase was obtained after mixing with an excess of the essential oil. The clove oil formed stable oil-in-water emulsions. The antibacterial activity of the samples was tested against two model bacterial strains. The growth of the Gram-negative Escherichia coli K12 and the Gram-positive Bacillus subtilis 3562 was determined in 96-well microplates. A more prominent inhibition activity against E. coli K12 strain compared to B. subtilis 3562 for both oil-water mixtures was observed. A disk diffusion test indicated growth inhibition by the lavender oil during the tests against the Gram-positive strain (zones of around 11.7 mm) while clove oil inhibited both bacteria (12 mm - B. subtilis 3562 and 13.66 mm - E. coli K12). The DPPH free radical method showed no antioxidant activity for the aqueous solution of lavender oil. The pure lavender oil exhibited negligible activity compared to the gallic acid reference solution, the clove essential oil, and its emulsion. A quantitative relationship between the content of cloves essential oil in the emulsion and its radical scavenging capacity was demonstrated.

Interaction of low salinity surfactant nanofluids with carbonate surfaces and molecular level dynamics at fluid-fluid interface at ScCO2 loading

HypothesisThe advanced low salinity aqueous formulations are yet to be validated as an injection fluid for enhanced oil recovery (EOR) from the carbonate reservoirs and CO2 geosequestration. Interaction of various ionic species present in the novel low salinity surfactant nanofluids with scCO2/CO2 saturated aqueous phase interface and at the interface of CO2 saturated aqueous phase/mixed wet (with CO2 and Decane) limestone surface at the conditions of low salinity at reservoir conditions are to yet to be understood. ExperimentsThis study, carried out for the first time in low salinity at scCO2 loading conditions at 20 MPa pressure and 343 K temperature, comprises of wettability study of the limestone surface by aqueous phase contact angle measurements using ZrO2 nanoparticles (in the concentration range of 100–2000 mg/L) and 0.82 mM Hexadecyltrimethylammonium bromide (CTAB) surfactant. Molecular dynamics simulations results were used to understand the underlying mechanism of wettability alteration and interfacial tension (IFT) change. FindingsThis study reveals that a low dosage (100 mg/L) of ZrO2 nanoparticles forming ZrO2-CTAB nano-complexes helps in wettability alteration of the rock surface to more water-wetting state; certain ionic species augment this effect when used in appropriate concentration. Also, these nano-complexes helps in scCO2/CO2 saturated aqueous phase IFT reduction. This study can be used to design advanced low salinity injection fluids for water alternating gas injection for EOR and CO2 geosequestration projects.

Estimating n-octanol-water partition coefficients for neutral highly hydrophobic chemicals using measured n-butanol-water partition coefficients

Direct measurement of the n-octanol partition coefficients (KOW) for highly hydrophobic organic chemicals is extremely difficult because of the extremely low concentrations present in the water phase. n-Butanol/water partition coefficients (KBW) are generally much lower than KOW due to the increased solubility of solute in the alcohol saturated aqueous phase, and therefore become easier to measure. We measured the KBW for 25 neutral organic chemicals having measured log KOWs ranging from 2 to 9 and 4 additional highly hydrophobic chemicals, with unmeasured KOWs, having estimated log KOWs ranging from 6 to 18. The measured log KBW and log KOW values were linearly related, r2 = 0.978, and using the regression developed from the data, KOWs were predicted for the 4 highly hydrophobic chemicals with unmeasured KOWs. The resulting predictions were orders of magnitude lower than those predicted by a variety of computational models and suggests the estimates of KOW in the literature for highly hydrophobic chemicals (i.e., log KOW greater than 10) are likely incorrect by several orders of magnitude.

3D printed dielectric ceramic without a sintering stage

This paper presents for the first time the fabrication of dielectric ceramic parts by 3D printing without sintering. The printable paste was prepared by mixing a carefully selected amount of water-soluble Li2MoO4 powder with water. A viscous mixture of solid ceramic particles and saturated aqueous phase was formed with a solid content of 60.0 vol.%. Printing of the sample discs was conducted with material extrusion using a low-cost syringe-style 3D printer. The consolidation and densification of the printed parts occurred during both printing and drying of the paste due to extrusion pressure, capillary forces, and recrystallization of the dissolved Li2MoO4. Complete drying of the paste was ensured by heating at 120 °C. The microstructure showed no delamination of the printed layers. Relatively high densities and good dielectric properties were obtained, especially when considering that no sintering and only pressure from the extrusion was employed. This approach is expected to be feasible for similar ceramics and ceramic composites.

Temozolomide-loaded PLGA nanoparticles to treat glioblastoma cells: a biophysical and cell culture evaluation

Objectives: Current chemotherapies for brain glioblastoma do not achieve sufficient drug concentrations within tumors. Polymeric nanoparticles have useful physicochemical properties that make them promising as nanoparticle platforms for glioblastoma drug delivery. Poly[lactic-co-glycolic acid] (PLGA) nanoparticles encapsulating temozolomide (TMZ) could improve localized delivery and sustained drug release to glioblastomas.Methods: We investigated three different procedures to encapsulate TMZ within PLGA nanoparticles. We studied the biophysical features of optimized nanocarriers, including their size, shape, surface properties, and release characteristics of TMZ. We evaluated the antiproliferative and cytotoxic effects of TMZ-loaded PLGA nanoparticles on U87 MG glioblastoma cells.Results: A single emulsion technique using a TMZ saturated aqueous phase produced nanoparticles ≤200 nm in size allowing a maximal drug loading of 4.4% w/w of polymer. There was a bi-phasic drug release pattern, with 80% of TMZ released within the first 6 h. Nanoparticles accumulated in the cytoplasm after effective endocytosis. There was no significant difference in cytotoxic effect of TMZ encapsulated within PLGA nanoparticles and free TMZ.Conclusions: PLGA nanoparticles are not suitable as carriers of TMZ for glioblastoma drug delivery on account of the overall high IC50 values of glioblastoma cells to TMZ and poor loading and encapsulation efficiencies. Further biotechnological developments aimed at improving the loading of TMZ in PLGA nanoparticles or co-delivery of small molecule sensitizers to improve the response of human glioblastoma cells to TMZ are required for this approach to be considered and optimized for future clinical translation.

Visualization of improved sweep with foam in heterogeneous porous media using microfluidics

We demonstrate the use of foam to divert flow from high permeable to low permeable regions in a PDMS heterogeneous porous microfluidic system. Foam is generated using a flow-focusing microfluidic device with co-flowing gas and aqueous surfactant streams. Foam quality (gas fraction) is modulated by adjusting the flow rate of the aqueous surfactant solution while keeping the gas inlet pressure fixed. The foam is then injected into an aqueous-solution filled heterogeneous porous media containing a high and low permeable region and sweep of the saturated aqueous phase is monitored. Compared with 100% gas injection, surfactant-stabilized foam is shown to effectively improve the sweep of the aqueous fluid in both high and low permeable regions of the porous micromodel. The best performance of foam on fluid diversion is observed in the lamella-separated foam regime, where the presence of foam can enhance gas saturation in the low permeable region up to 45.1% at the time of gas breakthrough. The presented results are useful in understanding and designing foam injection in porous underground formations for aquifer remediation and enhanced oil recovery processes.

A Methane−Water Model for Coarse-Grained Simulations of Solutions and Clathrate Hydrates

Methane is the prototypic hydrophobic molecule; it has an extremely low solubility in liquid water that leads to phase segregation. On the other hand, at moderate pressures and room temperature, water and methane form hydrate clathrate crystals with a methane to water ratio up to a 1000 times higher than the saturated aqueous phase. This apparent dichotomy points to a subtle balance between the strong water-water hydrogen bonding, responsible for the hydrophobic effect, and water-methane attraction. Capturing these nuances with molecular models requires an appropriate balance of intermolecular interactions. Here we present such a coarse-grained molecular model of water and methane that represents each molecule by a single particle interacting through very short-range interaction potentials. The model is based on the monatomic model of water mW [Molinero, V.; Moore, E. B. J. Phys. Chem. B 2009, 113, 4008] and is between 2 and 3 orders of magnitude more computationally efficient than atomistic models with Ewald sums. The coarse-grained model of this study reproduces the solubility and hydration number of methane in liquid water, the surface tension of the water-methane interface and the equilibrium melting temperature of methane hydrate clathrates with structures sI and sII. To the best of our knowledge this is the first force-field, atomistic or coarse-grained, that reproduces these range of properties of liquid and solid phases of water and methane, making it an efficient and accurate model for the study of the mechanisms of nucleation and growth of clathrates. We expect that the results of this work will also be useful for the modeling of the hydrophobic assembly in aqueous solutions and the development of coarse-grained models of biomolecules with explicit solvation.

Synthesis and Characterization of mPEG−PLA Prodrug Micelles

Polymeric prodrugs of mPEG-PLA-haloperidol (methoxypoly(ethylene glycol)-b-poly(lactic acid)) can self-assemble into nanoscale micelle-like structures in aqueous solutions. mPEG-PLA-haloperidol was prepared and characterized using 1H and 13C NMR. The conjugation efficiency was found to be 64.8 +/- 21%. Micelles that form spontaneously upon solubilization of the mPEG-PLA and the polymeric prodrugs in water were characterized using a variety of techniques. The mPEG-PLA and prodrug micelles were found to have diameters of 28.73 +/- 1.45 and 49.67 +/- 4.29 nm, respectively, using dynamic light scattering (DLS). The micelle size and polydispersity were also evaluated with cryogenic transmission electron microscopy (cryo-TEM) and were consistent with the DLS results. Cryo-TEM and proton NMR confirmed that the micelles were spherical in shape. DLS was also used to determine the aggregation numbers of the micelles. The aggregation numbers ranged from 351 to 603. The change in aggregation number was dependent on the total drug incorporation into the micelle core. Critical micelle concentrations were determined for the various micelle/drug formulations and found to range from 3 to 14 microg/mL. Finally, drug was incorporated into the micelle core using the conjugate, free drug with a saturated aqueous phase during production, or a combination of both techniques. Drug incorporation could be increased from 3% to 20% (w/w) using the different formulations.

Experimental Determination of the Deliquescence Relative Humidity and Conductivity of Multicomponent Salt Mixtures

ABSTRACTThe conductivity of hygroscopic salt deposits containing Na+, K+, NO3– and Cl– ions was measured in air as a function of relative humidity at constant temperatures. The deliquescence relative humidity (DRH) of multicomponent salts containing Na+, K+, NO3– and Cl– was also determined experimentally. The results of the conductivity experiments show that the conductivity of initially dry salt deposits start to increase after reaching a relative humidity value that is 15 to 20% lower than the DRH of the salt. When the DRH is reached, the conductivity increases dramatically as the salt dissolves and transforms into a saturated aqueous phase. The increase in conductivity at humidities below the DRH is attributed to the adsorption of water on the surface of the salt particles. Because of the increase in conductivity, the initiation of aqueous corrosion of metals in contact with hygroscopic salts may occur at a relative humidity much lower than the DRH of the salt. Thus, the onset of aqueous corrosion of metallic nuclear waste package and the drip shield may be earlier, the duration may be longer, and the temperature at which it occurs may be higher than assumed based on the DRH of the salt. The results of the DRH experiments show that the DRH of a salt mixture is usually significantly lower than that of any of its component pure salt.

Determination of the Maximum Swellability of Polymer by Monomer Using Conductivity Measurements

The maximum swellability of the polymer phase by monomer is an important parameter in emulsion polymerization. This parameter can be determined either by traditional monomer partitioning experiments or by conductivity measurements. The use of conductivity measurements to determine swellability values is new and rather simple. Compared to conventional monomer partitioning experiments it is less laborious and, in those cases where the monomer-saturated polymer phase has a higher density than the saturated aqueous phase, more accurate results can be obtained. For styrene (Sty) and methyl methacrylate (MMA), the maximum swellabilities were determined in a series of Sty-MMA copolymers by traditional monomer partitioning experiments and by conductivity measurements. From the good agreement it could be concluded that conductivity measurements indeed are a useful method of determining maximum swellability values.